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Compression test your engine

Filed Under (Diagnostics) by ghost_22_47 on 20-10-2011

Tagged Under : , , ,

This is an instruction on how to perform a compression test on an engine.

I will be using this motor, an S13 Red Top SR20DET.

Red top SR20DET

Here is what I will be using to perform the test.

This is a Compression and Vacuum test kit

Matco Compression and Vacuum test kit

Step 1) You will need to warm the engine up to operating temperature

Step 2) Shut Engine off

Step 3) Begin by disconnecting the coil pack connectors

Coil Pack Connectors Unplugged

Step 4) Remove the Coil Packs or Spark plug wires

Coil Packs Removed

Step 5) Remove All Spark Plugs

You should remove all of the spark plugs because having only one out and the rest in creates a resistance because of the pressure in the cylinders that have plugs, this can slightly throw off your readings.
Not to mention you can go very easily and quickly between cylinders.

All Spark Plugs Removed

 Step 6) Remove Fuel Pump Fuse

Remove the Fuel Pump Fuse

Step 7) Disconnect Fuel Injector Connectors

The reason is that even though you took the fuel pump fuse out, the Injectors will still pulse and spray whatever fuel in the system into the cylinders and wash them out.

Injector Connector Removal

 Step 8) Screw the compression extention adaptor into the spark plug hole

Compression Test Adaptor

 Step 9) Connect your compression gauge up to the adaptor

Compression Gauge Connected

Step 10) Have someone crank the engine 8-10 pulses or until the gauge has stopped at it’s compression number.

I had 150PSI in the front 2 cylinders and 145PSI in the last 2, which passed specs.


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