Compression testing?

[MelScrilla]

How do i do it, i got one of the thingys but i don't know how to use it?
BTW im new where is the new member forum??

[wed3k]

1. remove spark plugs
2. hold throttle body to wide open
3. screw in guage to first cylinder
4. turn the key in ignition so the motor cranks 6 times.
5. record reading.

it shouldnt be more than 175. if you have a low cylinder, squirt a tiny bit of oil and see if the compression changes. if it does, it usually means the piston rings are toast.

[MelScrilla]

Ok i understand everything else but why do i have to hold the throttle open??And do i remove all the plugs when i crank it won't that squirt oil out??

[wed3k]

Ok i understand everything else but why do i have to hold the throttle open??And do i remove all the plugs when i crank it won't that squirt oil out??

it wont squirt oil out because oil is splashed onto the walls of the cylinder under the piston. the other holes are being vented to the atmosphere, so there are no pressures being created which means no oil flinging.

in theory, a closed throttle body will restrict the piston from making peak compression but i have not seen a difference. it was just how i was taught and did the procedure.

[EXR-ALB]

Won't squirt oil but be sure to remove fuel pump relay or fuse as to stop the injectors from loading the cylinders. I know my testors don't like to be filled with fuel. A little is ok but not a lot. Also holding the throttle open or closed, Iv'e done a billion compression tests and never had a difference weather it was closed or open, but everyone has their way.

[Smoken_ducky7]

Won't squirt oil but be sure to remove fuel pump relay or fuse as to stop the injectors from loading the cylinders. I know my testors don't like to be filled with fuel. A little is ok but not a lot. Also holding the throttle open or closed, Iv'e done a billion compression tests and never had a difference weather it was closed or open, but everyone has their way.

The way i did it was i unpluged the distributer and pluged in the compresion tester and just turned the key it will read that way i didnt hold the th bod open sounds no good

[f22Trini]

So a minimum reading of 175 is good? what about maximum?

[wed3k]

So a minimum reading of 175 is good? what about maximum?

max is 175.

[Night Wolf]

1. remove spark plugs
2. hold throttle body to wide open
3. screw in guage to first cylinder
4. turn the key in ignition so the motor cranks 6 times.
5. record reading.

it shouldnt be more than 175. if you have a low cylinder, squirt a tiny bit of oil and see if the compression changes. if it does, it usually means the piston rings are toast.

dont forget to first disconnect the other sparkplugs too. also do it in order of compression.
cyl #4(4th)
cyl #3(2nd)
cyl #2(3rd)
cyl #1(1st)

btw... chances are your not gunna get prefect numbers. but they should all be with in a 15 PSI range of each other. if one is 90 & the others are 140-150 than that one 90 PSI has got a leak some where.


after you do the test, you can proceed to a leak down test. if somethings wrong

[cloudasc]

If max is 175, then what does it mean that I got 185, 180, 185, 185 for my compression results on my stock a1? 176k on the motor, and still pulling hard! I am about due for a timing belt job, could this affect my results?

[d112crzy]

Most f22's I've compression tested have all been above 175psi. Probably due to all the build up on the pistons.

[ibr_adam09]

3 1/2 month old thread ...

[scudweiser]

YOU'RE a 3 1/2 month old thread...



theres a DIY now for this...

[ibr_adam09]

^^^ that doesn't even make sense >_>