Compression test - How too?

[Wobba]

Can I get a brief guide on doing my own compression test with a compression tester? Going to buy one tonight and do it.

[MAXIBOY]

remove plugs..
screw tester in a cylinder.
hold throttle wide open and crank engine over for a few turns.
do all cylinders..
then add a few drops of oil and redo any cylinders that are low.
see if the readings increase.
most important is all cylinders are very close.
then the figures.

should tell you a few things..if all are fine and close engines ok.
all low but similar engines worn. if a rise once retested with oil added rings more than likely worn. if not valve seat might need work..if only one or two cylinders low could be a head gasket single valve damage etc

at this point a cylinder leakage test become invaluable..

[Wobba]

Thanks mate. Do I unplug the fuel pump? Dont want to flood it!

Will this fit?

http://www.halfords.com/webapp/wcs/s...egoryId_165557

[MAXIBOY]

no as it will alter the compression ratio..will just crank out..won't flood it as the plugs aren't in it.

should be fine.

[Wobba]

When you say plugs you mean spark plugs or injectors. Surely, if injector plugs are in the powered they will shoot fuel in them and flood it eventually?

Sorry, I may be being a bit of a newbie today as my brain has seized.

[MAXIBOY]

leave the injectors alone remove the spark plugs..

flooding occurs when the spark plugs get flooded by fuel..can't happen if there removed..

[Brealbags]

yes disconnect the injectors in some way!!!

Either remove fuel pump fuze or relay or disconnect injector wiring. First de pressureize the fuel system by trying to run the car with no fuel pump relay in

Damage to cat

[MAXIBOY]

i never do..running a few cylinders of unburnt fuel will not damage the cat..

i do cover the remaining plug holes to stop fuel getting every where though.

never had a problem with this method been doing it oner 20 years now..

[Brealbags]

fair enough just telling how it should be done to the book. Make sure throttle is wide open though when your cranking the engine so it can take in as much air as poss.

Your looking at the difference in readings accross the cylinders rather than trying to get to a setpoint reading.

[Wobba]

I was going to say, covering the holes may be wise hehe. Also, would it be safer to remove the king lead from dizzy or is the spark from the HT leads safe without the plugs in to just dangle about...