How To Do A Compression Test... - Honda Prelude Forum

atlxchink · 10-30-2001, 12:50 AM

Asking for a friend. He has the tool. Can you give step by step instructions? thanks
SAM

TimeRacer · 10-30-2001, 01:10 AM

C-Speed racing has a nice how-to page...

http://www.c-speedracing.com/howto.html

Take a look, it's not all that hard to do, just make sure that you pull the right fuse for the fuel pump.

Might as well do it on your car too.

~Doug

EviLPenEviL · 10-30-2001, 06:34 PM

What is the compression test suppose to do neways??

I'm a lil bit illerate on this type of stuff....

latez....

71dsp · 10-30-2001, 06:41 PM

It is a diagnostic tool to help you determine if a cylinder leaks some; i.e. doesn't make full compression, which affects power.

A leakdown test will tell you a bit more about the condition of the engine, though.

1. pull the fuel pump fuse
2. pull the coil spark wire
3. pull the spark plug on the cylinder you're going to test
4. attach the compression tester
5. crank the car over and see what compression it's making

Kool-Lude · 10-30-2001, 06:52 PM

Quote:

Originally posted by 71dsp
A leakdown test will tell you a bit more about the condition of the engine, though.

How is this done? (you've probably said it before..i'll do a search)

Quote:

Originally posted by 71dsp
3. pull the spark plug on the cylinder you're going to test

Why does that site instruct to pull ALL the plugs before testing?

71dsp · 10-30-2001, 07:02 PM

Quote:

Originally posted by Kool-Lude
How is this done? (you've probably said it before..i'll do a search)
Why does that site instruct to pull ALL the plugs before testing?

There is some debate as to whether you should pull all the plugs or just the one you're testing. I say pull the one your testing and leave the others so that there is an equal load on all the cylinders.

To do a leakdown test, you need a leakdown tester (duh) and an aircompressor.

1. Set the piston that you are testing to TDC
2. Remove the plug on the cylinder you're testing
3. turn on the air compressor and set it for 110 PSI
4. hook the leakdown tester to the air compressor
5. hook the leakdown tester to the engine
6. SLOWLY turn the regulator on the leakdown tester until the supply pressure is 100 PSI
7. read the piston pressure; if you get 99 PSI, you have 1% leakage, 98 PSI, 2% leakage, etc.

Production engines can have up to 5% leakage. Anything over 10% means that something is wrong.

You can listen for where the air is escaping to further figure out where a problem might be.

Air coming out of tailpipe -> leaking exhaust valve(s)
Air coming out of intake -> leaking intake valve(s)
Air coming out of oil fill hole -> leaking cylinder rings

MAKE SURE THE CYLINDER IS AT TDC!!! IF YOU RUN 100 PSI THROUGH A CYLINDER THAT'S NOT AT TDC, THE ENGINE WILL SPIN, AND SPIN WITH ENOUGH FORCE TO HURT SOMEONE.

Kool-Lude · 10-30-2001, 07:17 PM

So would you adjust the valves before a leak down test in order to avoid chasing down an intake/exhaust leak that is caused from valves being out of specs?

71dsp · 10-30-2001, 07:42 PM

Doesn't matter. When the piston is at TDC, the valves should be fully shut. If the valve rocker is so far out of adjustment that the valve is open, you have bigger problems! Chances are, if that's the case, the cam and the valve rocker will be toast. When the piston is at TDC, the cam lobe will be on the opposite side of the cam from the rocker (i.e. the cam shouldn't even be touching the valve rocker at that point).

Oh, I forgot to add something, when I say, TDC, I mean, TDC on the compression stroke.

SADWAP97 · 10-30-2001, 08:15 PM

i did a compression check a few days ago and i had a reading of about 200psi on each cylinder. is that too high or is that good?
or it doesn't matter as long as there isn't a large range between each cylinder?