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.
"If momma not happy ....Who cares.I have my TH AND my toys .
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.
Garry1p
1990 Holiday Rambler Aluma Lite XL
454 on P-30 Chassis
1999 Jeep Cherokee sport
This 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.
* This post was
edited 07/12/12 11:28am by path1 *
(To cheap to buy new)
1990 37 ft 5th wheel that hasn't moved since 1996 (our best home)
1997 33 ft trailer (winter home in much warmer climate)
2005 25 ft M/H (our "stand up B" for traveling)
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.
Get a gas can and use that for a temp tank. Buy some rubber tubing at the parts store. Remove the fuel pickup side of the Fuel Pump and replace it with a tube that goes to the gas can.
This is just temporary so any rubber tubing will be ok for this.
Once you prove/isolate then rehook up the original gas lines.
A clacking noise is usually internal engine issues which could get worse when hot and cause the enging to quit.
You need to get written estimates on the clacking noise and what ever else it is doing. If the estimate say fuel pump, then you have recourse. I would not have paid the bill for the FP until the clacking noise was repaired.
MikeD
91 Holiday Rambler Imperial 37
F460 G-hog
Toad: 2up Toyota
Northern Illinois Our Travels and Tips Blog
My biggest issue is the generator has been abused due to the design issue. Running under those conditions so many times makes me wonder if the unit will last very long. Overheating can warp valves and damage seals...etc.
From what I've been reading, theres quite a few of us going through this same problem, genset cutting off while going down the highway or once we stop while traveling for a short break.
It could very well be a heat issue causing the problem, because on ours in cool or cold weather, we never have a problem.
Now on holstein genset, it being a 2011 unit & 4000kw, I dont really know that type of engine, but I'm thinking it may be one with overhead valves & rocker arm, so holstein will need to check that & let us know.
On the other gensets, like say the 5.5 or 6.5kw, those engines are the type I call the old L head opposed cylinder twin, where the valves are in the block & just a flat head bolted on.
That design of engine, where the valves are located in the top part of the block & head is flat over top of the piston, its not uncommon for carbon to build up on the flat of the head & top of the piston & after a while the carbon will get thick enough, the carbon surfaces will start to contact each other & result in a knock or clack.
Briggs & Stratton, had an opposed twin cylinder mower engine just like the Onan & was recommended by Briggs to remove the heads & clean the carbon off the head & piston every 100 hours.
The Onan being of just about the same design as that Briggs, I would think would fall into the same type of cleaning process to prevent the knock or clack from the engine.
I can tell you this much, I have an old 18HP twin Briggs mower engine I bought back in the early 80s & a few years back came a slite knock in it & I just let it go. That knock got louder untill it sounded like it was going to blow up, so when I pulled the engine apart, one of the rods the rod bolts were backed out & that resulted from the carbon build up & it couldnt be compressed any further so something had to give up.
Seeing as I have heard, what an electric fuel pump sounds like before it is filled with fuel, would create a kind of light tin like clack if no fuel was in the pump, were as a carbon build up on the head & piston would cause a more deeper & louder type clack or knock.
As far as both those repairs that was made on holsteins genset, that could be chocked up to a lesson learned from it for him or either a letter sent to those repair places & a refund asked for, because all they did was take his money & the problem not corrected.
We RV folks, seem to be sitting ducks for places like that out on the highways, its just unbelievable how crooked they can be.
Neil
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....Who cares.I have my TH AND my toys 
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