compression test

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syty9933

New member
im testing it now and i didnt run it first and i also dont have a battery charger hooked up. On my first cylinder that i think wouldnt be blown out of all of them im only getting 60psi. Does that seem possible if i didnt run it first or if i have bad cranking power?
 
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syty9933

New member
Re: compression test

if i test them all and they are this low but are within eachother, will it tell me that my motor is good, or should i put the plugs in and run it first?
 
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syty9933

New member
Re: compression test

i hadnt started it up for several days before i tested it, so should i warm the truck up first then try it again? and ive never heard a misfire
 
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turboj91

New member
Re: compression test

Warming it up is not going to get you from 60 to 140+. Keep going and watch and listen to your cranking speed. As that other guy stated, if is still cranks the same speed on the last cylinder tested, the battery is not your issue. If you have a digital meter/tach to watch cranking speed, you can trust that more than your ears. 60 is not a good starting point so I would not get your hopes up unless it is for an excuse to do a complete rebuild. Good luck.
 
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syty9933

New member
Re: compression test

Ty0331 said:
It won't help a 60 much. A few days doesn't make any difference. I never warm them up, or even start them. Much easier to work on a cold engine. You're really looking for relative results. Ie, the trend among cyls. Let's suppose they come up 140-135-140-150-145-60. The 150 is a tad high, suspect carbon, or oily-residue build-up. The 60 has a major problem. The others are a bit low from the "expected" value of 145-155, but are pretty much the same. Suspect that it's cranking speed, or cold temperature, something like that. But not a problem.

You're looking for the trend, with the "expected" result to be 145-155.
Click to expand...

so if i tested the others and they came out around 60-70 then its somthing else possibly?
 
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syty9933

New member
Re: compression test

i did #1 and #5 so far and #1 is 60psi and #5 is 140psi, how much motor oil do i put in to see if its a ring or a head?
 
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syty9933

New member
Re: compression test

ive only done 3 cylinders so far , but i tried the oil trick on the one low compressed cylinder and it seemed to stay the same. How much should i expect the pressure to change if i put in oil and it goes up, because of bad rings?
 
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