Onan Generator Problems

[Adrian]

Hi All,
I'm a new clipper owner; 1977 on a MB300 chassis with a 440, and (original) Onan 4k generator.

Today I took the clipper out on its first shake-down drive.  Every thing was working great. We had the generator going, roof air on, driving down the highway. After about 25 min. the generator stopped. I haven't been able to start it since. I checked the obvious, oil level and it was OK.
I got the generator to run for a few seconds, but it would cut out after that.

I'm at a loss; the night before we ran it for over and hour with no problems.
Thanks

[handyman]

Adrain check for fuel the gen has it's own fuel pump easy way to find out spray a little starting fluid in carb and see it starts if so you might have a pluggeg fuel fillter or the fuel pump esent working if you have a elec pump for the engine it should pump to the gen also good luck  

[Adrian]

The saga continues;
Ok I let the generator sit overnight. Then this afternoon I started it with no problem and ran it for about 35 min., thinking it might be the float in the carb that was bad. However, it did not stall or flood out. Then I thought it maybe the fuel pump, because the generator seemed to stop when going up hill. I stopped the generator while hot let it sit for about 5 min (trying to create a vapor lock situation). The darn thing started right up??
It seems that I have to be traveling up hill (with the family on a hot day) to make it shut off (stall).
I took Jim's suggestions but the generator runs great on level ground. There is no problem with fuel delivery.
I talked to a friend and he said that it maybe the fuel level in the bowl. He suggested that I bend the tab on the float to lower the fuel level. He thinks it is flooding when going up hill.

Has anyone else had this problem or other suggestions?    
Thanks
Adrian

[handyman]

Adrian Jim again unless it starts smoking it's not flooding out if anything I would say it's starving for fuel you never said if you had elec fuel pump so start here replace your fuel filter then get a elec pump what I think your getting is when your going up hill the engine is demanding all the fuel and the gen dosent get enoff if your filter is buy the tank and it's plugged this will happen good luck  

[Adrian]

Jim,
Sorry in my long winded reply I failed to state that I'm pretty sure that I have an electric fuel pump. The fuel line goes in to a device labeled Onan, with a hot wire connecting it to what looks like a relay, then a steel line to the carb. It also looks like there is a solenoid just before the pump (is this necessary?). Also I traced the fuel line No Fuel Filter.  (Do you have any suggestions on what type I can use)
Thanks
Adrian

[handyman]

you can use any kind of in line filter just make sure you put it between the tank and the pump

[Adrian]

Thanks Jim,
Tried the starting fluid it generator started right up. You were correct it is a fuel starvation problem. I also checked the fuel line for blockages (none). I suspect the problem is with the fuel pump or some interrupt. I'm going to order the service manual for the generator.

[Conrad]

Why  would one want to have the generator running when you are driving around?  I don't have a gen but thought I would ask.  Power for refer?

[Adrian]

With the generator going you can run your roof air; this is a real necessity in the southwest.

[junebob]

Adrian, member #138- Generator problem. THE ONAN UNITS HAVE THEIR OWN FUEL PUMP. Two very common problems in the Onan ,[and probably othergenerators].Are caused by Old age and little use. The filter screen in the fuel pump gets plugged or partually plugged from debri in the gas over time., And the rubber in the pump deterates over time from old gas ,and the use of alcohol gas additives.This rubber can clog the jets in the carb. I suggest you take your unit to an Onan/Thermo King dealer shop. They can quickly   Clean out the screen and check the fuel pump for rubber debri and/or replace it.  Then they can try to clear the carb jets.If it works and stays unplugged fine.If not they can replace the carb. Most people think when they buy a twenty + year old motor home that has a generator with very few hours on the engine running time meter. That it's a good thing. Very often it's exactly the opposite. More running time indicates self cleaning and less gummy deposits from old gas thus less detereoraton . Once your system is repaired and up and running. install a in line shut off valve. When your generator is not being used for any long period of time. Shut off the valve while your unit is running . The unit running dry on gas and stopping insures you of an empty and clean fuel system. Good Luck, Bob Chaney #2626  

[Adrian]

Thanks for all the comments and suggestions.
We took our clipper out for its first camping trip. At the site I had time to look over all the suggestions you all have made. It looks like indeed my fuel pump has problems and my starter relay is toast.
Two questions:
1.Where can I get a new relay? Onan says that the relay for the 4.0 BF model generators has been discontinued. I tried a ford starter relay but it has the wrong polarity for the start pole.
2.Where can I get a rebuild kit for the fuel pump?

Thanks
Adrian
 

[Adrian]

Ok I went down to the Onan parts dept. today and took the actual starter relay. Apparently what is listed in the computer and the actual part was different.
So I was able to get a replacement starter relay. (they gave me the starter relay free of charge).
As for the fuel pump rebuild kit. There is none, they said that my only option was a new one. Before buying one they suggested I take the bottom housing off and clean the pump with carb cleaner, and also remove the fuel solenoid; that should solve the problems.
 

[Mark Smith]

Adrian,  
I read all the suggestion above, but there is one more thing I haven't heard mentioned yet that may have an influence on your problem. That is, the onan gen. is fueled from the clipper fuel tank. The generator pickup tube in the fuel tank does not go to the bottom of the tank. That is so the gen. will not use all of the gas in the tank and you will still have fuel in your tank to drive home.  If you are going up hill and your fuel tank is low, you may be lifting the pickup tube out of the gasoline. Keep your fuel tank full and drive up hills and see if it makes a difference. You may want to look at the pickup tube and bend it to go lower in the tank. Good luck
Mark ACOC#1077

[normy]

If you have a factory installed unit the engine and gen set use seperate fuel lines when the gen set runs out of gas you will still have about 8 or 10 gallons left so you won't be stranded