Oman generator help

[kendad]

My 1998 Oman 9 k generator Starts immediately when switched on but then stops when the switch is released. Any idea how to fix this?

 

[RT Firefly]

Greetings,
Welcome aboard, if I missed you. Fuel, air and properly operating safety shut-offs. From what very little I know of generators, there may be over temperature switch (s), low oil pressure switch(s) and over rev switch(s). Is your fuel pump electric? Is it working? Better minds than mine will surely comment. Is your fuel filter(s) clean?

 

[kendad]

Everything is clean and it’s confusing why it starts and runs while the switch is held on

 

[Giggitoni]

After checking on oil level, etc, has Mr. RT mentions above, zero in on the “stop solenoid”. It may need adjusting or replacing.

 

[kendad]

Why would an adjustment be necessary if nothing was touched or changed, can it un adjust itself

 

[RT Firefly]

Greetings,
Mr. G. Good point. I'd forgotten about the stop solenoid. Yes, they DO go bad as well. We have an Onan 15kw and there is a set of breaker points under a cover that need periodic adjustment so, yes, things go out of adjustment too. NOT saying you have the above mentioned points but several things to check to troubleshoot.

 

[kendad]

Thanks I’ll check these out

 

[Ryles]

Likely could be the voltage regulator. I had this issue with my Onan generator in my RV. The generator won't continue to run if it doesn't sense proper voltage output. The start switch bypasses this requirement so when you release the start switch the generator won't continue to run if the VR is bad.

Flightsystems.com were great in assisting me with troubleshooting. Here's their troubleshooting guide that got me close.

https://www.flightsystems.com/pdf/onan-rv-troubleshooting-guide.pdf

Ryles

 

[Ski in NC]

Some Onans of that era have a water pressure switch that senses sea water pressure from the pump. Switches can be problematic due to the typical corrosion issues. Try a jumper across the switch terminals. I think it is a NO switch.

 

[Giggitoni]

Why would an adjustment be necessary if nothing was touched or changed, can it un adjust itself

In my case a few years ago (Onan 8 kw), the linkage to the stop solenoid failed. I had to rebuild it. Also, the adjustment nut on the solenoid may have backed off, and out of proper adjustment. I recall it being very sensitive to adjustment.

 

[motion30]

This is a classic symptom of a safety sensor either being bad or actually sensing a problem.

 

[Drake]

I had exactly those symptoms and was stumped too. It turned out that the raw water intake valve was closed.

Just sayin’.

 

[Lepke]

When you're holding the start button down, the safeties are bypassed while the engine starts and oil pressure is coming up. When you let go, the safeties control the stop circuit. So it could be anything to do with oil pressure and coolant temperature. Usually the sender, but could be a relay or bad contact in the wiring in the safety circuit.

 

[Pcpete]

Check the exhaust temp sensor. I got one directly from the sensor manufacturer at a much friendlier price.

 

[BruceK]

My older Onan MDKD stop/start solenoid has 2 "holds". One pulls the plunger across to allow fuel to flow to start, and after it starts the other one holds the plunger across all the time, so fuel flows. Your second "hold" could have failed. Can you look at it to see what it is does during the start process. You might be able to hold it across manually and see if it still runs.If it has failed the only solution is a new one, and for that, esp if you have the part number, check ebay as well as your Cummins guy.
But of course it can be something else, as others suggest.