DIY : Compression testies :)

Its that time of the month again....DIY JOBBY !


Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!


Aim: To test the compression of a engine - that is , basically see the internal condition of piston rings , valves , valve seals etc. Handy when purchasing a second hand car or if you are just paranoid like myself :D




http://www.ozhonda.com/gallery/water...2/7921-med.jpg



Required: Car. atleast 2 hands - only one foot is needed though. Compression tester tool , and spark plug remover.



Steps:


http://www.ozhonda.com/gallery/water...9naked-med.jpg


1. Open bonnet. Pull out all spark leads , then use removing tool to take out all 4 spark plugs.



2. Open fuse box in engine bay ( upper should be right corner) - take out the fuse marked ECU ( 15a i think ?) ( to disable the fuel and ignition)


http://www.ozhonda.com/gallery/water...2/7911-med.jpg

3. Place the compression tester tool into the 1st cylinder (any is ok) and tighten up. Either get a friend to hold it and read the reading OR leave it atop the engine bay. YOU MUST FOLLOW ALL STEPS IN THIS PHOTO....



http://www.ozhonda.com/gallery/water...2/7931-med.jpg

4. Jump into the cabin , apply WOT ( wide open throttle/ full throttle) and turn over the engine 6 times. Jump out , and read the top reading OR get ur associate to tell you the maximum psi reached. Record down and write the cylinder number/location.



5. Simply repeat for each cylinder - once all recorded pack up in the opposite fashion , reinsert sparkplugs + leads, then reinstall the ECU fuse and away you go.



Other comments

Results of the compression test will vary engien to engine - but apparently the wanted norm is a MAXIMUM variation of 28 PSI between all 4 cylinders hot or cold .

If there is a substantial change in PSI perhaps a bent valve might be to blame - or worn piston rings or even a bad head gasket.
IF in doubt , take it to a professinal to get a leak-down test + more to find the source of crappy boost :D


http://www.ozhonda.com/gallery/water...=2/79Ywood.jpg

Thats it. Go honda :)

Very good write up. :D . Do you know what the pressure should be for a B16a? like, what is good and what is bad.

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Originally Posted by revNhevN

Very good write up. :D . Do you know what the pressure should be for a B16a? like, what is good and what is bad.

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i have no idea - my totally stock d16a8 - pulled 220 psi ( quite high) - while HOT ( that is , with the car warmed up properly). So , im sure your car could pull a similar number.
As long as each readout is within the 28 PSI range there shouldnt be a problem.

cool write up ben, i should do this :thumbsup:

ur the diy king y0! ;)

yeah, just on this, ideally, the cyllinder pressures should not vary by greater than 5%.

Excellent writeup

cool write up man!! i might give it a go when i have time

Quote:

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Originally Posted by bennjamin

http://www.ozhonda.com/gallery/water...2/7931-med.jpg

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LOL @ step 3

always lookin to make revenue huh bren ;)
nice write up mate

how much 12.5:1 if it were to convert to Psi?

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Originally Posted by pgclee

how much 12.5:1 if it were to convert to Psi?

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thats the compression ratio of an engine. This test is to judge the maximum compression in psi , to test for internal leaks etc.

few queries

1. "turn engine over six times"... i wanan know what this means? as in rev it 6 times?

2. also another thing...where and how much does it costs to get a compression testing tool?

3. does low compression indicate a dying headgasket

Quote:

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Originally Posted by **Ghost**

1. "turn engine over six times"... i wanan know what this means? as in rev it 6 times?

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I think he means to try to start the engine 6 times per cylinder.

Quote:

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Originally Posted by **Ghost**

few queries

1. "turn engine over six times"... i wanan know what this means? as in rev it 6 times?

2. also another thing...where and how much does it costs to get a compression testing tool?

3. does low compression indicate a dying headgasket

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1. "6 times" means , you will hear the engine "crank" 6 times. Its an obvious noise/situation. This is to judge the maximum compression of each cylinder.

2.The tool is about $40-60. You will hardly use it so i suggest to borrow a mechanics ( like i did) or get them to do it for you. Cost = $20 or $30 i guess . It takes only 15 minutes or so.

