Archive for February, 2008

STEERING GEARS RACK AND PINION STEERING GEARS-STEERING ASSIST-DIAGNOSTIC TIPS AUTO REPAIR HOUSTON,TX

Tuesday, February 5th, 2008

Diagnostic Solutions


STEERING GEARSKeeping Your Customers’ Vehicles on The Straight & Narrowby Gary Goms, Import Specialist ContributorModern automotive steering gears evolved from the quaint tiller-controlled steering systems used in the first automobiles to the hydraulically controlled systems now used in most import vehicles. Unfortunately, steering tillers that attached to axles with little or no steering geometry didn’t provide much steering feedback from the road surface. When vehicle speeds approached 20 mph, auto manufacturers began to incorporate more sophisticated steering systems to help the driver keep the vehicle traveling in a straight line.As vehicles became heavier and more difficult to steer, auto manufacturers developed different types of steering gears designed to change the rotating motion of the steering wheel and shaft into a lateral motion transmitted through the steering linkage to the steering knuckles and front wheels. This system has prevailed to this day.KINGPIN INCLINATION
As steering gear technology progressed, innovations in steering geometry also aided steering gear functions. The popular introduction of kingpin inclination (KPI) during the early 1920s, for example, eased steering effort by tilting the kingpin inward at the top, so that a line drawn through the kingpin angle intersects with the center of the tire tread. KPI is also present in ball joint or MacPherson strut systems, with the angle of the upper and lower ball joints or MacPherson strut intersecting with the center of the tire tread.

KPI actually accomplishes three separate, but related, steering functions. First, KPI reduces steering effort by allowing the tire to pivot on the center of its tread rather than be swung around the axis of a vertical kingpin. Second, KPI greatly reduces the probability that a wheel striking a pothole may suddenly spin the steering wheel out of the driver’s hands. Third, KPI actually lifts one side of the vehicle and lowers the other as the wheels are turned. This lifting effect, combined with caster angle, forces the front wheels to return to a straight-ahead position. For all of the above reasons, steering effort increases and the steering wheel becomes more sensitive to road shock whenever offset custom wheels are installed on a vehicle.

THE ROLE OF CASTER ANGLE
Caster angle also plays a function in all steering gear systems. Positive caster angle can be easily visualized in the backward tilt of a bicycle’s front fork. Positive caster angle, of course, allows the bicycle to steer itself when the rider takes his hands off the handlebars. Although some auto manufacturers may employ negative caster angle to accomplish the same purpose, caster helps force the front wheels to return to center when the driver releases the steering wheel.

CONVENTIONAL STEERING GEARS
Although conventional parallelogram steering linkage systems are being replaced by the more modern rack and pinion steering gears, many heavier vehicles such as luxury sedans and pickup trucks still use conventional steering gears. Early steering gears were crude, bronze-bushed units that required a great amount of steering effort to turn the wheels. As vehicles became heavier, ball and needle-roller bearings were used to reduce friction in the steering gear assembly. In addition, a recirculating ball-bearing worm gear assembly was introduced that greatly reduced friction between the worm gear mounted on the steering gear input shaft and the sector gear mounted on the steering output shaft.

As vehicle speeds increased, it became very important for the steering gear to transmit a sense of “road feel” to the driver. Without a fine-tuned sense of steering wheel center, it became difficult for a driver to drive in a straight line at high speed. To accomplish this, engineers designed a worm and sector gear that would develop zero clearance or lash when the steering gear operated in the centered or straight-ahead position. The fact that the steering gear ‘tightens” up when the front wheels are in the straight-ahead position gives the driver a much finer sense of when the vehicle is tracking in a straight line.

As the wheels are turned, the steering gear rolls off the “high spot” and develops clearance between the worm and sector gears. This added clearance reduces friction and helps the front wheels return to the straight-ahead position when the driver releases the steering wheel. In addition, the high spot in the steering gear tends to stop or hold the steering gear in the straight-ahead position by increasing friction between the worm and sector gears. This particular feature helps prevent the driver from over-steering the vehicle.

RACK-AND-PINION STEERING GEARS
Rack and pinion steering gears were popularly introduced into the import market during the 1950s because they provided fast steering wheel response and had fewer parts. In this system, a rack gear is attached to the right and left steering knuckles by tie rods that swivel to allow vertical movement in the suspension system. The pinion gear, of course, is attached to the steering shaft and moves the rack in a lateral direction in response to steering wheel input. Like the conventional steering gear, the rack and pinion is machined to decrease gear lash as the steering wheel returns to the center position.

STEERING ASSIST
Steering assist systems incorporate a hydraulic pump driven by an engine accessory drive belt to provide pressure to a steering assist cylinder attached to the sector gear in conventional systems or the rack gear in rack and pinion systems.

To provide full steering assist, the power steering pump must produce at least 1,000 psi pressure upon demand. Because a power steering pump is used only a small percentage of time, the pump is equipped with a hydraulic boost or computer-controlled, pulse-modulated valve assembly that allows it to free-wheel during highway driving. To fine-tune steering wheel response, the steering gear shaft is equipped with a torsion bar that opens a metering valve as torque is applied to the steering wheel. Due to the action of the torsion bar, the amount of oil pressure metered to the steering assist cylinder is directly proportional to the torque being applied to the steering wheel.

