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I would like to ask you a question about a problem with my car. How can you tell if a car needs a timing chain before it fails? And does the car need to be running to put it on a diagnostic machine? James, Berwyn, Ill.

James, You can tell if a car needs a timing chain by doing certain tests before you tear it apart. Most of these tests require equipment that most auto hobbyists may not have. Here are some of the tests that you can have a shop perform to answer your questions. If you have a car with a distributor seeing how many degrees of "play" you have in the crankshaft BEFORE the distributor rotor moves. This will tell how much play a timing chain has. If it has less than 20 Degrees of play then the timing chain is okay. Another test that can be performed will require the engine to be running. And an ignition scope or lab scope is needed. On an engine without a distributor “look” at the signals of the cam and crank sensor with a lab scope while the engine is cranking is another way to determine if a timing chain has slipped or has more play than it should. The technician with the lab scope can show you what a good pattern looks like and then show you what your pattern looks like. And NO, a car does not need to be running to be put on a diagnostic machine. The best diagnostic machines I have, are my technicians. They diagnose cars everydays that are not running.


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