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06-07-2009
Today I was fiddling around trying to get a reading for compression. This is my first time doing this. I have a very simple needle gauge that connects into the spark plug hole. I was cranking the motor by hand for a while (big pita) and the most the gauge read was below 30psi. I then tried the next cylinder and it did the same thing. Am i not using the gauge correctly? How is this done? Would the reading be off if there isn't a t/b and some vacumme lines are un-done?
06-07-2009
for reference my gauge looks like this
06-07-2009
you dont crank the engine by hand, you unplug the ignition module, cuts spark and fuel and you crank it for about 5 sec. that hose has a schrader valve correct? you will need one so it holds the reading for you
06-07-2009
Yes it does have that schrader vavle. Someone told me to crank it by handOriginally Posted by minichopper6hp
. Ill try cranking it, would it matter if i don't have a throttle body and some vacumme lines are un-done?
06-07-2009
why would you crank it from the inside of the car? that would turn the motor over and you wouldnt get a solid peak reading...
06-07-2009
what?! thats how you do a compression check. it has the schrader valve there to hold the max reading.
whoever told you to crank it by hand is wacked out
06-07-2009
i have DONE it by hand. mine doesnt have a valve on it so i HAVE to do it by hand and hold it at TDC to get the reading.
06-07-2009
i have done it by hand and by the starter and the results where night and day. the readings that i took on the starter where much higher than the ones done by hand. my gauge also does not have a valve on it but the gauge it self saves the highest reading then i need to push a button to release the pressure. One of the times i spun it by hand i was only seeing 30psi and it turned out the timing was off. i had the crank key way at 3oclock and not 2 oclock on the RM timing set
06-07-2009
I was seeing below 30psi and i didn't touch the timing, only thing was i removed the harmonic balancer and it ran fine before i took the motor apart. Did i do the compression check wrong?
06-08-2009
try spinning it with the starter and see what you get for pressure then. now where you getting below 30 on all cylinders or just 1??
06-08-2009
you guys think im dumb but the proper way to do a compression check is with the starter. I dont pay $30k to go to a well known automotive school to get false information
06-08-2009
Im with minichopper6hp
we used a remote starter hook up when we checked compression and let it go for about four to five "puffs" with the ignition disabled And fuel pump relay fuse pulled
We had 3 clesses where comperession tests were taught.
And thats from 3 college instructors with over 80 combined years exp
06-08-2009
like i said. i HAD to do it by hand because of the gauge i was using. no one says you guys were wrong, that is just the only way i knew how to do it.
06-08-2009
You will never get an accurate reading doing a compression check by hand. I have never heard of such a thing.
06-08-2009
I started with the #5 cylinder when it read below 30, then i moved to the #3 cylinder and got basically the same thing, then i stopped because i figured i wasn't getting anywhere, I didn't crank as many times on #3 because I thought i was doing it wrong.
06-08-2009
I did... its called WyoTech.
Though it can be done both ways. Though usually not by hand.
06-08-2009
that sucks, i go to UTI
06-08-2009
Im going there tomorrow to possibly sign up
06-08-2009
which one you going to go to?
06-09-2009
The one in PA. Which one do you go to?
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