Generator issue

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Laura & Charles

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Could be anywhere. Originally from Ohio (Go Bucks!
I’ve not read about this particular issue on here and am wondering if anybody else has experienced this.
Onan 10KW Diesel

We had our generator PM service done last February while in Las Vegas. Did not have a need to start until we were well away from Vegas on our way back to Ohio. (Note to self: Start it up after service.) The first time we tried to start it after that service it ran for about 30 seconds and shut down. Tried a restart and it ran the second time for only about 10 seconds. The error code was a 3-6 which is too generic to mean much: engine stopped without command to do so. Issue certainly seemed to be fuel-related.

Finally got it into a Cummins shop and they called me today and said they had the same, 30 second run and shutdown. Said they held the prime for about a minute and started it again and it ran for 45 minutes and they shut it down. They’re going to check a few other things but said, given the PM service just prior to the onset of symptom, they suspect that the folks that did the PM service introduced air in the fuel system when they changed the fuel filter and that giving it an extra long prime purged the air.

1. Has anybody experienced this or heard of this as a thing?
2. Certainly seems like ‘holding the prime for a minute’ would not be a bad suggestion for routine genny issues that seem to be fuel-related.
 

Gary RV_Wizard

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Everything you described is consistent with lack of fuel or air in the fuel line, and that can happen when changing a filter. Hard to imagine they didn't start the genset after completing the service, but the techs are often in a hurry to get to the next job.

I've had my Onan QD 7500 be a bit slow to start after changing a filter, but it usually ran fine once it started.
 

John From Detroit

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I have indeed heard of it. never experienced it but don't have a big D just gassers.

There is one other possible issue but I would think 45 minutes run time would have found it. I"ve had that problem.
 

Laura & Charles

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Could be anywhere. Originally from Ohio (Go Bucks!
Thanks all! Yes, Gary, hard to imagine a tech wouldn’t have done a post-service test run but it appears to be the case. Nothing else was found and it now starts with the ‘normal’ length prime and runs until I shut it down.
(Isaac: Gary’s model number, of course, is correct.)
I’m glad it was a simple fix and glad to have gained the knowledge. Hoping the $$ I spent to learn it can help others here.
 

SargeW

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Just as an FYI, if it happens again it can be a symptom of a small leak in a fuel line admitting air into the system. Hopefully you are all fixed and no further issues.
 

Matt_C

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Mar 4, 2019
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SE - Mich
Laura and Charles,

Again with Gary.....
I am a ship's engineer by trade and needless to say have some diesel experience. The symptoms you described were very typical of an engine that was improperly purged of air after a service of any kind or being run out of fuel.
I suggest that you look in the owner's manual and read the section (it should have) about bleeding the air out of the fuel system. This is a situation that is so common in diesels that some actually have a placard on the engine that leads one through the procedure to bleed the fuel system of air.
Matt
 
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