How exactly do you do it? I have never done it before, but I bought the tool and tried it today, and when I pressurize the cylinder the engine just spins backwards until one of the valves opens, so it doesn't tell me anything. It's on a Mercedes OM603 (6 cylinder diesel) if that makes any difference.
You have to have the cylinder you are testing at exactly TDC for this to work. That way when the air pressure pushes down on the piston the connecting rod pushes straight down on the crankshaft and it can't rotate in either direction.
YMMV on a diseasal.
Introduce 80 psi of air and see how long it holds or what percentage of it leaks by. Some leakage is acceptable. If you hear hissing out of the tailpipe the exhaust valve leaks, hissing through the intake = bad intake valve and hissing at the oil filler tube indicates bad rtings.
Has to be top dead center on the compression stroke. That's the only time when both valves are closed and the air pressure won't turn the engine until one of the valves opens again.
Generally you can find this spot just by adding a small amount of air and watching the gauges. I add about 10 psi and then rotate the engine until you see the 2nd gauge hold most of that 10 psi. Then, i bump (not slowly turn, literally bump) the engine little by little. If the 2nd gauge bumps upwards, piston is going up, down is down etc. At some point the gauge's bumps will change direction, which lets you know you just passed TDC. So, as soon as the second gauge bumps in the other direction, back up a bit and crank it up to 100. That should be top dead center.
914Driver said:YMMV on a diseasal.
Introduce 80 psi of air and see how long it holds or what percentage of it leaks by. Some leakage is acceptable. If you hear hissing out of the tailpipe the exhaust valve leaks, hissing through the intake = bad intake valve and hissing at the oil filler tube indicates bad rtings.
First time I read RTINGS I read things.. Then realized it probably was supposed to be rings........ and then realized it doesn't matter.....both are true...
RINGS, yesterday was my secretary's day off.
Some engines have TDC markings for all cylinders on the flywheel or crank pulley. On my Formula Fords, I pull all the plugs so it is easy to turn and use a wooden pencil through the spark plug hole to find TDC. Not sure how many engines that would work for, though.
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