The metering valve assembly is very sensitive because it’s often equipped with compressible reaction discs that further increase the steering gear’s sensitivity to steering wheel torque. Some manufacturers, such as Honda, have used axle-driven mechanical systems that limit power steering assist to low-speed driving situations. In other applications, steering pump pressure may be controlled by using a pulse-width modulation system that varies pressure in response to steering wheel demand and highway speed.

DIAGNOSTIC TIPS
On high-mileage vehicles with a steering wander complaint, the sector gear lash might require adjusting to eliminate excessive lash between the worm and sector gears. Early manual rack and pinion gears also have a similar adjustment that reduces lash between the pinion and rack gears.

A steering gear may also transmit steering feedback to the driver only when it’s installed in the centered position. In most cases, a four-wheel alignment may be required to recenter the steering gear. The first step is to always make sure that indexing marks on the steering wheel and steering shaft are aligned. The last step is to adjust front and rear toe angles to correspond with the vehicle’s centerline or thrust angle. When removing the steering wheel, always follow the manufacturers’ instructions regarding the disarming of the air bag and preventing damage to the air bag clock spring.

Any power steering gear can develop a “lack of assist” complaint. Generally speaking, a worn power steering pump is usually indicated if steering assist deteriorates as the steering oil begins to warm up and lose viscosity. In contrast, some rack and pinion steering gears may develop an intermittent condition called “morning sickness.” This particular lack of steering assist is caused by the metering valve oil seals wearing grooves into the soft aluminum steering gear housing. As the steering gear oil warms up, the valve assembly reseals itself to the housing and restores steering assist. Because special tools and expertise might be required to rebuild a steering gear, it’s more cost-effective to install a new or remanufactured gear than to repair or rebuild an old one.

Last, it’s always important to use application-specific power steering fluid in import applications. In the case of Honda, using non-OE specification fluid can ruin the steering gear seals. In other applications, using the wrong fluid or mixing fluids can cause the steering fluid to foam, which may cause a howling noise and temporary reduction of steering assist.

CAR-AUTO-ENGINE P0401 ENGINE CODES EGR PROBLEMS-NOx EMMISSIONS PROBLEMS-HOUSTON,TX

Friday, February 1st, 2008

EGR ISSUES


Dealing with P0401 Codesby Bob DowieExhaust gas recirculation (EGR) has been used for years to control combustion temperature to prevent spark knock as well as control NOx emissions. For the most part, these systems were trouble-free and required service only if you were dealing with a spark knock issue, or if the valve opened too early, resulting in a tip-in acceleration stumble, or the more common, bad idle quality caused by the valve not closing completely at idle. As emission controls got tighter, and with the advent of OBD II, things started to change. We not only saw additional driveability complaints, but we also had the check engine light (CEL) telling the customer there was an emissions failure that had to be dealt with for the good of the environment and, in most states, to pass the annual vehicle inspection. In this article, we’ll take a look at some Honda EGR issues, which have also plagued the Acura line.

We’ll start with the four-cylinder Accord engines. While there have been some reports of problems with the Civic, problems with the Accord have been the most prevalent. Driveability complaints are more common than check engine lights on these models through the ‘90s. What you’ll be faced with is a stumble complaint, which is actually a misfire at part-throttle, that’s most prevalent on initial acceleration when the EGR valve is commanded to open. It feels almost like a bad wire and happens just when you’d expect a secondary ignition problem — part-load acceleration.

The cause of the misfire is an excess of recycled exhaust gasses in one or more cylinders. The cause of this excess flow is actually plugged passages in the manifold leading to the other cylinders. When there is no flow to those cylinders, the remaining cylinders receive all the exhaust gasses, which cause the miss. This problem has caused a great deal of frustration with techs, resulting in a lot of misdiagnosis. That’s not very surprising considering how well this problem mimics a secondary ignition problem. Then, to further confuse the issue, if there is a CEL, it’s often for the misfire and not the EGR system. Up until 1998, when the electronically controlled EGR valves were introduced, Honda looked at the EGR lift sensor to confirm that the valve received vacuum and opened, and that flow was taking place. Since the valve is opening, the ECU figures all is well there, but it’s well trained to pick up a misfire and is quick to report any problem that would hurt the catalytic converter.

MISDIAGNOSIS WOES
Often the combination of the obvious miss and the misfire code will send techs down the wrong path. Not that there’s anything wrong with checking the ignition system, but it takes only minutes to confirm if it’s the EGR system giving you a problem and not a bad wire or plug. Simply disable the valve and do a road test.

You’ll probably get a check engine light but, if the miss is gone, you’ll know for sure that the EGR system is the culprit. But don’t overlook checking the ignition components. It’s good to know the miss is fixed, but there’s never a bad time to bring the car up-to-snuff on maintenance items. Plus, you wouldn’t want the car coming back with a bad cap, wires or plugs next week if you could’ve taken care of those items now.

