On Feb 13, 2018, at 12:21 PM, Deb McWade wrote:

> Have checked the board and it checks out (jumped the appropriate pins) per Jim K. It cranks but doesn't catch. Used to spark, and catch but wouldn't run more than 2 seconds.


Hi Deb, what you are describing is a classic symptom with just a few possible causes.

1. Low oil in crankcase causing low oil pressure condition. I believe you've already checked the oil level.
2. Low Oil Pressure Switch problem as others have pointed out.
3. Control board problem (likely)
4. Flywheel alternator problem (very UNlikely)

You didn't mention which pins you jumpered so it is difficult to advise further.

Under normal circumstances the control board watches for the engine to achieve a certain speed in a certain amount of time after cranking starts - once it sees that condition it de-energizes the starter and "latches on" the fuel pump and ignition system which thus allows the engine to continue running indefinitely. The "certain speed" portion mentioned earlier cannot be reached on the starter alone - the engine has to successfully start before it can be achieved. You've already said that it will run for a couple of seconds and then quit - therefore your ignition and fuel delivery is working.

If there's a problem with either the oil pressure system or the control board then this "latched on" condition does not occur and the engine stops after a couple seconds just as you described.

Once you are able to work on your coach again please follow the troubleshooting steps available on the GMCnet archives. The _very first_ one you should try is the "jumper 5 to 9" (or the equivalent: jumper battery+ to coil+) and then attempt a start. If it runs correctly then you can immediately start working on finding out which problem 1-4 above is the cause.

I completely concur with everyone who advised against taking it to a Cummins shop - you DON'T want to do that. You need the old-school engine shop who serviced this type of engine in the 70's and 80's and JimK can provide all the parts your shop would need. A good test for your candidate shop would be to ask the oldest mechanic if he has worked on breaker-point ignitions - if he says "no" then leave immediately.


Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH




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