48-PIECE SAE AND METRIC THREAD RESTORER KIT

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Addressing GDI Issues

• PROPERLY REPAIR OR RENEW DAMAGED THREADS

• FRACTIONAL AND METRIC

• THIS SET IS EQUIPPED WITH AN ENTIRE 48-PIECE TOOLING SELECTION TO SIMPLIFY ALL RETHREADING JOBS

• RETHREADING TAPS AND DIES ARE HIGHLY TEMPERED FOR STRENGTH AND DURABILITY have seen this code on a GDI engine it was due to an injector leaking fuel from carbon build-up in the pintle and pintle seat area. Normally this can be confirmed by monitoring the fuel pressure bleed-off during a key off condition.

All GDI engines are designed to maintain key-off fuel pressure for at least five minutes. You should also be aware that a fuel pressure bleed-off can be caused by a faulty high pressure pump. Don’t forget to always check the oil level.

For those of you who have a four-gas infrared unit, removing the spark plugs and sniffing out the combustion chamber of each cylinder would be a good test. Elevated hydrocarbons would pinpoint the leaking injector as well as a wet spark plug.

Let’s take a look at a case study from a P219A code. This is a case where a judgement call needs to be made. Using the scan tool, we conducted a fuel pressure drop test in Fig. 7. Notice two injectors indicated 68 PSI. We notified the car owner that the first step was to try chemically cleaning the injectors through the injector rail. You cannot guarantee this would be the fix. The alternate fix would be more expensive, involving replacing the injectors. Now let’s look at the scan tool reading after we chemically cleaned the injectors in Fig. 8. Did you notice the good test results?

The Honda V-6 fold. This module contains the capacitors that charge all the injectors with 65 volts. As in all GDI engines, the injectors are sequentially ground-side controlled by the PCM. On the V-6 Honda engines the PCM will send a TTL (transistor to transistor) signal to the FICM module to control each injector on time.

We recently had a tech call from another shop with a Honda Pilot with a P219A code. The technician made a mistake by replacing the FICM module. We advised him to scope the TTL on-times from the PCM to the FICM. The TTL on-times for bank 1 indicated 0.4 milliseconds while bank 2 indicated 0.8 milliseconds. This tells us the PCM was trying to lean out the injectors on bank 1. The cause was a leaking injector on bank 1.

The high pressure fuel pump again is mechanically driven by the camshaft and electronically controlled by the PCM.

Fig. 9 shows a lab scope voltage waveform and an amperage waveform. Some high pressure pumps are ground side controlled by the PCM while others are feed side controlled by the PCM. The clue here is that by using a current probe we could clamp around any one of the two wires to obtain an amperage waveform. The resistance value of control solenoid is very low in the range of 0.5 ohms. The PCM will control this solenoid with an on/off frequency signal at about 4,000 hertz to limit the current flow values.

A good amperage waveform will only verify a good control circuit and will not help in verifying the mechanical integrity of the high pressure pump.

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Fig. 10 shows a cutaway of the high pressure pump, the control solenoid, the cam follower and the threelobe camshaft on a GM Ecotech engine.

A picture of a GDI injector is shown in Fig. 11. The compression seal at the bottom must be replaced if the injector has been removed. A seal installer is indicated in Fig. 12. The compression seal must be installed dry. The OTC tool kit includes an injector puller, an injector bore brush and an injector seal installer.

When monitoring fuel pressures on these engines, the scan tool may not show you the fuel pressure values in the King’s language. A conversion chart is indicated in Fig. 13, using a multiplier to convert a bar value or a MPA value to PSI.

As we stated earlier, the GDI injectors are capacitively charged with 65 volts and are ground side controlled by the PCM or the FICM module on the Honda V-6 engines. Noid lights and test lights will not work to determine if an injector drive signal exists when faced with a no-start. If doing a voltage trace with a DSO, you must use two channels of the DSO (one channel on each injector wire). Access to the injectors is not possible because they are buried. The easy access point would be at the harness or at the PCM. The two injector wires are wound around each other to counter the opposing magnetic fields. An injector pattern is indicated in Fig. 14. The blue indicates the injector was charged with 65 volts. The red trace indicates the injector was ground side controlled.

