Engine Controls - Adjustments - 6.5l Diesel GMC Suburban I

ENGINE MECHANICAL

Note. The Assembly Line Data Link (ALDL) connector may also be referred to as the Data Link Connector (DLC). The SERVICE ENGINE SOON (SES) light may also be referred to as the Malfunction Indicator Light (MIL).

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. 6.5L uses hydraulic lifters. No adjustments are required.

CHECKING/ADJUSTING INJECTION TIMING

Original factory injection pump timing is marked with a static timing mark, a line scribed across both the pump mounting flange and the front cover. This static timing mark should be used as a reference. If timing mark is not present on mounting flange, scribe a line to assist in how far injection pump needs to be rotated.

1. Start and warm engine to normal operating temperature. Connect Tech 1 scan tester. Set scan tester to OUTPUT TEST/INJ PUMP mode. Activate TDC TIME SET. The DESIRED INJ TIM value will read zero. NOTE: If engine stalls when TDC TIME SET is activated, turn engine off. Loosen injection pump nuts. Slightly rotate injection pump toward driver's side of vehicle. Tighten injection pump nuts. Repeat step 1).
2. Ensure engine is running, then check "MEASURED INJ TIM" for proper timing specification. See «INJECTION PUMP TIMING»(/gmc/suburban/i-1992-1999/remont/adjustments/#engine-controls-adjustments-65l-diesel) below. If timing needs adjustment, turn engine off to avoid engine damage, then adjust injection pump. A 1-mm pump movement equals about 2 degrees timing.

INJECTION PUMP TIMING (DEGREES BTDC @ RPM)

TDC OFFSET LEARN PROCEDURE

Note. It takes PCM 20 seconds to learn TDC offset.

This procedure is only used when one of following conditions exists

1. Front cover and PCM are removed and replaced at same time.
2. Injection pump and PCM are removed and replaced at same time.
3. Front cover and/or crank sensor, pump and PCM are removed and replaced at same time.
4. Front cover has been removed.
5. Engine has been replaced.

1. Start and warm engine to normal operating temperature. Connect Tech 1 scan tester. Using scan tester, select OUTPUT TEST or INJECTION PUMP mode, and activate TDC OFFSET LEARN. NOTE: If engine stalls when "TDC TIME SET" is activated, turn engine off, then slightly rotate injection pump toward driver's side of vehicle. Tighten mounting nuts and repeat step 1).
2. If learned TDC OFFSET reading is between .00 and -.50 degrees, procedure is complete. If reading is not as specified, slightly rotate injection pump and repeat step 1). A 1-mm pump movement equals about 2 degrees timing.
3. To achieve a negative reading, rotate pump toward driver's side. To achieve a positive reading, rotate pump toward passenger's side.

IDLE SPEED

Idle speed is not adjustable. PCM controls all fuel delivery/modes based on inputs from AAP, ECT and BARO sensors. System is equipped with an electronic fuel injection pump.

THROTTLE POSITION (TP) SENSOR

Throttle control is electronic with NO mechanical link from engine to accelerator pedal. The PCM monitors the position of accelerator pedal based on signals from a non-adjustable Accelerator Pedal Position (APP) module. The APP is mounted above the accelerator pedal.

See also:
• INJECTION PUMP TIMING