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Author Topic: High Fuel Usage on Onan Diesel Generator  (Read 1875 times)

maryland-david

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High Fuel Usage on Onan Diesel Generator
« on: September 29, 2009, 07:36:57 PM »
I am looking for possible causes for high fuel usage on my Onan Diesel Generator. I am burning in excess of 1.5 gallons per hour on my 10KW unit. I should be burning about n.5 gallons per hour on half load. My generator has 5000 hours on it. I pulled off the top and front covers today to check the generator end bearing as I have been told that when they start to go, the generator works real hard and will consume allot of fuel. The bearing looks good. I also cleaned out the spark arrestor and ran it an hour or so. Since it starts right up and I do not have excessive crank time, I am thinking that the valve adjustments are fine but may be an injector issue. Does anyone know if there are adjustments on these Onan Diesels injectors? By the way mine has an Isuzu motor. I appreciate any opinions. 
David
Baltimore, MD
2003 American Heritage 45'
500 Cummins
6 Speed Allison

KIX

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Re: High Fuel Usage on Onan Diesel Generator
« Reply #1 on: September 29, 2009, 08:43:12 PM »
I also cleaned out the spark arrestor

I assume you mean the air filter.   I am not aware of any adjustment that can be done in the field on an injector.  If it were me I would change the air filter AND the fuel filter.  If that does not improve your fuel consumption then I would change the injectors.

Please post your resolution
KIX

2002 Winnebago U/A 40J
Cummins ISC - Spartan
2013 Jeep JKUR

maryland-david

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Re: High Fuel Usage on Onan Diesel Generator
« Reply #2 on: September 30, 2009, 07:48:54 AM »
No, by "spark arrestor" I do not mean air cleaner. There is a plug on the side of the spark arrestor mufflers on these units and they need to be removed and ran at full load from time to time to clean them out. These mufflers do get clogged and can cause poor perfomance by increasding the back pressure. I believe there is adjustment on the nozzles so I will try that before replacing them. I regularly put injector cleaner in my fuel so I would assume that they are not dirty, but who knows.
David
Baltimore, MD
2003 American Heritage 45'
500 Cummins
6 Speed Allison

Gary RV Roamer

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Re: High Fuel Usage on Onan Diesel Generator
« Reply #3 on: September 30, 2009, 10:22:19 AM »
I wasn't aware a diesel genset had a spark arrestor in the exhaust. Gas, yes, but diesel?  But there it is, right in the service literature. I learned something new today [once again].
Gary
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Gary Brinck
2004 American Tradition
2007 GMC Acadia
Homebase: Ocala National Forest, FL

maryland-david

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Re: High Fuel Usage on Onan Diesel Generator
« Reply #4 on: September 30, 2009, 11:08:03 AM »
Indeed they have one and quite frankly in my opinion more important to clean out regularly than in a gas unit because of the soot that diesels, particularly older diesels produce. The literature says to run it for about 5 minutes under full load. Most techs that I know suggest running for one hour under full load to really clean it out.
David
Baltimore, MD
2003 American Heritage 45'
500 Cummins
6 Speed Allison

Marsha/CA

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Re: High Fuel Usage on Onan Diesel Generator
« Reply #5 on: September 30, 2009, 07:49:45 PM »
I can personally attest to the fact that the diesel generators have spark arrestors.   Tim (hubby) cleaned the spark arrestor on our 7.5 Onan generator a while back.  After he was finished he wiggled himself out from under the coach with a face all covered with black soot.!

Marsha~
Allegro Bus Diesel Pusher with Hyundai Tucson SUV toad. 
In case of necessity, alternate transportation is available in the form of 1 old horse.

maryland-david

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Re: High Fuel Usage on Onan Diesel Generator
« Reply #6 on: October 05, 2009, 02:07:58 PM »
Oh I knew better than to be underneath it when I started it! FYI as a follow up, I cleaned the spark assestor and changed the fuel filter. Ran the generator for 16 hours and my fuel consumption rate went way down. It was where I expected it at about 1/2 load. 3/4 gallon per hour. mine is a 3 cylinder Onan diesel that has an Izusu motor.
David
Baltimore, MD
2003 American Heritage 45'
500 Cummins
6 Speed Allison