Compression test?

jason herdahl

jason herdahl

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Jan 5, 2010
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Ok this might be a dumb question but how do u do a compression test and what psi should each cylinder be around and what is the max and min between each cylinder?
 
500psi and you need an adapter that goes in the injector hole. Pull all the injectors out and crank the engine over until the gauge stops going up. Then you've got your reading.
 
Where would I go about finding an adapter for the injector hole? and the cross-over tubes... I guess you screw them back in?
 
4x4 Cody said:
Where would I go about finding an adapter for the injector hole? and the cross-over tubes... I guess you screw them back in?
Click to expand...

no you don't put the cross overs back in! its basically a dumming injector that would be drilled and tapped. Whats the issue??
 
Drilled and tapped where, the injectors aren't threaded. or if you had an old injector and drilled a hole straight through it, how would you keep it from jumping out? drill a hole in the top plate too? or a dummy top plate... I got up to 180psi tops. too many leaks in my tester if the numbers are supposed to be around 500 per cylinder. I just cant see a small leak somewhere losing over 300psi.
 
Not getting the answer I'm looking for fellas.

What kind of tool/? fits in where my injector came out?
lol and where do you find a gauge that goes from x to 500psi? East Austin Tx does not have one above 400 psi.
 
I did a compession test on my truck a while back. Had to get the adapter and gauge from Snap-On but cant remember the cost. The test is simple, its like changing an injector besides you leave the crossover tube out and bolt the dumby in place. I was told to crank an even number of times on all cylinder (ex. 5 revolutions per cylinder). I was able to come up with about 325 psi on #1 and #5, 275 psi on #2, and 300 psi on the remaining. A friend of mine says on all of the trucks he has done they have all been different.

Also the compression tester comes with an injector hold down that has a hole in the middle so the fitting on the adapter can go through there and hook the gauge to it.
 
Last edited:
amikesell said:
I did a compession test on my truck a while back. Had to get the adapter and gauge from Snap-On but cant remember the cost. The test is simple, its like changing an injector besides you leave the crossover tube out and bolt the dumby in place. I was told to crank an even number of times on all cylinder (ex. 5 revolutions per cylinder). I was able to come up with about 325 psi on #1 and #5, 275 psi on #2, and 300 psi on the remaining. A friend of mine says on all of the trucks he has done they have all been different.

Also the compression tester comes with an injector hold down that has a hole in the middle so the fitting on the adapter can go through there and hook the gauge to it.
Click to expand...

does that explain it a little more clear?
 
I can't honestly remember what I did with the crossover tube holes but I know I didn't put them back in for the test. And my truck was hitting 500psi across the board on my truck.
 
If u had the dummy injector/adaptor or whatever it probly won't have the hole for the cross over tube cuz u don't need it right?
 
Compression test on my '96 12v came up with 500-525psi on each hole after 5 compression strokes. Had 355,000 miles on it at the time. I heard a more reliable way to determine cylinder condition is to do a bleeddown test.
 
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