Compression test

[fmster]

O.K Folks What is the proper way to do a compression test?

 

[notacarlo]

Get a compression test kit and screw it into #1 and rotate motor to TDC...note peak psi at tdc and hold there to see if she leaks down. Follow suit on each cylinder.

 

[chopped39]

There are different ways to do a compresion test. you can do it with it running with schader valve removed or disabling fuel and spark and crank it over three times and watch for highest psi. some people leave the other spark plugs in the proper way is to pull them all. Or you can use a scope with high amp probe with a sync trigger and perform cranking compression test. the most accurate way is using a in cylinder pressure transducer and a lab scobe. If you are doing a leakdown test pull plugs and rocker shafts set piston at top dead center and install leakdown tester and follow instructions on tester. I do the leakdown with the piston at tdc and at bdc. bdc will hwlp if the cylinder wall has crack at middle of cylinder. I had one that had coolant in crank case that someone just put headgaskets on . During leakdown at tdc there was nothing all cylinders had 10% leakage . I performed leakdown at bdc and when testing #3 coolant blew into overflow. pulled engine and sure as sh!t it had a cracked cylinderwall. Sorry for rambling on:biggrin: hope this helps

 

[pacecarta]

Get a compression test kit and screw it into #1 and rotate motor to TDC...note peak psi at tdc and hold there to see if she leaks down. Follow suit on each cylinder.

what your discribing is sounds like a leakdown test but your incorrect there as well a leakdown requires a compressor
, op asked about compression test, two completely different things
you cant do a leakdown with a compression tester


warm engine , charge battery (i like to put it on a bat charger/starter and leave it connected)
remove plugs
prop open throttle body (dont forget to remove when you're done)
unplug the ignition module
screw in the tester and crank three to four times , watch the first hit
record the reading and repeat test for all cylinders
if they vary more than 20% from high to lowest you have an issue
the leakdown tester can be used to determine more about a cylinder that shows an issue but if the cylinder is very low theres probably more than just a bad ring so tear down will be unavoidable and youll get to see the heads ,the pistons and the gasket to determine why