Things You'll Need:
- 0-50 engine compression gauge
- End fitting matching spark plug size
- 1/2-inch drive spark plug socket
- 1/2-inch drive extension
- 1/2-inch drive ratchet
- Fender cover
- Service manual for the year model of the vehicle
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Step 1
Identify the year model of the vehicle and purchase the service manual that includes the procedure. Sometimes this procedure is not available in a general service manual and must be located by your mechanic via computer.
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Step 2
Identify the size of the spark plugs. Attach the matching 1/2-inch drive spark plug socket to the 1/2-inch drive extension. (The extension should be long enough to bring the ratchet level with the top of the engine). Attach the extension to the 1/2-inch drive ratchet and push the on/off lever on the ratchet to the off position. (Counterclockwise).
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Step 3
Position fender cover over the fender side you are starting on.
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Step 4
Look up the firing order for the engine you are working on and remove the first spark plug in that order using your 1/2-inch drive set-up. Look for carbon build-up on each spark plug. This is a symptom of a blow-by condition.
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Step 5
Disconnect the battery and all spark plug wires
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Step 6
Attach the appropriate size fitting to the compression gauge, and screw it clockwise into the spark plug hole until hand tight.
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Step 7
Have a helper turn over the engine while you are observing the compression gauge reading. You are looking for a steady rise from 0 to the maximum compression for the engine. If the pressure does not hold at a steady position, there is blow-by (loss of cylinder compression) in this cylinder.
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Step 8
Repeat this procedure at every cylinder, and note all cylinders that are not maintaining steady pressure. These cylinders will require a complicated procedure to be repaired before the vehicle is returned to acceptable running condition.