If disabling the EGR eliminated the miss, it’s time to clean out the passages. The procedure differs slightly depending on the year of the vehicle. The early cars used a blind core plug to seal the manifold runner EGR port after machining. We’ve found that the best way to remove these plugs is to drill a small hole partially into the plug, and using a self-tapping screw, or tapping the hole for a machine screw and using a small slide hammer, to pull them out. Partially drilling them will allow you to reuse the plugs if no replacements are on hand. Replacement plugs are available and there’s actually a kit from Honda that includes the tools and plug.

Needless to say, caution is required when drilling or tapping. Grease up the drill bit and tap to catch as many of the chips as possible. Using a shop vac is a much better choice than compressed air to keep the area clean as you work. With the plugs removed, the blockage will be obvious and can be easily dislodged using a stiff wire and carb cleaner. Be sure to clean the entire port again to keep the vacuum running. This procedure is well outlined in service bulletin #98-074, which should be available on your service information system.

The next era of four-cylinder cars saw the plugs replaced by a plate covering the EGR channel as well as the ports. This was a big improvement that eliminates the need to drill and allows us to better clean out any carbon buildup in the channel and the ports. Accessibility isn’t a problem, but the injectors will have to be removed. To be safe, you may want to have injector seals available, but they can often be reused. The latest of the four cylinders use a two-piece intake plenum with the EGR passages cast into the upper section. These cars don’t seem to suffer from the misfire problems of the earlier cars, but are more apt to have flow problems that will be picked up by the more observant OBD system setting a check engine light. To access the EGR ports and channel on these engines, split the intake and use a stiff wire to clean out the ports — a very similar procedure to the V6s that we’ll talk about next.

In recent years, EGR problems seem to be most prevalent on V-6 engines used in the popular Odyssey minivan, Accords and SUVs; only the worst cases will present driveability symptoms. It will be the check engine light providing the motivation for the customer, using the same enhanced code-setting criteria as the late-model four cylinders.

When Honda went to the electronically controlled sensor, they were now able to command the amount of lift, monitor the actual amount of lift and look at the MAP sensor making sure it had the expected effect on air flow. If anything unexpected happens on two trips, the check engine light will let the customer know.

The EGR passages on the six cylinders are in the upper section of the intake manifold. Some of the gaskets are reusable, but if you’re going in, the safe bet is to at least have a throttle body gasket on hand. To get started:

  1. Remove the plastic throttle body and manifold covers, and remove the throttle body, leaving the electrical connectors, hoses and cables attached. Naturally, this is a great time to service the throttle plate.
  2. Remove the upper manifold with the PCV attached.
  3. With the manifold off, remove the chamber on the opposite side of the manifold from the throttle body along with the intake air temp sensor, PCV hose and brake booster nipple. These are removed to provide better access for cleaning the manifold when you’re done.
  4. Turning the manifold over, tape off the intake ports leaving the EGR port exposed.
  5. Using a 8mm (5/16”) drill bit as a hand-held ream, clean out the port. If you’re installing the update kit, now is when you’ll drill the manifold using the bit provided; be sure to follow the cautions included with the kit so as not to damage the manifold.
  6. The next step is a thorough cleaning, flushing all the ports and intake runners from both directions. If you’re doing the update, now is also the time to install the EGR pipe.
  7. Finish up by inspecting the EGR port in the manifold base and cleaning as required. This is best done with the EGR valve removed.

The aforementioned update kit is fully explained in Honda service bulletin #05-026, which also details the 8-year, 80,000-mile warranty extension for the EGR system. Many of these cars have been updated, but you’ll still see plenty of them with well over 80,000 miles that will be experiencing this problem, as well as some vehicles that aren’t covered in the bulletin. Nonetheless, the bulletin is a good resource to have.

CAUSES OF A P0401 CODE
While port restrictions are the most common cause of a P0401 code, that’s not the only reason you’ll see it. With the older vacuum-controlled EGR valves, there have been issues with the vacuum-switching valves being intermittent. Testing is straight-forward. With the engine running, be sure vacuum is available at the inlet side of the valve, then hook up the gauge to the hose leading to the EGR valve.

With the electrical connecter unplugged from the switching valve, introduce battery voltage to the black/yellow wire and apply ground to the red wire at the valve side of the electrical connector. If all is well, you’ll show vacuum on the gauge. As I said, these valves have a reputation for being intermittent, so repeat the test in quick succession looking for slow or no response on the gauge.

The electronic EGR valves are quite reliable but certainly haven’t been trouble-free; the problems we’re seeing with them are more about them sticking and not doing what they’re told. The good news is they’re not hard to diagnose when you know what you’re looking at. Let’s look at the connector on a 2002 model. We have five wires that handle valve operation and reporting; the valve is power-side controlled with a duty cycle signal from the ECU through the pink wire that gets its ground from the black wire.

