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Author Topic: 1992 Onan 4000 dies  (Read 319 times)

B737doc

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  • Posts: 49
  • 1992 Challenger
1992 Onan 4000 dies
« on: August 25, 2017, 04:59:58 PM »
   I removed the little carburetor and thoroughly cleaned all the jets, checked float, etc, and reinstalled.  Runs really good for about 20 minutes (under load), and it starts "surging", then eventually dies. Any ideas???
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

Sloop

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  • Posts: 264
Re: 1992 Onan 4000 dies
« Reply #1 on: August 25, 2017, 06:14:10 PM »
Sounds like the classic fuel line from the tank to the generator fuel pump degradation.  It gets stiff, experiences small cracks, sucks air and starves the carb.  Might try a temporary line from a gas can to the fuel pump to verify.
1992 24' Fleetwood Class "C" Jamboree Rallye
Ford E350 Chassis
Toad - 1969 Volkswagen Baja Bug
San Marcos, CA

B737doc

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  • Posts: 49
  • 1992 Challenger
Re: 1992 Onan 4000 dies
« Reply #2 on: August 25, 2017, 06:29:46 PM »
Okay,  I'll replace it,  I figured it was either fuel or fire!  Thanks! 
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

cgmartin

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  • Posts: 533
Re: 1992 Onan 4000 dies
« Reply #3 on: August 26, 2017, 03:22:15 AM »
I have been doing some extensive reading on this forum, as well as any other source I can get my hands on, on the problems with surging and shutting down of Onan generators, and it seems that a lot of folks seems to be experiencing similar issues recently. While not all shutdowns and surging events  share the same symptons and diagnosis, one common theme that they seem to share is heat and or vapor lock, however, these latter causes have not been guaranteed as  definitely  being the culprits.  Do a search here and you will find many suggestions for curing this, but so far, I have not heard of a magic bullet for what ails a great number of Onan generators. In my case, I replaced the fuel filter, air filter, all rubber fuel lines, and moved the fuel pump outside and away from the generator.  I am still waiting to see if the problem has gone away. During you research, you will find suggestions which range from the low oil sensor, float sticking in the carburetor, dirty carburetor, dirty air filter, low oil level, etc.  One common theme is that those owners who have experienced the shut downs and what they believe to be vapor lock, are mostly living in extremely hot sections of the country, like Arizona. I have yet to hear this happening in winter, in Montana, or similar climates, but I could be wrong.

Ernie n Tara

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  • Posts: 3230
  • Life is Good - Together
Re: 1992 Onan 4000 dies
« Reply #4 on: August 26, 2017, 08:38:56 AM »
When I had a generator in the back (gas rig) I encountered the leaking hose problem and after fixing that found that dust in the generator compartment could cause the same symptom. Blew it out with air and it cured the problem.

Ernie
Ernie 'n Tara

2011 Winn Journey 34y
2012 Jeep Rubicon - Dozer (orange - kinda)
2006 Jeep Wrangler

B737doc

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  • Posts: 49
  • 1992 Challenger
Re: 1992 Onan 4000 dies
« Reply #5 on: August 26, 2017, 02:12:03 PM »
   She started and ran very nice this morning, this time running nearly an hour but was again attacked by the surge monster and died.  Crawled underneath, fuel feed line pliable with no leaks, cracks, or rotting anywhere. 
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

cgmartin

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  • Posts: 533
Re: 1992 Onan 4000 dies
« Reply #6 on: August 27, 2017, 02:24:47 AM »
What were the weather conditions like in the morning when it started? Was it relatively cool? Let it rest overnight, then start it the next day, in the after noon, when it is hot and muggy, and if my theory is correct, I think your generator will start okay, but may only last half the time before the surging returns and it dies.

gstreet

  • Posts: 1
Re: 1992 Onan 4000 dies
« Reply #7 on: August 30, 2017, 07:49:32 PM »
I have a 1996 onan mircroquiet 4000.  I was having problems with it shutting down in hot weather.  I took it to Cummins and Camping world and the techs checked it said it was working fine.  After reviewing comments on this forum indicating that others with the same problem have had success with replacing the fuel pump, I replaced the fuel pump and filter.  Problem solved.  I am surprised Cummins/Onan does not have better guidance on this issue.  I have built a small stand to hold open the exterior door to improve ventilation but not sure if that was necessary.  Thanks forum!

Willandgiselarv

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  • Posts: 87
Re: 1992 Onan 4000 dies
« Reply #8 on: August 30, 2017, 08:09:39 PM »
I have a friend with a 5th wheel and the Onan 4000 ....whenever it had problems running it was always the fuel pump, hose or carb.
Most of the time it was the carb, sometime cleaning them doesn't work and requires a carb replacement.
2004 GB. Bellagio 38ft  3126E Allison 3060
2015 Jeep Cherokee Trailhawk

B737doc

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  • Posts: 49
  • 1992 Challenger
Re: 1992 Onan 4000 dies
« Reply #9 on: September 02, 2017, 04:40:55 PM »
   Seems to be running lean.... tried to adjust mixture screw on carb, no effect..Set continues to run with no ill effects with the mixture screw completely removed...STRANGE
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

B737doc

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  • Posts: 49
  • 1992 Challenger
Re: 1992 Onan 4000 dies
« Reply #10 on: September 05, 2017, 02:51:02 PM »
Removed valve cover, set intake valve to .010, exhaust valve to .012.  Runs flawless under full load for 5+ hours.  Switched unit off, good to go.
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

 

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