UPDATE COMPRESSION CHECK (REVISED PROCEDURE)

Model and Year: 1989 M CAR

This bulletin cancels and supersedes the "COMPRESSION CHECK" procedure found on page 6-13 in the 1989 GEO Service Manual.

COMPRESSION CHECK

Figures 4 and 5

Check the compression on all three cylinders as follows:

1. Warm up engine.

2. Stop engine after warm up.

3. Remove all spark plugs and disconnect distributor wire harness at connector.

4. Remove 15A fuse for main relay (Figure 4).

5. Install compression gage into spark plug hole.

6. Disengage the clutch (to lighten starting load on engine), and depress the accelerator pedal completely to make the throttle full-open.

7. Crank the engine with the battery fully charged, and read the highest pressure on the compression gage.

8. Carry out steps 5 through 7 on each cylinder to obtain three readings.

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.