On the reporting side, the yellow and blue is the 5V reference signal from the ECU for the position sensor, the green and black is ECU ground, with the white and black sending the signal back to the ECU, letting it know how the EGR is responding to direction. An increase in operational duty cycle should result in a smooth increase in reporting voltage with no dropouts. Many scan tools will let you look at and log command and reporting data on a road test. Otherwise, with good access, it’s not difficult to back-probe the connector and get the same info on a multi-channel graphing meter.

We can also use what we know about the wiring to check for blocked passages and the basic operation of the valve. With the electrical connector disconnected, the valve will open by putting battery power to the terminal that the pink wire is connected to and grounding the black wire terminal. If the ports are clear and the valve is working, the engine should quickly get rough or stall, and smooth out when the valve is closed.

When diagnosing a driveability problem, it’s important to keep in mind if you have a problem on light acceleration at low RPM, when the EGR is commanded on, suspect the EGR system. Or, an intermittent rough idle may be the result of the valve not completely closing. Otherwise, the EGR system shouldn’t be suspected.

If I can leave you with one solid tip for diagnosing and repairing EGR problems on the Honda line of vehicles, it’s to check your service information system for service bulletins. Honda does a great job of making this information available to the aftermarket, and it’s just foolish not to take advantage of it. If you’re not going online, checking for bulletins and making full use of services like iATN, import-car.com and OEM info like that available from Honda (www.techinfo.honda.com), you’re just leaving too much good information untapped. The way things are going, you won’t be able to afford doing that much longer.

AUTO-CAR-FUEL-INJECTORS-DIAGNOSTIC-SERVICE-ENGINE PROBLEMS-HOUSTON,TX

Friday, February 1st, 2008

Is There Enough Pressure?


Fuel Injection Diagnosis & ServiceBy Larry Carley, technical editorOne of the first questions that should always be asked — and answered — when diagnosing a fuel-related complaint on a fuel injected engine is, “What is the fuel pressure?”

All too often, technicians assume fuel pressure is “good” without actually measuring it with a gauge. If the engine runs, they assume the injectors are getting adequate fuel pressure. If the engine cranks but won’t start, and they depress the service valve on the fuel rail and some fuel squirts out, they assume the injectors have pressure. They do, but the question remains, “How much pressure?”

For the engine to start and run smoothly with no stalling, hesitation or misfiring, the injectors have to deliver the proper amount of fuel with every squirt. This is especially important on late-model engines with sequential fuel injection. One bad injector will cause a noticeable misfire and usually set a P030X misfire code (where X represents the cylinder that is misfiring). On older engines where the injectors are all fired simultaneously, the good injectors can often compensate for one or two bad injectors. Even so, for the engine to run right, fuel pressure to the injectors is critical as is the volume of fuel delivered by each injector when it fires.

The fuel calibration curves in the powertrain control module (PCM) are based on OEM dyno testing using a new engine. Fuel pressure is within a specified range for that engine, and the injectors are all clean and new. The adaptive fuel control strategies that are built into a PCM that allow it to adjust short term and long term fuel trim to compensate for variances in fuel pressure and fuel delivery can maintain the correct air/fuel ratio — but only within certain limits. If an injector becomes clogged with fuel varnish deposits and fails to deliver its normal dose of fuel when it is energized, or fuel pressure to the injector drops below specifications because of a weak fuel pump, plugged fuel filter or leaky fuel pressure regulator, the PCM may not be able to increase injector duration enough to offset the difference. This can leave the air/fuel mixture too lean, causing the cylinder to misfire.

It’s All About Fuel Pressure
According to Jim Linder of Linder Technical Services (a provider of fuel injection training) in Indianapolis, IN, fuel pressure is probably the most critical factor in the fuel injection system. Linder says that only a 1 to 3 psi change in fuel pressure can often cause noticeable driveability problems. He says the first thing technicians should always check when confronted with a driveability or emissions problem is fuel pressure. Look up the fuel pressure specifications for the vehicle, hook up a gauge and check the pressure with the key on, engine off, then again with the engine running. If pressure is not within specifications, there’s a problem that will require further diagnosis.

On certain Jaguar engines, for example, the factory spec calls for 37 psi of fuel pressure. If you see 36 psi or 38 psi, you need to replace the fuel pressure regulator.

Fuel Volume Is Just As Important
The volume of fuel delivered by the fuel pump to the injectors is also critical. Some pumps may develop adequate fuel pressure when the engine is at idle or running at low speed, but the pump isn’t spinning fast enough to keep up with the engine’s fuel requirements at higher speeds. This causes the fuel mixture to lean out and the engine to misfire or lose power.

The old rule of thumb that says a “good” fuel pump will flow about a pint of fuel in 15 seconds (half a gallon per minute) still holds true, but some engines need more than this. So the fuel delivery specifications also need to be looked up to see if the pump is delivering an adequate supply of fuel to the engine.

A fuel flow meter is the most accurate means of measuring fuel delivery. The floating ball on the meter shows the fuel flow in gallons per minute (gpm).

The flow meter can be hooked up to the supply line that runs to the fuel rail to measure flow. But Linder says a better method for checking fuel flow and pump capacity is to hook up the flow meter to the return line that runs from the fuel pressure regulator back to the fuel tank. Then check the return flow at idle, 2,500 rpm and 5,000 rpm.

