Compression. WTF
05-05-2009, 07:36 PM
#1
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Compression. WTF
Bought car with 0 compression in any cylinder.
Opened up, timing belt on cams was dead on, crank sprocket was off by about 30 degrees.
Replaced timing belt. Did compression test with cheap harbor freight tester and weak battery (hooked up to charger on 10 amp setting):
Cyl - PSI
1 - 150
2 - 120
3 - 120
4 - 120
Compression! I've got it! But, why so uneven? Check Cyl 1 again... 150, wasn't a mistake.
Hmm... Two tablespoons of oil down Syl 1, check again. Holds 0 psi! Wtf? Test other cyls... 0 psi all down the line.
Timing belt is still set correctly.
Ideas?
Opened up, timing belt on cams was dead on, crank sprocket was off by about 30 degrees.
Replaced timing belt. Did compression test with cheap harbor freight tester and weak battery (hooked up to charger on 10 amp setting):
Cyl - PSI
1 - 150
2 - 120
3 - 120
4 - 120
Compression! I've got it! But, why so uneven? Check Cyl 1 again... 150, wasn't a mistake.
Hmm... Two tablespoons of oil down Syl 1, check again. Holds 0 psi! Wtf? Test other cyls... 0 psi all down the line.
Timing belt is still set correctly.
Ideas?
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05-05-2009, 08:11 PM
#2
No seriously, I'm not sure exactly what could be going on, but compression shouldn't go from decent values(despite being uneven) to non existent.
The only thing I can think is that valves are somehow staying open. That is the only variable that could change between runs since even bad rings wouldn't change like that.
EDIT: Sorry I'm not more helpful.
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05-05-2009, 08:16 PM
#3
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So I said "**** it", threw new plugs in, the coil pack, plug wires, and the airbox. Popped the fuel relay back in.
******* car started right up the first time I twisted the key.
Didn't stay running long, but then again I didn't want it to.
Good enough for me. Going to pull the engine and do the manual tranny swap.
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05-05-2009, 10:12 PM
#6
YOU COULD HAVE DONE IT WRONG.
No, seriously.
If you put oil into the cylinder and then cranked it w/ your tester in the cylinder you could've gotten oil up into your gauge/hose assembly on your tool and it could now be FUBAR. But, it's Harbor Freight, and that happens... good thing they're only $6.
I did that when checking my Saturn anyway.
What I was advised to do was:
check compression on warm engine the regular way WITH A NEW GAUGE.
If doing a wet test, add oil the cylinder, put a rag over the valve cover and crank the engine 3 seconds. NOW do your wet test on that cylinder. Repeat for other cylinders.
Now... if you did your test like that, I've just wasted my time and when you pull your engine you should stuff your ***** in a freeze plug to show it YOUR THE BOSS.
No, seriously.
If you put oil into the cylinder and then cranked it w/ your tester in the cylinder you could've gotten oil up into your gauge/hose assembly on your tool and it could now be FUBAR. But, it's Harbor Freight, and that happens... good thing they're only $6.
I did that when checking my Saturn anyway.
What I was advised to do was:
check compression on warm engine the regular way WITH A NEW GAUGE.
If doing a wet test, add oil the cylinder, put a rag over the valve cover and crank the engine 3 seconds. NOW do your wet test on that cylinder. Repeat for other cylinders.
Now... if you did your test like that, I've just wasted my time and when you pull your engine you should stuff your ***** in a freeze plug to show it YOUR THE BOSS.
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