Re: 175 Merc EFI intermittent issues
Intermittent electrical problems can be the toughest ones to figure out if you do not go about troubleshooting in an orderly, systematic manner.
Remember, there is NO RETURN on electrical problems, do NOT order, buy, or replace ANY parts without first testing and PROVING that part defective.
Troubleshooting, testing must be done immediately, while the condition occurs.
If the motor is running fine, it is very difficult to determine an intermittent fault.
You will need an adjustable gap spark tester, a remote starter button is very helpful if you do not have a helper. A spark plug wrench will save wear and tear on the starter motor and battery. An inductive timing light can be very helpful also.
The moment the condition exhibits, leave the motor idling and use the inductive timing light to check each spark plug wire, if the timing light does NOT flash on any cyl's, write down which one(s). Now shut off the motor, use the adjustable spark gap tester and retest each plug wire for spark, verify a 7/16 inch spark to all cyl's, no spark to some. repost your findings.
If there is no spark to any cyl, you have identified an ignition/electrical problem, now you can further test to determine the source of that problem.
