Onan 4000 4KYFA26100, starts runs about 10 minutes then shuts down

[Mtutton]

I have a 1996 Onan 4000, model 4KYFA26100.  It?s mounted in a 1996 Fleetwood Tioga Montero Class C.  The generator  has 247 hours on it. When it runs, the choke opens as it should, power output no load is 120-125 volts. Tank is 3/4 full, fuel flow is present after the generator quits, tested spark, it only sparks when I release the start switch. Carburetor is clean, new magneto, new solenoid, new carburetor, oil switch disconnected, new fuel filter.  I have run through all the troubleshooting guides. I have the service manual. I have put a direct pick up tube in a gas can and run the generator, same thing happens.  Runs smooth for 10-15 minutes, cuts off, won?t restart for several hours.

All the tubes are connected, no obstruction in air flow.  After I adjusted the governor and the choke settings right before it shut down it almost kicks back in.  It doesn?t surge other than the attempt to kick back up.  This is an older unit so it does not have a way to get codes.  I?ve read many threads and tried all the suggestions to no avail.

Anyone out there ever had luck fixing this situation?

 

[DonTom]

I have a 1996 Onan 4000, model 4KYFA26100.  It?s mounted in a 1996 Fleetwood Tioga Montero Class C.  The generator  has 247 hours on it. When it runs, the choke opens as it should, power output no load is 120-125 volts. Tank is 3/4 full, fuel flow is present after the generator quits, tested spark, it only sparks when I release the start switch. Carburetor is clean, new magneto, new solenoid, new carburetor, oil switch disconnected, new fuel filter.  I have run through all the troubleshooting guides. I have the service manual. I have put a direct pick up tube in a gas can and run the generator, same thing happens.  Runs smooth for 10-15 minutes, cuts off, won?t restart for several hours.

All the tubes are connected, no obstruction in air flow.  After I adjusted the governor and the choke settings right before it shut down it almost kicks back in.  It doesn?t surge other than the attempt to kick back up.  This is an older unit so it does not have a way to get codes.  I?ve read many threads and tried all the suggestions to no avail.

Anyone out there ever had luck fixing this situation?

Is there an oil pressure sensor in there? If so, it could be intermittent (if your oil level is okay).

-Don- Auburn, CA

 

[Mtutton]

I have disconnected the oil sensor.

 

[jubileee]

? it only sparks when I release the start switch? You mean there is no spark when you?re cranking the engine? And this is after it?s started and ran?

 

[Old_Crow]

I'm led to believe that there are normally open oil level switches as well as normally closed ones.  The operation of the switch determines what you do with the disconnected harness. 
Did you short the wires together, or just leave the connector dangle?  Did you try it the other way?

 

[wackymac]

It sure sounds like a bad fuel pump.

 

[Isaac-1]

I agree bad electric fuel pump, classic symptom on these generators.

 

[Mtutton]

Fuel pump sounds like where I?m headed with it.  But something is interupting the spark when it shuts down. Not sure a bad pump would do this.  It runs great for 10-15 minutes, when it shuts down and I try to restart I can smell fuel.  I have pulled the fuel feed, cranked it over and fuel flows from feed.  Check the spark, there is no spark until I release the start button and it sparks once. 

 

[BruceR]

Check the spark, there is no spark until I release the start button and it sparks once.

It sure sounds like your points (or equivalent electronic device) aren't opening the circuit to allow the spark to be generated. When you are releasing the start button, YOU are acting as the points.

 

[stevensc]

Could the air vent on the fuel tank be closed or clogged.  I had this happen on a portable one.  Would do the same thing, crank, run for a few minutes, shut down, not crank until air slowly seeped back into the tank.

 

[skydivemark]

If you're sure you're still getting positive fuel supply when it dies, it sounds like it could be the ignition coil going failing when it gets warm/hot.

 

[Mtutton]

Already put a new ignition coil in it.  Still the same.  I still wouldn?t think a failing fuel pump would cause the spark to be interrupted.  I?m afraid it may be in the control board.