The yellow trace indicates a 10 amp value when the PCM supplied the ground. Moving to the right you can see the injector was again charged with 65 volts but the PCM did not supply the ground. You can see the yellow amperage trace did not indicate any current flow since the injector was not supplied with a ground by the PCM. It’s easy to see that using a current probe to check for an injector drive signal would be the preferred way. The current probe could be clamped around either of the two wires of the injector circuit. When an air fuel ratio code exists or a fuel pressure code exists, it can be beneficial to always note the freeze frame data for fuel pressure values. Fig. 15 indicates good fuel pressure values from our case study regarding the P219A code. Additional freeze frame values are indicated in Fig. 16. Note the PCM detected the first failure 217 miles ago while the last failure occurred 252 miles ago. In addition, note that there have been two failures since the first.

Now take a look at a good test drive on a V-6 Ford during a WOT acceleration in Fig. 17. Notice that the high pressure exceeded 2,100 PSI and the desired high pressured fuel was a near match.

Some manufacturers such as GM allow us to take charge of the command from the PCM to the fuel pump control module. In the example in Fig. 18 we increased the duty cycle command from the PCM to 37% and you can see the increase on the low side fuel pressure to 57 PSI.

For those who know the diagnostic value of current ramping conventional fuel pumps, be aware that the modern day fuel pumps are not supplied with constant voltage source, so the amperage waveforms will look different than that of the conventional fuel pumps.

And, the current flow values during idle no load conditions will be close to 3.5 amps. See Fig. 19.

In Fig. 20 notice that during an acceleration condition the current to the fuel pump peaked at nearly 8 amps. You can actually see the engine load conditions change during transmission shift points. This verifies how tight these systems are. The fuel pressure on the low side remained constant.

A GM vehicle with the 2.0 Ecotec engine came in with a MIL and two codes: P0087, and an additional code of P0089. See Fig. 21. It’s important to note these two codes are performance codes. They are not a circuit type code or a plausibility code. Using our scan tool we must first confirm that the low pressure side is performing properly. With that established, we now focus on the actual high side pressure and the desired high side pressures. Notice the scan data capture in Fig. 22. The bottom trace indicates the PCM is ramping up the duty cycle command signal to the high pressure pump control solenoid. The desired high side pressure was 2,175 PSI while the actual high side pressure indicated 50.8 PSI. The loss of power complaint was because the engine was running on low side fuel pressure only. Fig. 23 shows a picture of the old and new pumps. You can see the difference.

A Ford EcoBoost came in with a MIL with a DTC P0088 (fuel pressure too high). See Fig. 24. This is also a performance code. Fig. 25 shows the scan tool PIDs we selected. Fig. 26 is a scan tool capture before the symptom occurred. Now notice Fig. 27 where the APP values decreased during decel. Notice the actual fuel pressure remained high while the desired fuel pressure decreased. These examples show the value of scan data captured in the graphic mode.

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Bill Fulton is the author of Mitchell 1’s Advanced Engine Performance Diagnostics and Advanced Engine Diagnostics manuals. He is also the author of several lab scope and drivability manuals such as Ford, Toyota, GM and Chrysler OBD-I and OBD-II systems, fuel system testing, and many other training manuals in addition to his own 101 Lab Scope Testing Tips. He is a certified Master Technician with more than 30 years of training and R&D experience. He was rated in the top three nationally on Motor Service magazine’s Top Technical Trainer Award and has instructed for Mitchell 1, Precision Tune, OTC, O’Reilly Auto Parts, BWD, JD Byrider, Snap-on Vetronix and Standard Ignition programs. You may have also seen Fulton in many Lightning Bolt Training videos and DVDs and read his articles in many auto service magazines. He owns and operates Ohio Automotive Technology, which is an automotive repair and research development center and where the images for this article were produced.