My Onan 4kw generator has been making a clack, clack, clack noise since I purchased my motorhome in Jan, 2011. I didn't realize what a problem this was until the generator started cutting off after a while.So now I'm on a 1.5 month tour of the western US and it's important for the generator to work well and it keeps cutting off. Sometimes very difficult to restart and only staying on for a few minutes to hours.So I stopped by Onan in Nashville and talked to a technician there who said it was probably the fuel pump. He didn't have time to repair it but made an appointment for me in Oklahoma City. The tech in Oklahoma City replaced the fuel pump and the fuel filter but the clacking noise continued. The tech told me that it was probably the fuel line and that the noise indicated that the fuel pump was sucking air. The pump was covered under warranty, but the overtime and travel wasn't so it cost me $450.00 and no fix.Then I scheduled an appointment at Ford in Phoenix to check the fuel line on my 2010 F53 Chassis. They dropped the fuel tank and removed the fuel pickup assembly and inspected all the connections in the fuel line and did a smoke test and blew compressed air through the lines. They found nothing wrong with the fuel line. That appointment cost me $600 and no fix.So now I've spent $1,100 and still have a malfunctioning generator. My next step, if I can find a good mechanic, would be to isolate the fuel system from the generator by bypassing the fuel lines and hooking up a short hose from the fuel pump to a bladder of gasoline. Does anyone have any ideas what else I can do to fix this thing? I'm in the Grand Canyon area now heading north through Salt Lake City, then Yellowstone in the next few weeks.

Never heard of a fuel pump make a clacking noise. Low oil and valves/rods maybe. And didn't the guy who installed the fuel pump notice the noise was still there? Another thought,check the choke.It might have a broken rod and it's opening/closing and making that noise.And it will make the gen shut off. Good luck.

Well if it is a metal to metal clicking noise could be anything inside the engine from rods to valves, low oil pressure etc. Impossible to tell without listening to it but if two Onan mechanics agree it has to do with the fuel they should have stayed with it until the problem is resolved.I suspect they know you are on the road and the easiest way to deal with it is to send you somewhere else it's no fun pulling the generator.

Helpful siteThis site might provide some help. Using a separate fuel supply is an excellent way to isolate the issue. It could be as simple as a loose hose clamp. Mine was. If the clacking noise is the fuel pump it might indeed be sucking air or have a faulty pick up tube. If the clacking stops with the external fuel supply it would be because the fuel bowl float has cut the incoming fuel off until it needs more. I don't think it shuts the pump off it is just the design of the thing that makes it go quiet when up against pressure. Since the pump was changed it is unlikely the issue. I would do my best to connect a new piece of hose directly to the fuel pump input and bypass all existing hose lines. I once found with great difficulty, some silicon sealer floating in one of my boat fuel tanks. It would float around and cover the screen in the pickup tube at the bottom of the tank. Under heavy throttle the fuel demand would suck the little flap tight and the engine would stall. I could idle all day long. My second tank never gave me a problem. It might be possible that your fuel tank is not venting and the generator just can't suck the fuel up when the tank has a vacuum built up. Acts like a vapor lock. On my 89 Ford as many many others have found on Fords the internal fuel tank caused a lot of grief for the main engine. Your symptoms may vary with different levels of fuel in the tank, outside temps, or climbing a hill on a hot day. My new mh in 08 has an 8KW Onan diesel generator that gave me fits. Similar symptoms. When the fuel tank was full it ran fine. The hose on top of the tank pickup tube was never tightened from the factory. It would idle nice, run most of the time, but under heavy loads it would act like it was starving for fuel, which it was. It would prime again (clack clack clack) and start right up. A few turns from a nut driver solved the issue.

(I got get quicker typing, above post is what I was going to say with URL that gets manual.) Also had another thought. Inspect the motor mounts, maybe they came loose. They are just a bolt with rubber on them.

I also have a 2011 Fleetwood Storm that has Generator issues. The generator shuts off without warning continuosly. I had it in the shop several times without success. But on a recent trip to Florida the generator shut off every 17 mins without fail. We were frustrated with no AC and 100 degrees outside. A tech in Lake City, Florida (North Florida Welding-highly recommend this shop) tried changing the fuel filter, fuel pump, and fuel line but it did not help. In my case the generator ran fine when sitting still, but died when we drove. The tech from florida called fleetwood repeatedly until he received a reply. A Fleetwood tech returned his call and stated the issue is a design flaw that causes the hot air from the engine to be sucked into the generator causing the unit to overheat. No remedy has been offered for it, so I am stuck with a RV that I can't travel in, and a generator that has overheated numerous times.Another issue is oil collecting in the air filter. Onan has a kit to repair that under warranty.

Generator Clacking | Good Sam Community

C-Leigh_Racing
Explorer
Jul 05, 2013
Storm, tell me more about this oil hole, because my air filters getting oiled.
Thanks, Neil
Stormdriver
Explorer
Jul 04, 2013
Fleetwood did a recall or design edit so to speak. They box in the generator and extend the exhaust pipe. Had this done by dealer at no cost but it did help. May be too late for our generator. It overheated several times.
Onan also has a recall for the generator itself. The oil return "hole" is too small so oil does not drain quickly enough. They drill a larger hole and the problem of oil clogging my air filter went away.
holstein13
Explorer
Apr 17, 2013
I wanted to update everyone on this problem.

