So what would the correct psi...

[xj_dummy]

On a compression test for a 1990 with a 4.0 with 150,000 miles?

[Geonovast]

Good compression is 120-150 in each cylinder with an average of around 130.

[jtdesigns]

Good compression is 120-150 in each cylinder with an average of around 130.

or 10% difference between all the cylinders.

[JeepcoMJ]

yea.

 

FYI to the original poster.

 

mileage has NOTHING to do with compression. only the engine's maintenance history has anything to do with it.

[xj_dummy]

I'm mainly concern that I might have a blown head gasket.

The truck has been sitting for a while now and i would like, OOPs, MY WIFE wants it running soon so she can drive it.

So if I get good compression on it, next is an open radiator system. Please hold your tounge. I have heard the good the bad and the ugly on open and closed systems. And also I'm going to change out the ABS :ack: system on it to a non ABS :ack: system.