DIESEL TIMING CHAIN AND GEAR WEAR INSPECTION

VEHICLES AFFECTED: 1982-85 C, K, G, P 1, 2, 3 Series With 6.2L Diesel Engines ---------------------------------------

The timing chain on a 6.2L diesel engine has some slack or deflection. This can be up to 0.800 inch on a used engine. Timing chains that have worn or stretched, and have a deflection greater than 0.800 inch can cause an engine to experience rough idle, low power, poor fuel economy, and white smoke. Therefore, it is suggested that the timing chain deflection be checked whenever the front cover is removed from the engine. The following procedure is for checking the timing chain deflection.

Checking Procedure

1. Mount a dial indicator to the front of the block.

2. Position the dial indicator so that the plunger contacts the timing chain between the two gears.

3. Pull the chain outward (parallel to the front face of the block) the maximum amount with finger pressure on the inside of the chain.

4. Set the dial indicator to zero.

5. Move the chain inward (parallel to the front face of the block) the maximum amount with finger pressure on the outside of the chain.

6. The total indicator travel can be noted. On a used engine the deflection must not exceed 0.800 inch. If the deflection exceeds this limit, the gears and timing chain must be examined for wear and replaced as necessary. With new parts the maximum deflection must not exceed 0.500 inch.

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.