How to check Compression? - Toyota Nation Forum : Toyota Car and Truck Forums

asm · 07-18-2005, 01:39 PM

I have read up everything I can think of about checking compression. But, I am still confused....

Exactly how long am I suppose to crank the engine?? I notice the first crank bring it up about 120psi and second crank goes about 150psi, then 160psi. All 4 cylinders behavior exactly the same way. So it appears the compression result could be influence by numbers of crank!!!

Since I don't know the proper number of crank needed to reach a correct compression reading, I have decided to crank about 20 times per cylinder... that got me about 170 psi for all cylinders... Any way, the problem is the Gen4 Camry spec says 178psi or more is normal. I suppose I could keep cranking to reach 178psi.

Was my compression check done incorrectly??

ASM

anarkia1ces · 07-18-2005, 02:03 PM

20 times per cylinder? What is wrong with you man?

I would suggest no more than 3 times per cylinder with about 3-4 seconds of crank at a time. Just get the highest reading for each cylinder and compare. There is nothing to it. If the PSI is lower than "normal" (Don't know the specific range for your car), your head gasket/compression rings may be damaged. Squirt a little motor oil in the cylinder with the lowest reading (Or if the reading is below normal on all, do this for all cylinders as well) and retest. If the oil raised the PSI, it's your piston rings gone bad, if the readings are still the same or lower, its your headgasket.

Lord_Anarchy · 07-18-2005, 02:41 PM

Yup, that's all to it.. Cranking 20 times

.. Anyways, good luck and I hope you get the proper numbers

asm · 07-18-2005, 07:12 PM

Well, if I only let it crank over 3 times, I will only get about +160psi. That is waaay below the suggest 178psi. Perhap the harbor fright gauge is wrong?!?!

any one has any experience with the harbor fright gauge?

On the side note, at least I know all my compression are even across all cylinder

ASM

anarkia1ces · 07-18-2005, 08:07 PM

Get a Craftsman compression test kit. Cheap, but efective.

Luckynumber5 · 07-18-2005, 10:18 PM

its fine as long as the #s arent extremely low and all the cylinders are close together

chronoti · 07-18-2005, 10:18 PM

craftsman is not cheap but it is effective

i have the harbor fright gauge in my garage too

bought it thinking my sister might of blew out a pistion in her car but it turned out to be a bad wire

i never got around to using it. let me know if it's just the gauge or something wrong with your car. but a little low like that might just mean a little sluge in your engine something that seafoam wount help out with.

jackfrost1031 · 07-19-2005, 04:39 AM

did you have the throttle wedged open while you cranked? You should.