How long to crank when doing compression test?

[LAC_STS]

I looked around the net and there are a bunch of different answers. Figured I would ask you guys.

When doing a compression test how long do you crank the engine for? Do you do it until the gauge doesnt increase anymore or a certain amount of "puffs", or certain amount of seconds?


Much thanks

 

[tazrig]

Re: How long to crank when doing compression test?

3 or 4 cycles or puffs as you call it should give you a good reading.

 

[Bondo]

Re: How long to crank when doing compression test?

Ayuh,.... It really don't matter,...

The gauge will move Up, til it don't, no matter how long ya crank it over,...

 

[lynnboy021]

Re: How long to crank when doing compression test?

make sure you are at WOT,. have a full charged battery, and disable the fuel cuz if fuel goes inside the motor you will have a false reading... also if you have lets say 110 psi and one at 130 put a spoon of oil in the 110 psi and recheck, if psi goes up then your rings are gone..... just some tips for ya

 

[LAC_STS]

Re: How long to crank when doing compression test?

Ayuh,.... It really don't matter,...

The gauge will move Up, til it don't, no matter how long ya crank it over,...

I wasnt sure if you were supposed to crank it where it only compresses that cyl one time or until the gauge doesnt go up anymore. The first compression reads about 100 but after a couple it will read about 160 170 PSI on all cyls.

 

[jerryjerry05]

Re: How long to crank when doing compression test?

Stop when it stops going up.
Remove all the plugs then do the test.

 

[Scott Danforth]

Re: How long to crank when doing compression test?

many years ago, my crusty ASE certified shop teacher informed us, 5 "puffs" for each cylinder. If you do not build pressure after 5 revolutions, your wasting your time

you want to watch the gauge as your doing this. a large bump on first revolution followed by slightly increasing pressure with each revolution is a healthy engine. a low pressure with slow increase between each revolution - add oil to the cylinder and retest. usually a sign of worn rings.

 

[LAC_STS]

Re: How long to crank when doing compression test?

many years ago, my crusty ASE certified shop teacher informed us, 5 "puffs" for each cylinder. If you do not build pressure after 5 revolutions, your wasting your time

you want to watch the gauge as your doing this. a large bump on first revolution followed by slightly increasing pressure with each revolution is a healthy engine. a low pressure with slow increase between each revolution - add oil to the cylinder and retest. usually a sign of worn rings.

Yea that's what mine does. Was wondering if that was normal. First puff goes up to 100 or so then each puff gives it a little more until after 4 or so it's at 160 - 170. That's was my point in starting this thread was to see if the first puff (100) or the 160 - 170 was the correct result.

 

[Bondo]

Re: How long to crank when doing compression test?

Yea that's what mine does. Was wondering if that was normal. First puff goes up to 100 or so then each puff gives it a little more until after 4 or so it's at 160 - 170. That's was my point in starting this thread was to see if the first puff (100) or the 160 - 170 was the correct result.

Ayuh,... Sounds like a healthy motor,...