i did a compression test today
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i did a compression test today
today myself and a friend checked my compression the way i was told by him.that way was with the engine cold, not warmed up.what we did was just took the plug for that cylinder out, place the plug in the dizzy wire and then put the gauge in the cylinder have one person crank over the engine while holding full throttle and let the gauge read 3-4 times. heres what the results were :
cyl. 1 170
cyl. 2 150
cyl. 3 170
cyl. 4 170
cyl. 5 160
cyl. 6 160
cyl. 7 160
cyl. 8 150
now i know the above procedure is different from the haynes one but i never had done this before and my buddy went to college for this stuff so i followed his advice...
anyway haynes said that as long as the lowest number was within 75% of the highest number the compression is good.only thing i don't know is if by doing the above test procedure compared to the haynes procedure if you can go by the 75% margin.
now i know that this isn't a test to check if your engine is bad but just part of that overall testing . i was just checking for the compression.
if anyone has some thoughts they feel i should know please post. thank you.
cyl. 1 170
cyl. 2 150
cyl. 3 170
cyl. 4 170
cyl. 5 160
cyl. 6 160
cyl. 7 160
cyl. 8 150
now i know the above procedure is different from the haynes one but i never had done this before and my buddy went to college for this stuff so i followed his advice...
anyway haynes said that as long as the lowest number was within 75% of the highest number the compression is good.only thing i don't know is if by doing the above test procedure compared to the haynes procedure if you can go by the 75% margin.
now i know that this isn't a test to check if your engine is bad but just part of that overall testing . i was just checking for the compression.
if anyone has some thoughts they feel i should know please post. thank you.
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From: northeast, KY
I don't know about the haynes manual (don't have one...) but I always pull all the spark plugs to do the test. This will let the motor turn over alot easier and your start will be turning the motor over alot quicker, and give you a more accurate (real life, I guess) reading.
That's pretty good compression, in my opinion. The last time I did mine the top # was 120 and the bottom was 45... needless to say it was pretty well shot...
Matt
That's pretty good compression, in my opinion. The last time I did mine the top # was 120 and the bottom was 45... needless to say it was pretty well shot...
Matt
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From: Island Southeast Alaska
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will do.i found a couple of things that may be a problem. cylinder #4's plug boot was melted and the metal was showing,this could be the culprit in my misfire problem ?? they were motor craft wires and under a life time warrenty so i got another set for free. that was cool.
i have an emmision tube/hose that is dry rotted and has a hole in it. im sure this could be causing problesm as well.what im not sure, lol
i have an emmision tube/hose that is dry rotted and has a hole in it. im sure this could be causing problesm as well.what im not sure, lol
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Originally Posted by fishin machine
Yeah that melted boot is probably the misfire issue. Which emmisions hose is it?
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From: western montana
MTTHWVN73:..........
edited as i know twisted's test didn't use oil.....
you don't squirt oil into the cylinder when checking compression unless your diagnosing a problem cylinder.
You remove the plugs on a cold engine...no sense burning yourself...and test each cylinder...keep an eye on how fast the pressure bumps up...they should jump up to pressure fairly consistently and within a couple turns...typically 3 at most.
If you have a cylinder that shows low pressure you can squirt some oil into it to see if it's likely to be rings or valve. The oil will help seal worn rings so if you test with oil and get improved pressure it's likely worn rings/cylinder...if the pressure still sucks badly ie doesn't change much from original test it's more likely to be a bad valve which is better news than the rings.
If you use oil from the start you remove the possibilty of worn rings and your really only testing the valves...if that makes sense.
I hope that helps a bit.
edited as i know twisted's test didn't use oil.....
you don't squirt oil into the cylinder when checking compression unless your diagnosing a problem cylinder.
You remove the plugs on a cold engine...no sense burning yourself...and test each cylinder...keep an eye on how fast the pressure bumps up...they should jump up to pressure fairly consistently and within a couple turns...typically 3 at most.
If you have a cylinder that shows low pressure you can squirt some oil into it to see if it's likely to be rings or valve. The oil will help seal worn rings so if you test with oil and get improved pressure it's likely worn rings/cylinder...if the pressure still sucks badly ie doesn't change much from original test it's more likely to be a bad valve which is better news than the rings.
If you use oil from the start you remove the possibilty of worn rings and your really only testing the valves...if that makes sense.
I hope that helps a bit.
Last edited by roger dowty; Jun 2, 2007 at 01:06 AM.
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