A diesel compression test is an extremely important engine diagnostic procedure. It should be done on any diesel you are planning to purchase. More than any other test, it can tell you if you are purchasing a healthy engine. The test should also be done anytime you are experiencing engine performance problems. Low compression can cause hard starting in cold weather, loss of power, rough idling and shaking, excessive exhaust smoke and poor fuel economy.
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When a diesel engine begins to lose compression it is a likely sign that it may be coming to the end of its life. If the compression loss is constant over all cylinders it is a pretty good indication that the piston rings and/or cylinder walls are worn beyond acceptable limits. In this case, only a complete and very expensive engine overhaul will fix the problem. In the case of compression loss over just one or two cylinders you may be fortunate enough to just have to replace a head gasket and/or grind your valves.
This guide will take you step by step through the process of how to do a compression test on your 615, 616, or 617 diesel engine, how to analyze the results, and how to determine where the problem might be. Manual is printed in 8.5x11 format and bound with a smudge resistant cover.
We have also had so many requests for compression testers, that we now offer a compact and reliable tester.