Onan Problems

[Stretch]

After driving MH until the fuel gauge reads less than 1/4 tank, I park overnight without attempting to run the Onan. NExt day I refuel. Then try to start the Onan. It starts and runs for about 60 seconds and dies. It wont restart without a lot of priming.

OR
The MH has been parked for a week or two with a full tank. When I try to start the Onan it starts and then dies as in above. Lots of priming and it starts and runs well.

Obviously the Onan has lost its fuel prime but I cannot understand why. ANY IDEAS?

[Stretch]

After driving MH until the fuel gauge reads less than 1/4 tank, I park overnight without attempting to run the Onan. NExt day I refuel. Then try to start the Onan. It starts and runs for about 60 seconds and dies. It wont restart without a lot of priming.

OR
The MH has been parked for a week or two with a full tank. When I try to start the Onan it starts and then dies as in above. Lots of priming and it starts and runs well.

Obviously the Onan has lost its fuel prime but I cannot understand why. ANY IDEAS?

[troth]

Stretch, I'd be suspicious of a teeny air leak in the fuel line, especially where any rubber hoses are involved. Check your hose clamps & hoses; replace if they appear cracked on the ends or swollen.

[Stretch]

I will look at the fuel supply line to the Onan, for swelling or otherwise defective looking hose. However if the line has a pinhole that allows air in I dont think it will be visable because air is going in, and not fuel going out. Will let you know.

[rockcj]

at 1/4 tank, it will shut off. Try filling your tank. It is for safety.

David
05

[Fredbob]

Strech-- I have had the exact same problem in my 2000 fds 40 since day one. I rerouted the fuel lines twice with the thought that they might have too much drop when the nose is closed- didn't work. Tightened fittings at both ends of hoses--no difference. To be honest Ihave learned to live with it even tho it's a PIA. I also find it makes no difference if your tank is full, half full or just below a 1/4. If anyone out there has figured this problem out I would like to hear from them. Onan will give you a bunch of blank stares if you ask them. Sorry I couldn't help but at least you know you're not alone. Good post. --- fredbob

[rockcj]

I was told by Saddleback RV Service Manager about the 1/4 tank shut-off.


David

[Tom and Patty]

Mine shuts down at 1/2 a tank. It's worse if I'm going up hill or stop on an up hill. I still haven't had time to see if I can lower the pick-up point.

[Ted III]

You can reduce the pick-up point by reducing the length of the pickup tube. Don't ask me how you get it out.
Ted

[Fredbob]

I'm not quite sure where this thread is heading, but if you will reread the original missive by stretch you will see that it has nothing to do with the pickup tube in your fuel tank. The Onan in his and my case will start and run for 30-60 seconds and then stop. In reality it is running on just the amount of fuel that's captured in the hose and it loses prime and dies. You can get it started again, but it will take about 4-5 minutes of priming and restarting. As soon as it restarts it will run just fine for hours. Hope this will clear things up --thanks--fredbob

[Stretch]

right on fredbob. You understand exactly. If I push the prime side of the Onan switch for about 3 minutes it will finally start and run for hours.
I am going to check the hose leading to the Onan. My last motorhome was a 2000 Alpine. I had the same problem, in spades. I even added a check valve into the supply line. It did no good.

[Ted III]

As a pure novice, what type of fuel pump delivers the fuel to the generator. Is it mechanical or is it electrical. If it is mechanical, can it be changed to an electric pump? For whatever reason the unit is not getting fuel. I am not certain of all of the types but most of the diesel Onan generators have Kubota engines. Why not contact them directly or whosevers make it is. I have operated a repair shop for industrial equipment & overhead cranes for 45 years. Manufacturers are notoriously good people and usually way ahead in the problems that all you folks may be having. Sure is worth a phone call. If you can't locate someone to help, get in touch with me, trust me, I will find the correct individual
Ted Ulmer

[EngineerMike]

I'd guess same as Ted, fuel pump circuit. Could be faulty relay that isn't kicking on to power an electric pump, but that gets kicked closed during the long prime.