Compression test help please..

[davidjepson]

I want to do a compression test on my car to see if the engine is ok. when do you do the test? I have the guage. Does the engine need to be at running temperature and do you test the car at idle or do you rev the engine up a bit? DJ

 

[jjs]

i would do it when the engine is cold, remove all the plugs, then connect the gauge, crank the engine over for a few seconds then check reading, then move onto next cylinder, if any readings are low, you can ad a teaspoon of oil to the cylinder through the plug hole, then recheck if reading is higher there is a good chance it is a problem with rings or pistons, if no change could be valves or head, then you would be looking at doing a leak down check,

 

[davidjepson]

ok thanks. Why do you need to remove all the plugs can it be done one by one? DJ

 

[PobodY]

Remove the plugs so that it doesn't fire!?

 

[jjs]

also if there was a leak from the head gaskek etc, if you left the plugs in you may get a false reading as you could get pressure leaking from the cylinder next to the one you are testing leaking into the one you are testing . jim

 

[davidjepson]

What PSi/Bar should a standard engine be and what would a rebuilt engine with low comp pistions be? DJ

 

[P11SR20DET]

What PSi/Bar should a standard engine be and what would a rebuilt engine with low comp pistions be? DJ

^^^Ditto...:roll::roll:

 

[jjs]

hi standard is 11.5 bar or 164 psi, minimum 9.5 bar or 135 psi, @ 300 rpm,not sure what engine cranking speed is, max difference between cylinders is 1.0 bar or 14.0 psi, for standard engine , taken from nissan service manual, hope this helps, im sure the last check i did on an engine was 10.0 bar, and engine was running fine , that was checked at engine cranking speed,all plugs removed