The volume of fuel flowing through the return line will drop as engine speed increases because more fuel is flowing through the injectors. Even so, the return flow for a good fuel pump with adequate pumping capacity at 5,000 rpm should still be about half the volume it had at idle (say 0.23 gpm versus 0.46 gpm). If the return flow at 5,000 rpm drops to 10% or less of the idle return flow rate, the fuel pump probably does not have enough reserve capacity to keep up with the engine when the engine is under load. The weak pump will starve the engine for fuel, causing it to misfire and lose power.

Get The Right Replacement Pump
Many parts suppliers list flow rates for their fuel pumps. But the rates don’t necessarily correspond to the actual fuel flow rates on a vehicle because the pumps are rated by pumping fuel into a container. There is no fuel filter or fuel pressure regulator in the system to create resistance to flow. Consequently, a pump with a catalog rating of 0.6 gpm may only flow 0.5 gpm when installed on a vehicle.

What’s more, some parts suppliers have over-consolidated their fuel pump lines to reduce the number of SKUs needed to provide broad market coverage. Pump capacities can always be higher than specifications, but should never be lower. So if you get a pump that is flow rated at 0.4 gpm and you install it in a vehicle that requires 0.5 or 0.6 gpm, the pump may supply enough fuel at idle and low rpm, but may starve the engine at higher loads and speeds. Yet it is not a “bad” pump — just an under-rated pump for the application.

Fuel Pressure Regulator Problems
The fuel injectors can’t flow normally if they have low fuel pressure due to a bad fuel pressure regulator. If the spring inside the regulator has weakened with age, if the valve or diaphragm that controls return flow is leaking, or the vacuum supply hose to the regulator is leaking, loose or plugged, it will affect fuel pressure in the fuel supply rail.

If fuel pressure is low, disconnect the vacuum hose to the regulator. You should see an increase in pressure if the regulator is not leaking. No change would indicate a bad regulator. Likewise, you can pinch or block the return line temporarily to see if pressure goes up. If it does, it means the regulator is bypassing too much fuel back to the tank and needs to be replaced.

Also, check the vacuum hose to the regulator for the presence of fuel inside the hose (there should be none). Fuel in the hose means the diaphragm inside the regulator is leaking and the regulator needs to be replaced.

Dirty Injectors
Another common problem with fuel injectors is the buildup of fuel varnish deposits in the nozzle that restrict fuel flow or disrupt the injector’s spray pattern. On many late-model engines, the shape and direction of the spray pattern is critical for clean combustion and good performance. If the injector nozzle is dirty, the pattern may be distorted or deflected to one side, causing a lean spot in the combustion chamber that can cause misfire, or even preignition or detonation.

It doesn’t take much of a restriction in an injector to lean out the fuel mixture. Only an 8% to 10% restriction in a single fuel injector can be enough to upset the air/fuel mixture and cause a misfire. Gasoline contains waxy compounds that can leave varnish deposits in the injectors when the fuel evaporates. These deposits tend to form after the engine is shut off. Heat from the engine causes residual fuel in the injector tips to evaporate.

Gasoline is supposed to contain enough detergent to prevent these deposits from sticking and accumulating in the injectors. But guess what? Not all gasolines are the same. Some brands contain much lower levels of detergent than others. Consequently, filling up with the cheapest gas one can find may not be the best idea in the long run — especially for short-trip, stop-and-go city driving that causes deposits to form at a much faster rate. To counter this, a growing number of gasoline retailers (Chevron, Conoco, Kwik Trip, Shell, Texaco, 76 and others) now comply with “Top Tier” standards that call for higher levels of detergent to keep injectors clean.

On four cylinder engines, the #2 and #3 injectors are in the hottest location and tend to clog up faster than the end injectors on cylinders #1 and #4. The same applies to the injectors in the middle cylinders in six- and eight-cylinder engines. The hotter the location, the more vulnerable the injector is to clogging from heat soak.

The cure for dirty injectors is to clean them (on-car, or off-car with special injector cleaning machine), or to replace them if cleaning fails to restore normal flow rate and nozzle pattern.

Fuel Injector Electrical Checks
The solenoid at the top of the injector creates a magnetic field that pulls the injector pintle up when the injector is energized. The magnetic field must be strong enough to overcome the spring pressure and fuel pressure above the pintle, otherwise the injector may not open all the way or not open at all. Shorts, opens or excessive resistance in the injector solenoid can all cause problems.

One way to check the injectors is with an ohmmeter (key off). Disconnect the wiring connector from each injector, and measure the resistance between the injector’s terminals. Look up the specifications, don’t guess. Some specs may call for 2 to 3 ohms of resistance (typical for “peak and hold” injectors) while others require 12 to 16 ohms of resistance (“high resistance” injectors). The specs are fairly narrow, and with good reason. So if the factory specifications call for 12 to 16 ohms of resistance, and you find several injectors that are only a few ohms higher or lower, the injectors should probably be replaced. And if the injector resistance readings are significantly higher or lower than specifications, there’s no question they need to be replaced.

