from a 93 factory shop manual, should cover a few years. hope its usefull for someone

http://shbox.com/1/4th_gen_tech2.html#opti_test

 

New sticky. Thanks craby.

 

Letting the oil set in the cylinders isn't going to do any good for the compression test now. I don't know how you're performing your test, but the fact you got a backfire tells me you're not doing all of it quite right. You want to first check the compression dry on a warm engine, with all the spark plugs out. Removing all the plugs helps you to get the engine zinging over good and fast. When checking each cylinder, give the engine a good 6-8 rotations. Then for the wet test, squirt some oil (about a teaspoon), aiming high in one cylinder only. Turn the engine over a couple times to let the oil work in, then reinstall the gauge and take another reading the same way you did the dry test. If the reading jumps, your rings are worn, but a little bit is to be expected. But, if the numbers jump a lot, your rings are worn a lot.

 

Just to add to the above, you need to be 100% sure you disabled your ignition and fuel systems during the compression test. Not being able to fire a charged coil is really bad for the coil but worse is 8 cylinder shooting out gas and live wires trying to firing spark in your engine compartment. I have seen more then one car set on fire during compression tests.

There is a leak down test you can do to check where the compression is being lost. (search leak down test on You tube). You can also buy a cheap plug adapter and pump compressed air into the cylinder and try to hear where the major leak is.

After reading the whole thread I am getting the feeling you have a another issue and you did the compression test wrong. They tell us in school you need 100 PSI of compression for the fuel to atomize and to get a motor to run but you should be back firing like crazy if low compression is the issue. Another possible issue is exhaust back pressure (plugged cat)

Here is my normal "what to do with a no start"

1.)Crank car does it sould like it has compression?
2.)Check for spark, is it hot enought? (spark tester)
3.)Check for fuel pressure. (fuel pressure gage)
4.)Check for signal to injector (Use noid light)
5.)Check exhaust back pressure. (Pressure gage, Some vacuum gages have pressure sides)
6.)Pull plug and make sure they are not flooded our. (a wet plug with not fire )

I can not remember ever having a car that had all the above ok and did not atleast backfire or spudder and I have fixed a lot of no start cars

 

chart c4

 

 

Thank you very much