Toyota Celica/Supra 1971-1985 Repair Guide

Checking Engine Compression


See Figure 1

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Fig. Fig. 1: A screw-in type compression gauge is more accurate and easier to use without an assistant

A noticeable lack of engine power, excessive oil consumption and/or poor fuel mileage measured over an extended period are all indications of internal engine wear. Worn pistons rings, scored and worn cylinder bores, blown head gaskets, sticking or burnt valves and worn valve seats are all possible culprits here. A check of each cylinder's compression will help you locate the problems.

As mentioned in the Tools and Equipment section of General Information & Maintenance , a screw-in compression gauge is more accurate than the type you simply hold against the spark plug hole, although it takes slightly longer to use (it's worth it). To check compression:

  1. Warm the engine up to operating temperature.
  3. Remove all four or all six spark plugs.
  5. Disconnect the high tension wire from the ignition coil.
  7. Screw the compression gauge into the No. 1 spark plug