how many cranks do u guys usually do ???
thanks

 

I do about 4-6..

Adi

 

errr do u just wait until the niddle stop moving or do have to keep it constant , ( says like 6 cranks for all 4 )

 

thanks


[Modified by VTEC_SiR, 8:08 AM 2/12/2002]

 

crank the engine over 4-6 times check the gauge and do that for all of your cylinders.....

Adi

 

Yeah i usually just crank it over about 5-6 times, by that time the needle is probably as high as its going to get. So if your doing that, your most likeky getting a good reading. HTH

 

What happens when it pops? Is that normal? I remember doing a compression test a while back on my car and just about every cylinder popped. at about (120-150 psi) needle didn't stop moving til about 200 psi. Didn't seem to mess anything up because the car ran fine. Have done compression test on my friends cars as well and they pop too(sometimes). What is causing that?

 

You really shouldn't let it crank more than 5 times at most. Simply letting it crank till it reaches compression doesn't tell you much. The engine *should* reach 85% compression by the 2nd full stroke per cylinder, and *should* be at 100% compression by the 4th stroke. Now obviously this is a motor operating at 110% new conditon, so a motor with decent mileage will take a bit longer, but by the 5th crank you should know what the condition of the compression per cyliner is. And don't forget to do this with a warm engine and with the throttle open.

 

Hmm so if i'm cranking them all until the needle stops, and they all stay 200, but it took 7 or 8 cranks, is it still possible that some of the cylinders are bad and I should retest with a set # of cranks?

-Xerxes

 

The longer it takes to compress all the way, the weaker the rings are (or something like that, my tech buddy explained to me a while back heh). This is why you use a set amount or 4-5 cranks max. and see where you are with compression. BTW it's awfully strange for your piston to have to compress 7 times to reach full compression. Are you sure the engine was warmed up?

 

Well actually last time i did compression tests i just cranked until the needle stopped moving. I never even counted the number of cranks but i know that sometimes we let it go for a while just to get that extra 5-10 psi on the gauge hehe

 

ok so its that mean if my rings are bad the #'s will be low ???

 

Well if the #'s are low, it's usually bad rings

 

What all goes along with doing a compression test? Is this right?

1. Take fuel pump fuse out
2. Take spark plugs out
3. Screw in compression gauge
4. Floor gas pedal
5. Crank it 6 times

Is this correct? Also, does it matter what brand gauge you have? Like if it is a $35 one from a auto store? Thanks