Im out taking compression tests on all my cylinders. What im doing is cranking it, and once it starts shutting it down. Im getting around 150ish PSI in #5 #6. If I let the truck run and release the pressure while running, then let it rebuild in those it only gets up to about 70 PSI. On #7 and #8 when I crank it up it gets to about 120 PSI, but when I release and let it rebuild they too get to around 70 PSI. What should these numbers be at?

-Mike

 

I don't know the right procedure for our engines, but if you disconect the coil pac wires, pull all 8 plugs, and pull the fuel pump fuse it would allow you to crank the engine without it starting.

 

The guy at the dealer tripped the fuel shut off on mine and then cranked it to test. Not sure what is suppose to read though.

Suavy

 

Hmmm... then wouldnt air be sucked strait into the plug holes? Know of any other way to keep it from cranking?

-Mike

 

What Don said, But step on the pedal all the way to get proper readings. In other words WOT

 

I usually just pull the fuel pump fuse. It's right in the box under the hood.

 

Pull out all your coilpacks and plugs, you dont want to fire the motor....put compression tester in one plug hole and turn engine over 5 times (cycle it 5 times) You can count 1 every time starter burps....do the exact same way for all cyclinders....your numbers should be around 150psi for your motor....and the rule of thumb is no variance of more than 15% between cylinders...ex. if your lowest cylinder is 135 psi than your highest cant be more than 155 psi.....if so you got a problem..

 

I dont leave plugs in due to possibility of burning up starter....its a lot of strain and heat on starter with plugs in.....

 

Pull the plugs, disconnect the injectors and test at WOT.

Mark

 

The worse 3 words a L owner can hear

I can pull the Motor of a BB Chevelle
faster than doing our plugs

Good luck Mike, this sucks..........

 

Make sure you cycle motor over the exact same way, 5 times ,for all cylinders while doing compression check.....consistency is important....

 

At WOT? Is this true? Why?

 

will the cheapy testers at pep boys work? i have one, but i am scared to use it due to the number of threads it has. i am afraid it will hit a piston screwed all the way in...

 

It lets the maximum amount of air past the throttle plate.

 

Don't you also want the engine at operating temp? thats the fun part!