I found a similar issue on another thread, but go accused of hijaking the thread, so I am starting my own.
Onan 4K (I will update with the Model #s tomorrow) on our 1993 Tioga Montara M was running fine, then, after I moved across the parking lot at a softball tournament, it would crank and run as long as I held the start button down, but as soon as I released it, it would die. I tried both buttons (inside and outside on the generator) and samething. I tried disconnecting the inside button thinking it was holding the stop position. Nothing!!
Generator had the proper oil level, checked the fuel, checked the air filter, said a few choice words and checked everything else that I could in the parking lot of a softball tournament!!
Did you have over a 1/4 tank of fuel most won't run once it it's a 1/4 or less this keeps you from running the engine low on fuel so coach can make it to gas station
If you had over a quarter of a tank of fuel, did you by chance have a load on the genset when you tried to start it? Most generators have to warm up a bit before they'll carry a load.
Magician
MCP, IEEE, CCP, BJCP
Traveling, Working, and Judging
There's likely to be a low oil sensor that is bypassed in Start but active in Run. Also, the genset probably runs on coach battery voltage in Start and 12VDC that it produces itself in Run. Some of these functions are handled by a relay or two, one of which might be bad. The ONAN service manual is about $20 and has excellent troubleshooting charts. This is ONAN's RV GenSet page. Has some discussion threads and you can order a manual: www.funroads.com
Expanding on j-d's post, the engine gets its ignition voltage from two sources. When it's cranking, the voltage comes from the start battery. When you release the start switch, the voltage comes from the generator itself. If you've had a failure of the voltage regulator, brushes or slip rings, or (much more pricey & what mine had) the rotor or stator, there's no voltage coming from the generator. But it may also just be a defective oil level sensor.
I agree with j-d; get the shop service manual for your specific model and go thru the troubleshooting procedures.
Jim, "Mo' coffee!"
'06 Tiger CX 'C Minus' on a Silverado 2500HD 4x4, 8.1 & Allison ('Loafer's Glory'); '07 Forester 2.5 ( the 'HANDBSKT'); '95 Toyota SR5 V-6 4x4 pickup, ARB locker, Bilsteins, Warn hubs & M8000, etc;
'94 968, M030 swaybars ('DOPPLER')
One item not mentioned yet is the "altitude adjustment", located about 5 inches above the oil dip stick. The dial is marked "0 -- 5,000 -- 10,000" feet. Make sure the altitude is set for the area you are in. The adjustment works similar to the old "rich - lean" knob on older outboard engines. Higher settings "lean out the engine" allowing a larger portion on air to gas. Lower adjustments give more gas, less air. On higher setting engine may run smooth and kill when a load is added. Too low may run rough or not start at all.
Mark
Mark & Jan "Old age & treachery win over youth & enthusiasm"
2003 Fleetwood Jamboree 29
I'm taking my RV to the Onan shop this morning for the same symptoms. We shut'er down before pulling into the gas pumps. Tried to fire up after filling, and had the same problem you are. I'll let you know what my diagnosis is.
Cris, Carol, Robbie, Cathy, and Reeses the Wonder Dog
2005 Four Winds Chateau Sport 28A
Thanks for all the responses. The gas tank was topped off the night before, so it was full. I checked the oil level and it was full. Don't think that I have an altitude gauge, but I was in east Texas, so altitude shouldn't be an issue. I have a service manual in PDF format. I checked a few things, yesterday, but did not have a star head socket to remove the control unit to check for codes. I am planning a trip to the automotive store today.
c&cschroed please let me know what they tell you. My nearest Onan certified repair shop is 75 miles away, plus I like to do everything that I can before I take it. I also like to sound like I know what I am talking about when I go into the shop, even if I don't have a clue. LOL
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