compression when do i

[bigmike35]

when do i check it(when its cold or when hot) if so why

[Nasher]

Checking compression is partly about getting near equal amounts on all cylinders to identify a dodgy one, as well as a general health check.

I've always done it cold but don't know whats recommended.

Anyway, Its easier to do cold as you don't burn your fingers on hot Spark Plugs and bits of engine.

Nasher

[Nos4r2]

Doesn't matter when you check it as long as you do them all at the same temperature-the important bit is that all readings are within max 15% of each other.

Fingers crossed Mike!

[rama]

should be done with engine hot. should realy open the throttle fully also and either stick a spark tester on the plug leads or disconect the coils.

[Nos4r2]

Originally Posted by rama

should be done with engine hot. should realy open the throttle fully also and either stick a spark tester on the plug leads or disconect the coils.

^^^ Ideally I'd agree, but Mike was having probems with #4 cylinder not firing so there's no way of being certain all 4 cylinders are at the same temp.

Spark tester and fully open throttle are essential-though you CAN do it by turning the engine over with ignition off by shorting across the starter solenoid on the engine in question.

[jwalker]

Originally Posted by bigmike35

when do i check it(when its cold or when hot) if so why

Hot is best because it is nearest to running conditions.

Remember to do it with all the spark plugs removed and the throttle wide open.

Edit: oops, a bit late.