Compression Test

[joe blo]

i just want to find out the process for doing a compression test. its on a rb25det

[Sheriff Wan]

- Disconnect your coil pack loom

- Remove spark plugs

- Screw the compression guage in the spark plug hole and turn the engine over for about 5 seconds

- Repeat the last step for all cylinders

Things to note:

Engine should be warm

[Jmaac]

Dry test, same as above but start the car first and pull the fuel pump/efi fuse, car should idle out

When cranking the car make sure your at WOT otherwise you'll need to crank it longer to get a stable reading

If no good, do a Wet test which is the same, but add a tablespoon of oil to each cylinder

Edited June 26, 2009 by Jmaac

[MrStabby]

Also, if any cylinders are down, squirt some oil in and re-try the test. If the compression goes up when using the oil, its rings, if it doesnt its valves or headgasket.

[joe blo]

do i have to take the fuse out for the fuel pump or anything?

[Beer Baron]

yes you should unless you want fuel spraying into the cylinders. take it out while the engine is idling so that the engine uses up whatever fuel is in the rail etc, otherwise when you do the test the injectors will open and release that fuel which is under pressure in the rail/lines/etc.

[joe blo]

do i do it with the throttle fully open also? i think ive read that somewhere

do i just take the fuse out thats in the boot of my r33?

Edited June 26, 2009 by joe blo

[JonnoHR31]

just unplug the injector loom, one of the 2 grey plugs at the front of the fuel rail

[blind_elk]

do i have to take the fuse out for the fuel pump or anything?

Just disconnect the CAS, so it can't signal the injectors to operate.

[Harry-Hotpants]

disconnect ur cas, therefore ur ecu doesnt get a signal to open injectors or fire coils, also hold throttle open whilst crankin or you will get low results. i literally just did one on mine yesterday