compression testing q's

[phrozen]

Sorry for this post and not searching but i have to go compression test a motor today and im wondering how id go about doing it. The thing is the harness is not hooked up to the car and there is no intake and exhaust piping but the manifolds are there. The motor has 75k on it i just want to make sure theres nothing wrong. Could someone explain to me how i would go about jumping the starter and if it would work without the harness or antyhing hooked up

[DuffMan]

The starter is controlled by the lower harness, not the main engine harness, so if you have the lower harness you should be good.

Otherwise you need to jump it by sending +12v to the little terminal that the plug plugs onto.

[phrozen]

so all i have to do is hook up the lower harness and i should be good? what about the injectors? im trying to run the motor till it gets hot so i can get an accurate reading.

[kandyflip445]

I don't know if you can do that then if the ECU is unplugged.

[TheTicTac]

Like Duffman pointed out all you have to do it get the starter to work. You are just testing if the piston and it's rings can compress air in it's cylinder. If the numbers come out good then there is a high percentage that the motor is acceptable.

[kandyflip445]

But with the engine cold the numbers may come out lower than normal. I don't see him getting it to run without it hooked to the ECU. But, yes you can get the test done without it.

[fliprayzin240sx]

Well cold will get you a general idea. May not be 100% accurate but its something. you doing a comp check on ur KA jason? Like everybodys saying, all you need is for the starter to kick off. Listen to the engine and let it spin 5 times and thats should give you some number. I cant remember whats the minimum you should be getting for the KA but if its your KA...itll probably be lower than its supposed to be *170 ish i think maybe higher* but if you get something lower and they are all within roughly 15psi of each other thats aites for now.

[BlackS14]

I don't think the numbers will vary much when concerning whether it's hot or cold......doing it cold will give you a really good idea on what the number would be when hot...I did a compression test on my Ka (with a brand new tester mind you) recently (has 120,000+ miles) and got 180 across the board......those numbers work for me....haha

-Bill