3.Low compression could indicate a dying headgasket , or bent valves , or worn / leaking piston rings amoungst other things. The most important thing as said before - is that the compression between cylinders does not vary more than +/- 5%.

thanks for that but how do i "crank" it? kinda noob with this stuff.... do i turn the car ON? or something else? completely lost here

Quote:

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Originally Posted by **Ghost**

thanks for that but how do i "crank" it? kinda noob with this stuff.... do i turn the car ON? or something else? completely lost here

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arrgghh dont worry. Just turn it "over" - liek you would to start the car normally. The engine will make a " dun dunnnnn" noise and kep the key in the same position until it does it 5 or 6 times.

nice write up ben! top job

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Originally Posted by bennjamin

arrgghh dont worry. Just turn it "over" - liek you would to start the car normally. The engine will make a " dun dunnnnn" noise and kep the key in the same position until it does it 5 or 6 times.

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hahhahahahha rolf... thanks ben i'll do that!! : ) see u shoulda been more simple in the first place :p

when my car was warm/cold(i left it for about 20 mins) i got 135 165 135 180. but when i redid the test after starting the car and made the engine hot it got pretty much 180 psi across all pistons.

so does the warm/cold reading mean anything??

where do u get said item in step 3? :p
i mite just get one lol

nice write-up. really appreciate it :-) especially the explanations given to ghost.

kristin

Nice write up Benj... get some pants! :p

i plan to do the test on a ZC tomorrow, is it hard to get the spark plugs out?

Ie. is the spark plug remover necessary to get them out?

this test work on carby engines?

tried it and the compression tester keeps sitting on zero for some reason...

well the problem was that the compression tester wouldn't screw in properly, still cant get it to

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Originally Posted by michael_antoi

well the problem was that the compression tester wouldn't screw in properly, still cant get it to

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Which part wont screw in ? The actual head which goes into the engine/spark hole ? Or the top which connects to the gauge ? Try running alittle fresh oil around the head to "seat" it in - and make sure all the gauge lines and screws are tight. Good luck !

not sure what u mean about gauge lines

but the end of the compression tester wont screw in where the spark plugs usually go...

will the temp of the engine vary the read outs?
better to be done when its COLD or WARM

Quote:

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Originally Posted by SKREMN

will the temp of the engine vary the read outs?
better to be done when its COLD or WARM

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yes - at COLD the engine will sometimes give varying compression results ( carbon and very slight dimension differences etc ) But once the engine is at operating tempreture - compression should not vary with +/- 5% of each cylinder. That is , best result = at warm :)

Errmm......

What is the situation with injectors and fuel in this procedure ? ;)

Quote:

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Originally Posted by ProECU

Errmm......

What is the situation with injectors and fuel in this procedure ? ;)

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a big 0 since its all disconnected lol :confused:

Yeah True

I should learn to read gooder...

with my build up-b18c block-ctr pistons and b16a head- i broke in my engine where at 1000km's i tested it...
i read something like 240-225 psi... would you guys think that the compression is too variable?? if i remember how to do my maths right the +/- is variable is about 6.5% differance!

would this efect the tuning and timing or perhaps cause one cylinder to have pre dettanation while the others didnt??

lol i dont want to reseat the rings....mabey i should just close my eyes to it and keep driving coz it runs sweet! just pretend i didnt do the test in the fiorst place;)

I think you should re-try the compression test.

I would be concerned with those numbers you posted...

It might be a case of still requiring to run th emotor in further.

I'd keep an eye on it, and recheck the compression later down the track.

will do :)

I will have to do a leak down test to get a propper diagnostics i think

whys all the pictures the same, a civic

considering u bumped a thread thats almost 5 years old

im thinking the images arent on the server anymore

yea obv lol. just pointing out it should be changed :P

maybe pm bennjamin and ask him nicely to re-upload the photos?

Bump for an old dog.

Does anyone know how to perform a compression test for a motor thats our of a car?

apply power to the starter motor?

awesome write up.
great tip for someone buying an second hand car :)