I want to do a compression test on a used motor I just dropped in my car !!! It supposidly has 65000 on it and has the ATF put in it and turned over by hand since the guy puled it from his car. I tried to start it today but all it did was spin over very fast and flood !!! It did smoke out the pipes like it was tryin to start but never did and it got to dark on me to keep tryin.
So back to the test doe sit have to be warm to get a good reading or will it give me something at least to know if it is a good motor?

 

you can do the chug test on it if you can't start it...turn the eccentric shaft pulley, you should here a port open (the swoosh or sound) every 1/2 turn of the shaft. You can also remove a plug on each rotor and put your thumb over it and turn the ecc. shaft, if it has good comp. it will give your thumb a good push. These arent completely accurate though, a compression test is way more accurate. As for your ? about the engine needing to be at OT for a compression test, i believe so.

 

It will give you a reading cold, but all vehicle manuals and any sort of shop tech data will recommend it be done at operation temp. What he is saying about putting your thumb over the hole, if the compression is good, it will push air out the spark plug hole and try to push your thumb away. 3 apex seals means you have to get 3 good pushes on each rotor. If you crank the starter and listen to it, you should here 3 "swoosh" sounds that sound the same. If you hear "swoosh, swoosh, pssss" that is bad. Thats the best way to describe the sound. If you have a gauge, you can use it instead. I'm assuming you know how so I will end the thread here. Feel free to PM me if you have more questions.

 

thanks for the info !!! Another question for you to get this thing started should I use ATF in it or oil I hear paople say either one if you got starting problems ? If so how much of either do I put in the rotor ? Thanks

 

check out rxlexi post. Thay just sad evreything u need to know.