On GM vehicles with Multec injectors, the minimum resistance must be at least 12 ohms. Anything less means the injector is bad and needs to be replaced.

Another method for finding weak injectors if you don’t have specs is to measure and compare the resistance of all the injectors. If you find one or two that are noticeably higher or lower than the others, they probably need to be replaced.

Injector Scope Checks
If you have an oscilloscope with a low amp probe, you can also observe the current flow through the injectors with the engine running. You don’t have to unplug anything. Just clamp the amp probe around one of the injector connector wires.

When the PCM energizes the injector, current starts to flow through the circuit. This causes the waveform on the scope to ramp up. When current reaches about 70% of maximum, the injector usually opens, creating a bump in the pattern. When the PCM opens the ground circuit to turn the injector off, the pattern drops back to zero.

On engines that have the low resistance peak-and-hold style injectors, the scope will typically show a pattern with a sharp peak that drops to a plateau until the injector turns off, then it spikes again (two peaks total in the pattern). The peak is typically at 4 amps, and the hold (plateau portion of the pattern) is at 1 amp.

On high resistance injectors, a shorted injector that fails to open won’t produce a bump in the pattern. And if you see a sharp vertical rise in the current pattern, it means the injector is bad. A shorted injector can sometimes pull down the PCM driver circuit, preventing other injectors from firing depending on how the PCM driver circuits are configured.

On most vehicles, the injectors receive battery voltage when the ignition is on, and the PCM driver circuit provides the ground connection to turn the injectors on and off. If you have a dead injector, therefore, one of the first things to check would be voltage at the injector terminal. If it is less than battery voltage, there may be high resistance in the connector or wiring harness. If more than one injector is getting low voltage, the fault may be a bad injector power supply relay.

When the PCM energizes (grounds) the injector circuit, the voltage reading on the supply side should drop to zero as long as the injector is energized. This verifies the PCM ground drive circuit is working and that current is flowing through the injector.

When the PCM opens the injector circuit, it creates a momentary voltage spike, which can be seen on an oscilloscope if you hook up the scope to the injector circuit. When the injector pintle closes, it creates a little bump in the scope pattern, which should be consistent from one pulse to the next. If the scope shows multiple bumps or the pattern is changing, it means the injector pintle is sticking, or the injector is dirty.

Flow Matching Injectors
If you have an injector cleaning machine with graduated cylinders, you can flow match injectors for optimum performance. New OEM injectors may show as much as 4 to 5% from one another. Once flow rates start to vary more than about 5%, you can get noticeable driveability problems on many late-model engines. For best performance, most experts recommend flow matching all of the injectors to within 2% of each other.


Subaru Fuel Injector Removal Procedures When removing and/or replacing the fuel injector(s), it’s imperative that the below instructions be strictly followed. Failing to do so may result in damage
to the injector(s).Applicability: All Legacy, Impreza and SVX models.

Note: Pliers or any other tools not specified in these instructions should not be used under any circumstances to prevent damage to the fuel injector(s).

Fuel Injector Removal:

  1. Disconnect the fuel pump connector. Start the engine and allow the engine to stall. Crank the engine for five seconds and turn the ignition switch to the off position.
  2. Remove the air cleaner upper case, air flow meter and the air inlet boot as an assembly. On SVX vehicles, also remove the power steering hose tie-wrap on the right side of the engine.
  3. Remove the fuel injector cap(s), being very careful not to misplace the rubber spacer(s) fitted between the cap(s) and the injector(s). The rubber spacer(s) must be reinstalled with the new injector(s). Refer to Figure 1.
  4. Using only your fingers, turn the fuel injector(s) 90°. The fuel injector(s) connectors on both sides of the engine should be pointed toward the front of the vehicle. See Figure 2.
  5. Using a large flat screwdriver with a 3/8” to 1/2” blade, gently pry the injector up by twisting the screwdriver between the underside of the fuel injector connector area and the fuel injector cap mounting area. See Figure 3. Note: Be careful not to damage the fuel injector cap mounting threads.
  6. Remove the fuel injector(s) and place it in the box that contained the new injector(s) or wrap it to protect it during return shipping and handling. Any injectors received “damaged” will not be accepted.

Fuel Injector Installation:

  1. Coat the fuel injector “O” ring(s) of the new injector(s) and the mating area of the fuel rail with engine oil. Install the fuel injector(s) into the fuel rail and carefully push it in by hand until it’s fully seated. Make sure the injector connector is in the correct position so the injector cap can be correctly installed.
  2. Place the rubber spacer(s) back in position and install the injector cap and bolts.
  3. Reconnect the fuel pump connector.
  4. Reinstall the air cleaner case, air flow meter, air inlet boot and tie-wrap for SVX vehicles that were previously removed.
  5. Start the engine while holding the accelerator open 1/4 throttle to clear any fuel that may have dripped into the intake manifold.
  6. Carefully check each injector for leaks.

Courtesy of ALLDATA.

