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Home >> GMC >> 2001 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 6.5L (L65) (Introduction) >> Repair Instructions >> Fuel Injection Pump Timing Adjustment

Fuel Injection Pump Timing Adjustment

Tools Required

This procedure should be used after an injection pump installation or when injection timing needs to be checked or adjusted. A scan tool must be used to check or adjust injection timing. A static timing mark can be used as a reference. If a static timing mark is not present on the injection pump mounting flange, one can be scribed to further assist in how far the injection pump needs to be rotated.

Injection Pump Timing Specification:  All injection pump timing averages 3.5 degrees.

IMPORTANT: There will be no change in engine performance or vehicle driveability if injection timing is advanced during the Time Set procedure. The injection timing must be set to Injection Timing Specifications. If the injection timing is not set correctly, a possible DTC P0216 may set (see DTC P0216, Conditions for setting the DTC).
  1. Start the engine.
  2. Run the engine to operating temperature.
  3. Install a scan tool.
  4. Use a scan tool to activate Time Set (if Time Set has been activated correctly, Des. Inj. Time on the scan tool will read 0.0 degrees).
    IMPORTANT: The Actual Injection Time value on the scan tool will fluctuate. The average reading should be 3.5 degrees.
  5. The Actual Injection Time (scan tool display) should be approximately 3.5 degrees. If not, continue to step 6.
    IMPORTANT: If the engine stalls during Time Set activation, slightly (1 mm equals 2 degrees) rotate the injection pump toward the driver side of the vehicle, tighten flange nuts and repeat Time Set.
  6. If the injection timing needs to be adjusted, continue. If not, the adjustment is complete.
    7. IMPORTANT: Move the A/C compressor to the side to improve access to the injection pump lower mounting bolts.
    Fig 1: Left Hand Injection Pump Flange Nut & J 41089
    GM707578Courtesy of GENERAL MOTORS CORP.
  7. With the engine OFF, use the J 41089  in order to loosen the left hand injection pump flange nut. See Special Tools .
    8. Fig 2: Right Hand Injection Pump Flange Nut & J 41089
    GM706303Courtesy of GENERAL MOTORS CORP.
  8. With the engine OFF, use the J 41089  in order to loosen the right hand injection pump flange nut. See Special Tools .
  9. With the engine OFF, use the J 41089  in order to loosen the center top injection pump flange nut. See Special Tools .
  10. Use the J 29872-A  in order to slightly rotate the injection pump. See Special Tools .
  11. Set the Actual Injection Time to 3.5 degrees.
    IMPORTANT: It is normal for the Actual Injection Time value on the scan tool to fluctuate. The average fluctuation of Act. Inj. Time should be 3.5 degrees. If the Act. Inj time is below 3.5 degrees, SLIGHTLY (1 mm equals 2 degrees) rotate the injection pump toward the driver's side of the vehicle. If the Act. Inj Time is above 3.5 degrees SLIGHTLY (1 mm equals 2 degrees) rotate the injection pump toward the passenger side of the vehicle.
  12. Continue to repeat the procedure until average fluctuation of the Actual Injection time is 3.5 degrees.
    • If the actual injection time is above 3.5 degrees, slightly (1 mm equals 2 degrees) rotate the injection pump towards the passenger side of the vehicle.
    • If the actual injection time is below 3.5 degrees, slightly (1 mm equals 2 degrees) rotate the injection pump toward the driver side of the vehicle.
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