Today, I picked up the MH because I've got a camping trip planned for Friday. They completed two thirds of the fix. The fix consists of three things. 1) A recirculating fuel line that creates a loop where the fuel can condense and remain a liquid to prevent vapor lock, 2) A heat shield to prevent engine heat from heating the generator and line too much and 3) a re-route of the existing exhaust from under the fuel pump to the back of the motorhome.

They did #1 and #2 but they didn't have the tail pipe to complete #3. On the way home today, I didn't notice any clacking sound but will give this a full test on Friday. Wish me luck.
holstein13
Explorer
Apr 03, 2013
MustangGT wrote:
I haven't read this whole thread, but since the overheating happens when the RV is moving, try adding a sheet metal deflector or two to channel air where you need it or hot air away from where you don't. Maybe a small weather-resistant 12v fan too? A low cost, low effort possible fix.

I believe that is part of Fleetwood's fix. I'll keep you posted.
MustangGT
Explorer
Apr 03, 2013
I haven't read this whole thread, but since the overheating happens when the RV is moving, try adding a sheet metal deflector or two to channel air where you need it or hot air away from where you don't. Maybe a small weather-resistant 12v fan too? A low cost, low effort possible fix.
holstein13
Explorer
Apr 02, 2013
What a timely post. I have an update to report. After extensive investigation, Fleetwood has come up with a fix for this problem. It consists of two separate fixes.

1) They are re-routing the exhaust to the back of the motorhome to help keep the generator cool. This is such an obvious thing that I'm surprised they put it in this way to begin with. A closed door blocking the generator right behind the chasis engine is bound to get hot so re-routing the exhaust will clearly help.

2) They are installing some sort of device to prevent vapor lock. From the way they described it, it is some sort of T-valve that allows liquid fuel to continuously cool the fuel near the carburator and prevent the gasoline from vaporizing. Even if it does vaporize, the continuous flow of fuel should prevent the carburator from sucking dry. I am having a hard time understanding how this device will work but will hopefully see it installed soon.

I will keep you all posted when I get the coach back from the dealer in a few days.
FuelFunnel
Explorer
Apr 02, 2013
Pathflyer wrote:
I know this is old.. but have to reply..

I have a Onan Marquis 5000 generator in my 97 Pace Arrow 35' Class A. Three years we took a summer trip from Houston To Balmorea State Park almost to El Paso. IT WAS 100+ F outside. The generator worked great until we got in the desert heat and it would run for 15 minutes or so then just shut off.
I would restart it.. which took some time to do and get another 15 minutes out of it. After Fort Stockton I finally just pulled into a parking lot and decided that the generator was overheating.. or causing vapor lock in the line from the heat and took the outside door from the motorhome. PROBLEM SOLVED. It continued to run non stop for the rest of our trip. Unfortunately the way the hinge works. I have been unable to actually reinstall the door correctly LOL When I open it the door just comes off in my hands now. I installed some dowel pins in the top to keep it installed. Over this weekend we were coming home from east texas in the RV and it started to rain.. I pulled over and put the door on. It ran normally for about an hour then went back to the old shutting down issue. I let it sit for 10 minutes.. took the door off again and it worked flawlessly for the rest of the trip. The heat inside the generator enclosure is overheating something...??? I own an automotive garage and love working on cars and even my motorome... so last year I installed an CHT gauge for both of my generator cylinders. I see about 200F CHT running normally or about 220F loaded. Door closed or open.. engine temperatures are the same.
I am seriously going to install several vents in the generator door and am even considering installing a small fan to suck the hot air out of the top. IDEAS??? THOUGHTS??

Possibly plumb and re-wire the fuel pump to the exterior of the generator compartment. Vapor lock typically happens on the suction side of the pump & fuel line, so if you can isolate that half from the heat, it may help.

Kris
Pathflyer
Explorer
Apr 02, 2013
I know this is old.. but have to reply..

I have a Onan Marquis 5000 generator in my 97 Pace Arrow 35' Class A. Three years we took a summer trip from Houston To Balmorea State Park almost to El Paso. IT WAS 100+ F outside. The generator worked great until we got in the desert heat and it would run for 15 minutes or so then just shut off.
I would restart it.. which took some time to do and get another 15 minutes out of it. After Fort Stockton I finally just pulled into a parking lot and decided that the generator was overheating.. or causing vapor lock in the line from the heat and took the outside door from the motorhome. PROBLEM SOLVED. It continued to run non stop for the rest of our trip. Unfortunately the way the hinge works. I have been unable to actually reinstall the door correctly LOL When I open it the door just comes off in my hands now. I installed some dowel pins in the top to keep it installed. Over this weekend we were coming home from east texas in the RV and it started to rain.. I pulled over and put the door on. It ran normally for about an hour then went back to the old shutting down issue. I let it sit for 10 minutes.. took the door off again and it worked flawlessly for the rest of the trip. The heat inside the generator enclosure is overheating something...??? I own an automotive garage and love working on cars and even my motorome... so last year I installed an CHT gauge for both of my generator cylinders. I see about 200F CHT running normally or about 220F loaded. Door closed or open.. engine temperatures are the same.
I am seriously going to install several vents in the generator door and am even considering installing a small fan to suck the hot air out of the top. IDEAS??? THOUGHTS??
rgatijnet1
Explorer III
Oct 25, 2012
Look underneath the generator and see if you have a broken weld in the support frame. That is the problem I had with my Monaco coach.
Ron8877
Explorer
Oct 25, 2012
It is a electrical part and sometimes they are bad when new.
Ron

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