ELECTRICAL CIRCUIT SHORTS PARASITIC DRAW BATTERY-CAR-REPAIR-HOUSTON,TX

Friday, February 1st, 2008

Exterminating Electrical Parasites


By Glen Beanard, technical contributorAny electrical circuit that is wired “hot at all times” has the potential to become a parasite to the battery. There are some wanted parasites on the vehicle that are necessary to have, and some that are not. We’re going to find out how to “fingerprint” and track down the unwanted ones systematically.A parasitic draw on the battery means that, while the key is in the off position, something is pulling amperage from the battery. Like a glass of water that is slowly sipped on, it will run dry. The symptoms of a parasitic draw, or the customer complaints, can vary depending on the situation. Not every vehicle with a parasitic draw will come towed in with a dead battery. In fact, some may not even require jump starting to bring them in. It just depends on how low the battery is allowed to get before the next start. Intermittent electrical issues like:

  • gauges sweeping or inoperative at start up;
  • memory seats, mirrors and column not self adjusting;
  • radio presets disappearing; and
  • rough engine idle and harsh transmission shifting after first start-up in the morning are all possible symptoms of a parasitic draw on the battery. Any of those issues, and more, may have “healed” themselves by the time the customer brings it to your shop to check them out.

When the customer experiences one of these issues that could be caused by a weak battery, possibly from a draw, it can be helpful to perform a full body code scan. Clues can be found in various modules such as a P1000 in the PCM, or “battery voltage low” codes found in air bag, ABS, instrument cluster and various body controller modules. A vehicle with a battery voltage low code stored in any module should be tested for a parasitic draw.

Prepping the Patient
Getting a vehicle ready for a draw test involves a tad bit more than just hooking up an ammeter. With today’s vehicles, various modules (and lights) are awakened by simply operating a door handle. Since the awakening of modules (and lights) will suddenly cause an expected electrical draw, how are you going to access the inside of the vehicle after you determine there is an unwanted draw in the passenger area? Opening a car door at that point will bury the draw test results in a flood of amperage flow to other circuits. Before beginning a parasitic draw test, remove the key from the ignition and open all doors including the back hatch if equipped. Then, defeat the door ajar switches. For many modern vehicles, such as this 2005 Ford Explorer, this is done simply by using a screwdriver to artificially close the latches. See Photo 1.

For others, defeating the door ajar switches may mean removal of the switches from the door jam or inserting something in the door jam that artificially depresses the switch. Don’t forget to do the same for hood switches on some vehicles as well. Removing the key and defeating all door switches with the doors open will give the body control modules the illusion that you have exited the vehicle, yet you will still have full access to the interior of the vehicle for later pinpoint testing.

Next, set your ammeter up at the easiest to access (and cleanest) battery terminal. Though you could just snatch the cable off and put your ammeter in-line, I suggest some care is taken at this point. With most top post batteries anyway, it is possible to set your ammeter up without breaking the circuit with just a few simple and quick steps.

Step 1: Using a pointed lead for one tip and a gator clamp for the other tip, connect the gator clip to the cable and dig the pointed end into the top of the battery post for future foot holding. Be sure the leads are properly connected to the DVOM and that the DVOM is set to the ammeter setting. See Photo 2.

Step 2: Lift the battery cable up, the ammeter will be completing the circuit if the cable loses contact with the post. Then slide the cable over to the pointed probe that is on the top of the post. Push the eye of the battery cable down so that it is in contact with the battery post. See Photo 3.

Step 3: Lift the pointed probe over the battery cable’s eye, and back to the post outside of the eye. See Photo 4.

Step 4: Pull the battery cable away from the post and drag the pointed probe back to the mounting dent that you made in the top of the battery post. A few twists of the probe into the soft lead post, and the probe will stand up and hold itself in place for testing. See Photo 5.

For some vehicles, it might be easier to use a jumper pack set up for supplemental power while hooking up the ammeter, especially for side post batteries. For others, this little bunny hop of the test lead may be faster. But the idea here is to maintain things like radio (especially security radios), clock settings, power window settings (rather important to do so on some makes and models), and aftermarket alarm systems to reduce the unwanted stress of having to deal with a customer screaming about lost settings.

Ever have an alarm system lock out the starter and find out that the customer has no key fob for it? That’s real fun. Granted, with the nature of the problem that we might be looking for next, we just might wipe some of that stuff out during testing anyway. But remember, we don’t know for sure if we have a draw yet. So at this point, let’s not make more work for ourselves… there is still a chance we’ll find no draw after all. It’s bad enough to lose some settings when we have to, it’s worse when we later find out we didn’t have to at all.

OK, so now the ammeter is set up and we have a value showing on the meter. Wow, the meter is showing 0.59 amps. See Photo 6.

That’s a pretty hefty draw there. Is that a problem? Actually, it’s too soon to tell. Remember all that door ajar switch defeating we did a little bit ago? Why did we do that? There are some body modules on this vehicle that haven’t gone to “sleep” yet. On any given vehicle there can be a handful of modules like BCM (GEM), vehicle security, lighting control and so on that will stay awake for as long as 45 minutes after the last door handle, door switch or key-in-sense switch has been tripped. So, we need to wait about an hour before reading the ammeter. Leave the ammeter hooked up, just turn off the power switch on the ammeter and go do something else for an hour. We’ll come back to that later, just remember where we left off.

