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My compression tester won't hold the pressure after I stop cranking the engine. Is the gauge defective?
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Staff
replied three years ago
The compression tester is a simple pressure gauge. If you connect it to your shop air supply, does it correctly read the system pressure? If so, then the gauge itself is perfectly fine. There is a Schrader valve in the end of the adapter hose that retains the test pressure, and occasionally it can get contaminated with some carbon or other debris from the engine under test. If this happens, then the valve will not seal, and the gauge will not hold pressure. The valve is located in the end of the adapter hose, inside the spark plug adapter end. Use a standard valve core tool to remove the valve, clean it with some cleaner, and replace it. The tester should work normally then. If the valve is damaged, it can be replaced with a standard Schrader valve.