DIESEL FUEL SYSTEM CHART DIAGNOSTIC CHECKLIST

VEHICLES AFFECTED: All 1982-1984 Models With A 6.2L Diesel Engine

The following checklist and diagnostic chirts are provided as an aid to technicians for servicing the 6.2L diesel engine. Before removing the fuel injection pump from the engine, the Automotive Diesel Diagnostic Checklist should be completed. A copy of the checklist should accompany the pump when sent for repairs.

TIMING METERS

Diesel engine timing meters have the capability of checking engine timing and rpm. These meters can be used to perform diagnostic checks on the 6.2 liter diesel engine. The 6.2 liter engine's injection pump timing must be set to static specifications outlined in the Service Manual or appropriate Truck Service Bulletin.

TIMING METERS AND DIAGNOSTIC PROCEDURES

The timing meter's timing capability and tachometer can be used to check the injection pump's housing pressure cold advance and rocker arm mechanical light load advance functions for operation. These checks may indicate if the pump's advance solenoid, advance piston assembly and cam ring are functioning and not binding or seized.

PROCEDURE

1. Place the transmission selector in park, (neutral with manual transmission) apply the parking brake and block the wheels.

2. Start the engine and let idle until fully warmed up. Then shut off engine.

3. Clean any dirt from the engine probe holder (rpm counter) and crankshaft balancer rim.

4. Attach the timing meter, following manufacturer's instructions.

5. Start engine and adjust idle to 650 rpm. Note engine timing and rpm readings.

HOUSING PRESSURE COLD ADVANCE CHECK

Disconnect advance solenoid's terminal wire at the injection pump. Attach a jumper wire to the battery positive terminal and touch injection pump's advance solenoid terminal. Note engine timing and rpm readings.

When the advance is functioning properly, the engine's timing will advance approximately 3 to 5 degrees and rpm will increase when the solenoid is energized.

ROCKER ARM MECHANICAL LIGHT LOAD ADVANCE CHECK (FIGURE 1)

Using a ten-inch long screwdriver, push the injection pump's rocker arm (at lower end) towards injection pump. Note engine timing and rpm readings.

When the rocker arm mechanical light load advance is functioning properly, the engine's timing will retard approximately 3 to 5 degrees and rpm will decrease.

Injection pump removal is normally required to repair the pump's internal mechanical advance.

Engine rpm may require readjustment to emission label specifications when diagnostic procedures are completed.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.