weird Compression Test Results

[EclipseGSX012]

Okay guys/girls

So i try to swap the coilpack out since my old one was coilpack was arching but after me trying to swap out the coilpack the car wont start. Yes i know the firing order 4-1-2-3 which was on correct but for some odd reason car wont start.

Basic car info
6bolt swap w/2g piston on it
the engine it self has between 7000-8000 mile on it.

So 2 of the fellow member from jersey came over to check out what was wrong so they test to see if there is any spark from the wires. After testing for the sparks there was sparks & fuel so next test was compression test about hr 1/2 later. It came out to be 175-75-120-75 [4-3-2-1]. What i was wondering was while checking for the sparks did the cylinder was getting fludded with fuel that cause the compression reading come out bad??

Thank you,
Joe

 

[thornton22050]

in my opinion it shouldnt make a diffrennce plus all of your cylinders would read wrong you have one cylinder that is reading normal while the other 3 are very low

 

[toybreaker]

Yes, the injected fuel can/will cause a reduction in your compression gauge test readings.

It can also result in some other problems, from scuffed bores to ring damage, to diluted engine oil, depending on how much fuel is injected and how much you crank the motor over when it's full of fuel.

It can also result in an engine fire, if you're unlucky enough to light the mix in the cylinders off with a spark from the end of a plug wire. tease: It took my buddy a month or two to get eyebrows back )

I usually just unplug the injector resistor, and that removes power from the injectors.

 

[EclipseGSX012]

Yes, the injected fuel can/will cause a reduction in your compression gauge test readings.

It can also result in some other problems, from scuffed bores to ring damage, to diluted engine oil, depending on how much fuel is injected and how much you crank the motor over when it's full of fuel.

It can also result in an engine fire, if you're unlucky enough to light the mix in the cylinders off with a spark from the end of a plug wire. tease: It took my buddy a month or two to get eyebrows back )

I usually just unplug the injector resistor, and that removes power from the injectors.

Hmm ic thank you for letting me know it will effect the compression test reading but shouldn't it effect all 4 cylinder?

Yeah while they were checkin for spark i did crank it 3-4 time to see if it was getting spark and let the car sit for about 1 1/2 later did the compression test.

Yeah we were lookin for MFI fuse but couldn't find it so we took the harness off from the fuel rail to disconnect the fuel from firing.

So after all those thing one guy did the compression test called the guy who tested sparks and he told him that car does want to start but it doesn't so we can't figure out the problem. So he wanted to see hear it so i plug the wire back on correct order and then try to start the car, it crank and back fired.

What i dont get is that what would be causing the compression low? fuel in the cylinder? bad valve [stuck open]? or blown headgasket? bad ring?

When we check the dipstick oil was fine no coolant mix in the oil. I really need to figure this out so i could get my car running.

Any help will be appreciate.

Thank you in advance,
Joe

 

[bmwisthekey]

Also helps to have the engine warm when doing the compression test but since you cant get it started its kinda hard, as for trying to figure out the culprit in the low readings a leak down test would be very helpful.

 

[toybreaker]

^^^ I agree, a leakdown test would be very helpfull.

It sounds like the tool situation may be limited, however.

Something you can do yourself, (now that it won't start) is to verify the valvetrain timing marks. It's possible it skipped somewhere along the line. Your original compression on #4 sounds like it's all good, but stranger things have happened.

I would also give the entire engine compartment a visual inspection as well. You're looking for unplugged harnesses, and/or undone ducting/intercooler piping, etc.

When you have a lot of cooks in the kitchen, sometimes things can get a little messy.

Is the coilpack you swapped in a known good part? (Does it run in another car?)

Can you log the car? Sometimes, you can catch a bad cas, even though the car won't start. Just crank it over and watch for an rpm signal. Also, check the coolant temp, etc...

Good luck, and keep us posted.

 

[EclipseGSX012]

^^^ I agree, a leakdown test would be very helpfull.

It sounds like the tool situation may be limited, however.

Something you can do yourself, (now that it won't start) is to verify the valvetrain timing marks. It's possible it skipped somewhere along the line. Your original compression on #4 sounds like it's all good, but stranger things have happened.

I would also give the entire engine compartment a visual inspection as well. You're looking for unplugged harnesses, and/or undone ducting/intercooler piping, etc.

When you have a lot of cooks in the kitchen, sometimes things can get a little messy.

Is the coilpack you swapped in a known good part? (Does it run in another car?)

Can you log the car? Sometimes, you can catch a bad cas, even though the car won't start. Just crank it over and watch for an rpm signal. Also, check the coolant temp, etc...

Good luck, and keep us posted.

Yeah i really should have get the leak down test done to figure out what's is causing the low compression on 1&3 and little bit of 2. I'm going to contact the guy did the compression test to see if he could help me out next week to do leak down test.

Also timing was good. I did inspect the entire engine compartment, no unplugged harness or undone intercooler piping. I double check on everything but no loose connection.

I'm not sure i didn't actually try with the 1g coilpack i have but 2g coilpack does get spark but i'm thinking about trying to test it out on the weekend since i need to go to PA for school. So this weeekend coming up try with 1g coilpack 4-1-2-3 and 2-3-1-4 to see if the car would start.

No actually i dont have log for my car. There couple things i could think of that cause the car not to start bad ecu, bad cas and of course maybe the low compression [which everyone is confused since even tho compression is low car should start but run weird]. So hopefully this weekend get the leakdown test to see what is causing the low compression.