Fingerprints of a Suspect
Some techs will argue that you can use a bulb-type test light for draw testing, and some will argue that you cannot do it on today’s cars. I’m not going to sit here and tell anyone that they can’t possibly test for a draw with a test light, because I myself have done it. On the other hand, I’m not going to endorse the use of a test light for draw testing either. Even though I’m guilty of it, I will say that draw testing with a test light is unwise. If a draw is small enough, it may be missed with a test light. If it’s large enough to see with a test light, just how large is it? It’s unwise to attempt to use a test light largely because it doesn’t allow you to see the parasite’s “fingerprint.”

What I mean by a fingerprint is that different items have a signature amount of amperage that they will draw. For example, you might measure a parasitic draw of 0.15 amps at the battery. Everything that is wired hot at all times is suspect of a draw, but there might only be one item on the vehicle that will draw that exact signature 0.15 amps and also wired hot at all times. In theory, if there were a published spec you could look at of what each item draws, you could probably go straight to it off of that. But as it is, you have to hunt for it… but at least you know that you are hunting for a 0.15-amp draw. A test light hides that fingerprint from you. With a test light, what is a 0.34-amp brightness? Or a 0.25-amp brightness? How bright is “a little bright”? Have you ever had a draw go away after you’re getting close to it during testing?

If you know the signature amperage, and you’ve narrowed the suspect down, you might be able to prove to yourself what the draw is by manually stimulating a suspect module to see if its signature draw matches what you were hunting for before it “healed” itself. You can’t do that accurately with a test light.

Let’s Get Hands-On
Let’s go back and check that 2005 Explorer. After a suitable time out period, the amperage draw has reduced to 0.20 amps. See Photo 7.

That’s better; some modules have gone to sleep, but still something is sneaking electron sips from the battery and we have its fingerprint. The next step is to isolate the circuit where the offender is hiding. A great way to do this is remove and reinsert underhood fuses one by one while monitoring the draw amperage. However, keep in mind, that while you do this, you will often wake up modules when you reinsert
the fuse. In which case, you will need to wait until such a module goes back to sleep before continuing to the next fuse. When you pull the right fuse, the draw will stop on the ammeter. In the case of this Explorer, it was a 60-amp fuse in the underhood fuse panel — fuse 1. See Photos 8 and 9.

When fuse 1 was pulled, the current dropped to zero. Looking at the fuse explanation chart (Photo 10) for the under hood fuse panel (panel number 1), shows fuse number 1 (1.1) to supply power for fuses 1, 2, 3 and 5 in the interior fuse panel (panel number 2).

Pulling these fuses one at a time in the interior fuse panel hit pay dirt when fuse 3 was removed, the current draw dropped to (nearly) zero once again. See Photo 11.

Looking at the fuse chart for the interior fuse panel found three suspects listed. See Photo 12.

The draw was proven to be in the direction of the audio unit (radio), amplifier or the DVD player (if equipped). The DVD player was quickly eliminated from the suspects list, due to the fact that this vehicle didn’t have one. The amplifier is behind the trim panel to the right of the cargo area. Not hard to get to, but the radio slides out of these easier. So, the radio was removed and unplugged to see if the draw went away. See Photo 13.

With the radio unplugged, the ammeter was inspected again for the results. The draw was still there. Only one suspect module left now. Time to go prove it.

With the amplifier disconnected (still shown as connected in Photo 14), the amperage dropped instantly.

The cause of this draw was that the amplifier was not going to sleep. A new amplifier fixed this vehicle. Let’s try another one.

This is a 2005 Ranger 3.0L. At first, battery draw was 0.34 amps. See Photo 15.

After only a few minutes, the draw dropped to the guilty item’s signature draw of 0.14 amps. See Photo 16.

Pulling underhood fuses found that the draw disappeared when fuse 5 (50A) was removed. See Photo 17.

The charts show that fuse to power the “Smart Junction Box” (SJB), which is the interior fuse panel. An SJB is not only a fuse panel, it is also a GEM module (BCM) combined into one unit. This 50A fuse may power a laundry list of items, and the underhood chart is not much help this time since it only says the SJB. So, it’s off to the power distribution charts to see what is powered by that fuse.

A quick look shows that fuses 17, 11 and 12 in the SJB are what that fuse powers. Fuse 17 is for the flasher, 11 is a power supply for the SJB’s logic circuitry and fuse 12 is for the subwoofer amplifier. The SJB was accessed by removing the passenger side kick panel. See Photo 18.

The removal and installation of the SJB’s fuse will awaken the supposedly sleeping module. So, the flasher fuse and the amplifier fuses were pulled. The draw remained. Pulling fuse 11 for the SJB’s logic circuitry dropped the ammeter to zero.

For this model, the SJB had to be programmed. Using the IDS, the configuration data was removed from the old module and loaded into the new module after its installation and the current draw problem was solved. I hope that you enjoyed the information, and have the opportunity to profit from it soon.


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