How to diagnose a “No-Start” Condition on a Mercruiser 3.0L Marine Engine
Thursday, December 5th, 2013Question: My Mercruiser 3.0L Marine Engine will crank over but won’t start. Is there an easy place to start when trying to diagnose this problem?
Answer: There are 3 basic fundamentals with the operation of an internal combustion engine
- Spark
- Fuel
- Timing
As illustrated in the short video below it is very easy to verify if the engine is in fact getting the required spark at the distributor, and subsequently each cylinder. We like to use a standard engine timing light while connecting it to the main coil wire lead in between the coil and distributor cap. Once you have the timing light connected you can crank the engine over and visually verify if spark is being supplied from the coil to the distributor. In the event that you do have spark we typically go ahead and verify that each individual cylinder is also getting spark. This basically eliminates the distributor cap as a potential problem item as well.
If you do not see that the coil is providing spark to the distributor cap it can either be the coil itself or possibly the engine control module. At this point you can either test or in some cases the coils are relatively cheap and its easier to just take your chances and replace the coil.