for an older (92) 5.9 non turbo;

this is my first time checking compression on a diesel,

I borrowed a diesel compression tester,

pulled an injector, and screwed in the correct adaptor, (I only have the adaptor for the injectors, not one for the glow plugs)

snapped on the air hose/ guage, and had someone crank the engine over for ~15 seconds....

the needle kind of bounces, (between about 75-200psi) but never really gets above ~200 psi... It quickly (~1 sec?) drops back down to 0 after we stop cranking...

I was told that it should be upwards of 400, but couldn't find anything about this in the book that I have...

I thought that I might have an air leak, and tried tightening down all of the connections, and feeling for air escaping, but no obvious leaks...


shouldn't the guage hold the pressure for a little while? do I have an air leak or a bad tester? The truck was running and starting fine, I just wanted to check things out...

Any help with the issues described above, or in describing the process would be very greatly appreciated.

thank you,
Greg

 

The only tester I've used held pressure until you pushed a shreader valve in.

 

Sounds like the gauge has a problem, most of them have a check valve to hold the reading. As long as you're getting even readings across the cylinders the engine is likely fine.

 

Yes, the gauge should pump up and hold the reading. As long as the motor is running good, and not smoking, and the pressures are even, it should be OK. Also, you don't have glow plugs.