Onan 4KW Microlite generator quits running

I have a 1997 Winnebago Adventurer with a KY series Onan. The RV is new to me. The dealer demonstrated the all the RV systems before I took delivery, and the generator was supposed to be freshly "remanufactured." It ran fine and produced power. The motor itself is clean and the oil is perfectly clear as if the motor has no significant run time, but the housing, carburetor, and some other stuff are obviously not freshly rebuilt.

The engine runs fine while it is running. It started without issue the first time for me about 2 weeks after I took delivery and I let it run about 15 minutes, but a couple of weeks after that, it had trouble starting. The starter appeared to be bad (chattering and grinding), however the generator did start after repeated tries (and ran good producing good AC power), but it quit after running for about 15 minutes, and it surged for several seconds as if running out of fuel as it quit. I did not try to start it again because of the starter issue. Later, I discovered the "starter problem" turned out to be a disconnected ground wire from the starter solenoid. I fixed that and another disconnected ground wire, then the motor cranked and ran good for between 10 and 30 minutes before it quit without me present to know when and if it surged before stalling. It was producing good AC power for at least 10 minutes, and it was running fine without any apparent problem. I tried to start it again at about 30 minutes after the initial start-and-run, but it only cranked without starting. Again, the starter issues is fixed, and it now cranks good. There was a load of about ~900 watts on the generator when it quit.

Any idea why this would happen? I suspect that if I try tomorrow, the generator will start and run for about 15 minutes, then quit again. The fuel pump and filter are old, but how could it run so good for 10+ minutes if they were not passing enough fuel? The motorhome has more than 1/2 tank of fuel according to the gage, and I recently added about 15 gallons to the 78 gallon tank. The gage did go up a bit with the added fuel, so I think it is fairly accurate. The coach is resting level in my flat driveway.

I have taken the gas cap off a couple of times, and there was pressure in the tank that took a while to relieve. Have any of you had this pressure push fuel past a bad generator fuel pump temporarily?

My next diagnostic check will be for fuel flow at the carburetor fuel line, as soon as I get the chance.

Is the generator offering any fault codes?

Here's a list of parts and the Onan manuals. Arm yourself with knowledge.  ;D

http://www.cumminsonanstore.com/

My Onan generator requires me to prime the fuel before starting. Ironically this is achieved by pressing down the remote STOP button for about 40 seconds, then the generator turns over pretty quickly when I switch to the start button. I let it rumble and mumble until it smooths out nicely, then I start adding the load to it.

Generators LIKE a load, don't just run it for the fun of it with no load on it. By load, I mean stuff like fridge, or fans or AC etc.  8)

Good luck and let us know what you find out.

I did not remove the fuel line and check flow, but I did connect 12V to the fuel pump, and it pumped fuel to the carb. It sounded like I expect a reciprocating pump to sound. Nothing happens at the fuel pump when the start switch is pushed to the "stop" position, and the owner's manual says nothing about priming the genset carb by holding it in the "stop" position. The fuel pump gets power when the switch is in the start position and when the motor is running. This is a KY genset; it has no diagnostic messages or codes that it displays.

I started the genset and left the compartment door to the generator open, thinking that maybe the hot air was recirculating and causing it to shut down from overheating. It ran fine and generated power (about 110V and 57 Hz) for 35 minutes, then suddenly quit generating AC power, but kept running. I had about 1700 watts of load on it when the AC power died. The circuit breaker at the genset did not trip. Any thoughts?

I am hating this generator!

Make sure the input fuel line to pump is good.The hose may be collapsing under suction.

OK folks, I think the generator motor will probably keep running if the MH is moving or the generator compartment door is open. I think that hot air recirculating under the MH causes the stalling problem, but I won't know for sure until I get the new generator problem solved (look for a new thread). I now get no voltage difference between the neutral wire from the genset at the automatic power switch and the "hot" (black) wire at the same location. I am getting full voltage between the line (black) and ground, but nothing to the neutral (white) wire.

Taking this new issue to a new thread...