I just bought a Mitsubishi U42T with a 3G83 engine in it. Looks like it spent most of it's life in storage. Found #3 exhaust valve stuck and rocker arm broken. After replacing parts and sending cylinder head out for repairs, I am putting it all back together. Now I am getting only 10-30lbs of compression in my cylinders. Bad Rings? In correct timing? Not sure whats going on. Seems if the rings were bad I would still be getting a higher reading. Any help is greatly appreciated.
sounds more like WAY wrong valve timing to me, bad rings should still get you close to 100. I expect a wet test would not improve those numbers. Either the valves aren't sealing or it's timed wrong.
My mits is the same way but on #1, smokes like a train, #1 only has 80ish psi. When I put it at TDC and put air in the spark plug hole I hear and feel air rushing out the exhaust pipe so I've either got a burnt valve, bad seat, or something with the valve train. putting a little oil in the cylinder did not help the compression on mine. I guess I'll pull the engine this winter.
