Distributorless Control Module

Distributorless ignition systems have been around for almost a decade now, and have eliminated much of the maintenance that used to be associated with the ignition system. No distributor means there is no distributor cap or rotor to replace, and no troublesome vacuum or mechanical advance mechanisms to cause timing problems. Consequently, distributorless ignition systems are pretty reliable.

Even so, that does not mean they are trouble-free. Failures can and do occur for a variety of reasons. So knowing how to identify and diagnose common problems of these systems can save you a lot of guesswork the next time you encounter an engine that cranks but refuses to start, or one that runs but is missing or misfiring on one or more cylinders.

If an engine cranks but will not start, is it fuel, ignition or compression? Ignition is usually the easiest of the three to check because on most engines, all you have to do is pull off a plug wire and check for spark when the engine is cranked. On coil-over-plug distributorless ignition systems, there are no plug wires so you have to remove a coil and use a plug wire or adapter to check for a spark.

If there is no spark in one cylinder, try another. No spark in any cylinder would most likely indicate a failed distributorless controle module or crankshaft position sensor. Many engines that are equipped with electronic fuel injection also use the crankshaft position sensor signal to trigger the fuel injectors. So, if there is no spark and no injector activity, the problem is likely in the crank position sensor. No spark in only one cylinder or two cylinders that share a coil would tell you a coil has probably failed.