Troubleshooting > GM Diesel
|In order to do proper diagnostics you will need a scan tool and some special tools such as a vacuum test gauge J44638 available from GM Special Tools http://gmspecialservicetools.spx.com/ . Also note that 1 Mpa (megapascal) is equal to approximately 145 PSI.High Pressure Common Rail Basic Information
The high pressure pump builds rail pressure and delivers it to the fuel rail manifold where it flows through the injector lines to the injectors. The fuel pressure regulator in the high pressure pump controls rail pressure. The injectors have a hollow check ball that holds high pressure fuel until the fuel solenoid is actuated by the ECM, this allows the check ball to rise off its’ seat and an injection to take place. If the check ball in the injector is leaking due to erosion on the seat or the high pressure limit valve leaks then it will not build enough rail pressure to start. It takes approximately 2500 PSI 2500 PSI rail pressure to start.
No Start or Hard Start
Surge at idle
White-Blue smoke at idle when cold
Fuel Supply and Fuel Filter Housing
High Pressure Pump (CP3 Pump)
Use the following information regarding diagnostic trouble codes in addition to the normal diagnostic procedures outlined in the service manual or technical service bulletins.
DTC P0087; fuel rail pressure less than 22.5 MPa at more than 600 RPM, fuel rail pressure too low.
DTC P0093 on 2001, P1093 on later vehicles; Difference between commanded fuel pressure and actual pressure is greater than 20 Mpa.
DTC P0201 – P0208 misfire codes
DTC P2146 or 2149; cylinder bank shut down
|To properly diagnose a 6.5 L vehicle with the DS injection pump you will need a scan tool. The 1994 and 1995 are OBD1 and the 1996 through the 2000 model year is OBD2, so the diagnostic codes are different depending on the year range.LOW POWER
1. Low or no fuel supply pump pressure
2. Dirty fuel filter
3. Wastegate control solenoid
HARD START HOT
NO START, DIES INTERMITTENTLY OR STALLING
We use the following guidelines to determine if a PMD may need to be replaced, this is a simple first step and is less in depth than the GM bulletin noted below.
If the problem you are experiencing doesn’t correspond with the problems noted above then follow the trouble shooting below to help pinpoint a possible bad PMD. (GM Bulletin #77-63-06A)
1. Check fuel system for air (check at fuel return from pump), supply pump pressure, and fuel filter condition.
2. Check the PCM and injection pump wiring harness for chaffing and/or loose terminals at the PCM connector, the 15 pin connector and the PMD connector. See the WIRE HARNESS CONNECTIONS section for more information.
3. Check all engine and vehicle harness grounds.
4. Check for loss of ignition voltage on terminal “D” at the fuel solenoid driver connection to the injection pump. Refer to ENGINE CONTROLS IN THE 1998 SERVICE MANUAL FOR ALL MODEL YEARS.
5. Verify that the condition is still present:
6. For active DTC’s 35 or P1216, refer to Engine Controls in the 1998 Service Manual for all model years. If the DTC diagnostic table flow chart directs you to replace the injection pump, replace the PMD (Pump Mounted Driver) which is also called the Fuel Solenoid Driver. Go to step 9.
7. For stall condition, disconnect the Optical Sensor (Encoder Sensor) and operate the engine in back up mode (you will experience an extended crank time during starting, up to 15 seconds). A bad noise suppression harness or no noise suppression harness can also cause a stalling condition. If the condition is still present replace the PMD only. Go to step 9.
8. For a no start condition, check injection pulse width (94-95) or C-Time (96-2000 Fuel Solenoid Closure Time) with a scan tool, while cranking (maintain minimum cranking speed 100 rpm cold and 200 rpm hot). If C-Time is 1.95ms (94-95) or 0.01ms (96-2000) replace the PMD. Go to step 9.
9. Replacing the PMD (Fuel Solenoid Driver):
Removing the PMD requires a T15 TORX bit. Replace the heat transfer pad and use snap ring pliers to remove the calibration resistor. Install the calibration resistor into the new PMD.
If the calibration resistor is damaged, there is an identification number on it (1 through 9) and we have them available.
IMPORTANT: IF THE PMD CALIBRATION RESISTOR IS MISSING, DTC 56 (1994 1995) OR P1218 (1996-1998) WILL SET.
INSTALL PMD: Align the mounting screws on the PMD with the holes on the injection pump (or on the remote mount PMD heat sink) Torque the mounting screws to 23 LB-IN.
IMPORTANT: DO NOT INSTALL THE FUEL SOLENOID DRIVER WITHOUT A NEW HEAT TRANSFER PAD. DO NOT REUSE A HEAT TRANSFER PAD. USE A NEW HEAT TRANSFER PAD ONLY. THE HEAT TRANSFER PAD IS REQUIRED TO PREVENT RAPID FAILURE OF THE FUEL SOLENOID DRIVER FROM OVERHEATING.
NOTICE: DO NOT OVER TIGHTEN FUEL SOLENOID DRIVER MOUNTING SCREWS. DAMAGE TO THE FUEL SOLENOID DRIVER WILL RESULT.
For Other Starting Issues, Check the high resolution signal, cam signal (from the injection pump) and crank signal.
X = good signal, 0 = no signal
Hertz Readings (HZ) while cranking and at idle
FUEL SUPPLY PUMP
PMD (pump mounted driver)
TDC OFFSET LEARN
WASTEGATE CONTROL SOLENOID
WIRE HARNESS TESTING
DTC17 (P0370) high resolution circuit fault can be caused by aeration in the fuel from a plugged fuel filter or low fuel supply pump pressure.
DTC18 (P0251) Pump cam reference error
DTC19 (P0335) crankshaft position reference error
DTC34 (P0216) injection timing stepper motor, watch the stepper motor and make sure it retracts when activating TDC learn.
DTC35 (P1216) fuel solenoid response time too short, less than 1.2 ms or less than .75ms on later years.
DTC36 (P1217) fuel solenoid response time too long, more that 2.5 ms, can be caused by a weak fuel control solenoid.
DTC56 (P1218) injection pump calibration resistor error. Usually is caused by a missing resistor, and this codes sometimes only sets after attempting TDC offset learn.
DTC78 (P0236) turbo boost performance, this is usually caused by a bad wastegate control solenoid or low vacuum.
DTC84 (P1125) APP can set if foot is on throttle and brake when key is turned on.
DTC88 (P1214) TDC offset error, the pump to engine timing must be within plus/minus 2 or 2.5 degrees when doing TDC offset learn or this code will set. This code could also set if the starter was used to crank the engine over while installing the injection pump, this will sometimes partially shear the crankshaft timing chain gear key.
|Hard Start Hot (after sitting 10 minutes to 2 hours)
1. 6.2L and 6.5L engines need a minimum of 200rpm hot cranking speed (the fan should be a blur). If cranking speed is too slow, they are hard to start (between 120° – 180° coolant temperature) hot, but start fine cold. Check battery connections, batteries, cables and starters. Fix a slow cranking problem first, then if it still starts hard, it could be a problem with the injection pump.Surges, Runs Rough
1. Check fuel supply pump pressure, it should be about 5-6 PSI on the mechanical supply pump or 4-5 PSI on the electric fuel supply pump. 2. Check for air; use a clear line on the return fitting of the injection pump and look for air. If you have air coming out of the return line then install a clear line before the supply pump.