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Topic: Changing Fuel Pump on Onan Generator

Posted By: 1ed on 09/23/08 10:35pm

I have a Onan Marquis 7000 Model NHM Letter C and it will stop after about 16 minutes.
The oil is full
oil changed with new filter
Changed fuel filter
Full tank of gas
Air filter has been cleaned
One of the Techs at Onan said he thought it was the fuel pump.
Is there a way to check for that?
I have tried to call back but the line is busy or vm.
Also after I was crawling around under the MH I saw another fuel filter which I am going to change.
Has anyone ever changed the fuel pump if so I would appreciate any advise you may offer. Any ideas as to where to get the fuel filter part # 149-2267 Thanks ED


Posted By: pulsar on 09/24/08 01:55am

Moved from Technology Corner to Tech Issues.


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Posted By: 1ed on 09/25/08 10:28pm

Thanks for all the great information.
I checked with Onan and they want $268 for the pump and talked with the Truck Center that does work for me and they will put it on for about 2 hrs of labor and maybe less and they have a reasonable rate of $85 per hour.
After reviewing the location of the pump and they confinement of trying to get it out and then in again I think I will have the pros do it. Again, thanks for the input.


Posted By: gunny357 on 09/25/08 03:16pm

CloudDriver wrote:

I had a fuel pump failure on our 4kw Onan. The generator would run for 10-15 minutes then surge and shut down. After about 1/2 hour it would start and again run for only 10 minutes or so. The start switch at the generator has a prime function that runs the fuel pump without cranking the starter. I noticed that after the generator would shut down, there was no sound from the fuel pump on prime. Apparently, the pump was overheating and seizing up. If your 7kw model has a prime function, this test may verify the pump.


Good advice.

Easy, simple, cheap.

Thanks for sharing


Posted By: CloudDriver on 09/24/08 09:41pm

I had a fuel pump failure on our 4kw Onan. The generator would run for 10-15 minutes then surge and shut down. After about 1/2 hour it would start and again run for only 10 minutes or so. The start switch at the generator has a prime function that runs the fuel pump without cranking the starter. I noticed that after the generator would shut down, there was no sound from the fuel pump on prime. Apparently, the pump was overheating and seizing up. If your 7kw model has a prime function, this test may verify the pump.


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Posted By: texasrvr on 09/25/08 09:29pm

Have a Marquis 7500 and had same short run & surging problem. Tested fuel pump by disconnecting fuel line and attaching a short length of tubing and putting it into a fuel container (gas). If you move the fuel source higher then the carb and the engine starts & runs without surging or quitting and then move it below the engine (on the ground) and it begins to surge after a while that's a sign you have a fuel pump that can't pull fuel from the tank. Replace it.

Don't try to bypass it and use a automotive pump. Cheap way out. Auto pumps put out 5 to 8 psi and will screw up your carburetor. The pump used by Onan is made by Cummins and puts out approx. 3 lbs. psi and is designed to be a low pressure pump. This pump will run you approx. $350 and then it has to be installed. Charge varies depending on who does it. Get estimates from Camping world as a benchmark and go from there. They use a flat rate manual for labor charges.

If you are very handy it is a couple of hours spent in and under the coach and I can assure you it ain't fun. The pump is mounted by three bolts to a subframe on the genset and once you get these undone the pump drops down out of a access hole. Of course you have to disconnect wiring and tubing. Also make sure the batteries are disconnected to prevent any chance of a spark ocurring. The other half is getting the new one in and bolted down. Removal and replacement is not a job for the average owner. Space is very cramped and manipulating the pump around in the mounting area is pretty frustrating.

I did it and it all worked out but it was not fun.

A shop like Camping World will drop the genset out the bottom of the coach with specialized tools like a tranmission jack or something like that and work on it out of the coach which opens everything up.

I don't recommend this job unless you are really handy and have the time.

Take the MH to a Onan service center and as Larry the cable guy sez.. "Git er Done"


Posted By: 1ed on 09/26/08 10:24pm

Well it was a beautiful day and needed something to do so I thought I would take one more look at that fuel pump and I said I can do it so I did. Took that puppy off in about 45 minutes and the hardest part was trying to get it out of the hole in the bottom of the rack but I did it and ordered the parts and decided to get a new solenoid since I had that puppy out. I got the parts for Onan and the fuel pump was $268 and the solenoid was $108 but I saved the labor rate at the truck shop so I had a great day and saved $170.00 and have a great sense of satisfaction that I did it. Ed


Posted By: gunny357 on 09/27/08 07:27am

You can do even better on the price of the fuel pump. Get a low pressure one from an automotive source. They are out there and are under $50.00.


Posted By: texasrvr on 09/26/08 11:39am

Good move at $85 per hour. Most RV shops will nick you for anywhere between $115 to $135 per hour. Also a good price for the pump.

I have gone to a local Chevy dealer for running gear work at $85 per hour but their rates have gone up to $92 currently. So you are getting away with a good rate.

Glad you took a look and you saw what I was talking about.

BTW: A good move is to use a fuel stabilizer if your MH sits for any length of time. My rule is if I am not going anywhere for a month or so I dump in enough stabilizer (Stabile) for 80 gallons. One large bottle will be the right amount. Do this before pumping gas to mix it up and then run the engine and genset to make sure it has ended up in the genset carburetor and engine injectors and pumps.

Cheap preventative way of keeping it going....


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