Onan starts and dies

jjrbus wrote:
Fuel pump appears to be working well.

By "working well", do you mean that you have confirmed that it's still running when the engine dies?

I checked when pushing start button voltage goes to fuel pump. As generator dies voltage stops going to fuel pump.

It might be worthwhile to investigate WHICH happens first.

If the fuel pump voltage goes away while the engine is still running, then you have a reason why the engine quits a moment later.

Make sure the fuel cut off solenoid on the carb is working properly. It should allow fuel to flow when operating, and off when the engine is turned off.

Check that the fuel pump in the RV gasoline tank is pumping gas to the generator.

I had a 2002 Roadtrek 170 that the generator didn't run. Found a rat's nest in the engine cooling vanes, carburetor was all gummed up, and the fuel line was hard and brittle. Replaced the fuel line and carburetor and cleaned out the rat's nest. Fired it up and it ran beautiful. When I traded it in on a 2018 NeXus Phantom the generator started up and ran perfectly on the first crank.

I believe these are splash lube engines. Could be an oil level sensor?
It’s gas air or spark. And you’ve verified spark and verified it’s not getting fuel, but you haven’t verified fuel pump operating properly.

I have a clear fuel line to generator, there is no stoppage of fuel to the carb. The voltage to the fuel pump stops as the generator dies not before. Really wish I knew what I am doing.
Thanks for the responses.

jjrbus wrote:
I have a clear fuel line to generator, there is no stoppage of fuel to the carb. The voltage to the fuel pump stops as the generator dies not before. Really wish I knew what I am doing.
Thanks for the responses.

Clear fuel line only shows there is fuel in the line and nothing else. You can have fuel in the line and zero pressure or zero suction depending which side of the fuel pump you are looking at and still have fuel present in the line.

Fuel pump voltage stopping as the gen is dying is most likely the safety system turning off the fuel pump since engine is no longer up to speed.

Even IF the voltage to fuel pump was the culprit you should have a full fuel bowl in the carb which would be enough fuel to run the engine for several minutes or more.

You need to check to see if the fuel pump is indeed pumping fuel up to the carb at a sufficient rate.

Basically, disconnect the fuel line from the carb and extend that line to some fuel container and then try to start the engine (don't drop the height of the fuel line where you spliced any more than needed.

Should get a good flow of fuel into your container.

No or weak flow and the issue is the fuel lines, fuel pump and or fuel filter.

Good fuel flow then issue is not fuel line, pump or filter and then move on to the carb which is most likely where your issue is.

Some carbs have a fuel shutoff solenoid which gets stuck and often the carbs get plugged jet and emulsion tube from sitting unused for long periods of time..

Fair chance you may have carb issues and the carb needs taken off, torn down and well cleaned or replaced if a new one is available.

Thanks for the responses. Carb does not have fuel shut off solenoid. I pumped fuel into container by jumping power to fuel pump. There appears to be a sufficient amount of gas to carb, however I am not a mechanic so sufficient is my opinion. I have a fuel pressure gauge and am looking for the adapter to measure actual pressure.

I am under the impression that the start button overrides safety for starting. I do not know if this applies to my model? I did try holding the start button but gen died anyway.

Unless you have a very low pressure gauge, you most likely will not get a reading when dead heading.

Fuel pressure and carb engines is going to be 7 PSI or a bit lower.

Yes, starter button will typically over ride "safeties" like fuel pump and oil pressure cut out but that is temporary at best and some advanced safety systems may even limit the time they are over ridden..

Spraying starter fluid into carb and the engine continues for a few more seconds is a pretty big clue as to the problem..

Engine is starving for fuel, you have proved the fuel pump is pumping fuel, you sprayed starting fluid into carb and engine continues a bit longer..

Basically the troubleshooting done is pointing to the carb as the culprit.

Carbs get gummed up, floats get stuck, dirt clogs the jet and your carb needs serviced or replaced.

By the way, instead of starting fluid (Ether in a can), you can substitute spray carb cleaner like Gummout.. , Just spray in like starting fluid and will act as a burnable fuel for a few seconds. Much, much easier on engines that Ether based starting fluids..