Onan 4K Issues

[LSC9901]

I have an older (1984) RV that has sat for a few years. I am now trying to get everything in order so it can be used. Our current project is the Onan 4K GenSet. When I press the start button the engine appears to be running but as soon as I let go of it the engine stops. The engine does appear to be running but it will not stay running when I let go of the starter button. When I got the RV the control panel on the generator had a very nice mouse nest in it. I did clean it all out of there but the K2 & K3 relays looking as though they have seen better days. In the trouble shooting section of the book it says that you should have 12 volts across the relay. There are many wires going to the K3 relay which I believe is the one that should keep it running once it is started. I was able to measure 12 volts across a couple of contacts but again there are at least 7 wires going to the relay.

So my questions are: 1.) Does this relay sound like the problem ? 2.) If not what other suggestions or test can I perform? 3.) If this could be the problem is there any chance I can find this relay locally and if so .... where. I am also very willing to listen to any other theories.

Thanks

[mrblanche]

If the generator is not producing any voltage, it will not stay running. Generators sometimes develop problems with the actual generator that will cause it to not produce voltage. It also won't run if it's low on oil, or overfull with oil.

[LSC9901]

It is neither low or overfilled with oil and earlier when it would run for a minute or two it was producing electricity ?????

[mikelcan]

When my generator did the same thing I found the fuel lines had cracked and were allowing the fuel pump to suck in air. I had to replace the rubber lines where from the tank to the metal tubing and from the tubing to the fuel pump.

Mike

[Guy an a dog]

Quote:

Originally Posted by LSC9901 I have an older (1984) RV that has sat for a few years. I am now trying to get everything in order so it can be used. Our current project is the Onan 4K GenSet. When I press the start button the engine appears to be running but as soon as I let go of it the engine stops. The engine does appear to be running but it will not stay running when I let go of the starter button. When I got the RV the control panel on the generator had a very nice mouse nest in it. I did clean it all out of there but the K2 & K3 relays looking as though they have seen better days. In the trouble shooting section of the book it says that you should have 12 volts across the relay. There are many wires going to the K3 relay which I believe is the one that should keep it running once it is started. I was able to measure 12 volts across a couple of contacts but again there are at least 7 wires going to the relay. So my questions are: 1.) Does this relay sound like the problem ? 2.) If not what other suggestions or test can I perform? 3.) If this could be the problem is there any chance I can find this relay locally and if so .... where. I am also very willing to listen to any other theories. Thanks

What model gen set do you have? Take a look at my thread some nice folks posted some links to repair manuals.
Onan gen-set ran for a minute......I need a manual

[bigskymt]

I had the same situation on a friends coach same vintage gen. but 6.5K.
If you can locate S-3 (oil pressure switch) remove the wire and short it to ground. S-3 provides the ground (-) for K-3 coil (run relay/ignition relay).
If you can locate R-1 Resistor it provides the + voltage to K-3 Coil. If it opens K-3 will not operate.
Both K-2 and K-3 are identical relays. Since your system cranks K-2 is not the problem.
The relays will have number identification on either the relay or the socket if they are plug in. Contacts 87 and 87a are normally open and close to provide the 12vdc to the ignition coil.
You should measure 12vdc+ at the coil when starting and running.
I'd look at S-3 first.
Good Luck

[EXIT INN]

Mine was doing the same thing you are talking about . Run as long as the button was pushed in . A buddy checked it out and I needed a diode . This fixed it for me . Good Luck .