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Topic: Generator will crank and start, but quit upon release of button (Read 201 times) previous topic - next topic
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Generator will crank and start, but quit upon release of button
The Onan 4000 Genset on our 2001 26.5 LD has performed wonderfully until recently.  A few months ago, when we pushed the rocker switch on the panel to start it, the generator sounded like it started properly, but when we released the switch, it would stop.  We were told that if the green light next to the rocker switch doesn't come on, the gen will not stay on.  We also had it explained by an Onan man that we can "reset" the gen by pushing the bottom part of the rocker switch 3 times, and then proceed to push on the top part, and the green light will come on and when we release the switch the gen will keep running. 
When we did that, it worked fine.  Happy campers!  But now, that 3x push is not resetting it - so we can't get the gen to stay running.  We tried starting it on the actual genset switch outside, and the same results.  It starts, but when we release the switch, it stops.  Any insight on what might be needing replaced/repaired would be GREATLY appreciated.
Re: Generator will crank and start, but quit upon release of button
Reply #1 –
I'll tell you what I think I remember. It's been some time since I had a similar problem, which turned out to be a very expensive repair. What I think is happening is that the field coils are not staying energized.  So... what happens is that when you press the start button, 12v from you battery is applied to the field coils to create a magnetic field. As the generator turns, and starts, the 12v from the battery is dropped out and replaced by 12 volts generated by the generator. It sounds like, possibly, the rectifier for the 12 volts is not working (burned out); there could be a problem with the (secondary) windings  that generate the 12 volts, or something entirely different.... my memory is getting worse with each passing year !  IF, and that's a big if, the rectifier could be located on the circuit board. Hmmm, I guess it's also possible a wire from the windings to the circuit board could have been damaged by mice/rats or the plug into the circuit board could be dirty and not making good contact. If you are handy with a volt meter, and after finding the troubleshooting guides available for you generator, you might be able to track this down yourself. Playing with the circuit board would be an easy place to start, but, as I recall, it's a real pain to take out. Good luck!
Ken
Former 2009 MB owner
Re: Generator will crank and start, but quit upon release of button
Reply #2 –
Start with the easy stuff - is there _at_least_ 1/4 tank of fuel in the vehicle?


Pushing the top of the rocker switch engages the starter motor.  At this point, the generator is cranking because of electricity from the battery.  When you release the switch, it _should_ continue running because of combustion (burning gas). It's not. 

Pushing the bottom part of the rocker button engages the fuel pump (the generator fuel pump, not the vehicle fuel pump).

You need someone with some skill troubleshooting small engines who can look at it in person.  It's not rocket science, but some experience helps.

I would suspect fuel, especially if you have never replaced the infamous small piece of fuel hose above the gas tank that is prone to slowly fail.  That's a wild guess though.  We don't have enough information to make an informed diagnosis.

Rich
'03 MB in NC

2003 MB
Re: Generator will crank and start, but quit upon release of button
Reply #3 –

The problem of starting, then stopping when the Start switch is released can be cause by dozen of things, more than what can be listed here.
The most common is the oil level,  a low oil level will prevent the oil pressure switch's contacts from closing when the engine comes up to speed.
The Start switch provides 12-volt power from the battery to the generator's starter, ignition, and fuel pump, it also bypasses the oil pressure sensor.
When the Start switch is released, the oil sensor bypass is eliminated, without adequate oil pressure to close the switch's contacts, the power to the ignition is cut, causing the engine to stop.
When the Start switch is released, battery power is cut to the ignition and fuel pump, depending on the generator to produce the needed 12-volt power to continue running. If 12-volt power is not being produced, the engine will stop.
The generator's control board needs to 'see' 120-volt power generated to confirm the generator is working. A lack of 120-volt power output can cause the control board to sometimes shut down.

If the engine starts and runs for a short time before dying, it may be from a low fuel tank, the fuel supply to the generator is cut off if the rig's fuel tank is at or below 1/4 full.

Do you have the Onan owner's manual that would have been provided to the original owner?  It will have the proper reset procedure and instructions on how to read any indicated trouble codes, plus it will have a troubleshooting section.
If you have the manual and determine the trouble code, providing it to us would be helpful.
With the model and serial number, stamped on the generator's specification plate, online manuals can usually be found.

Check the fuel level and the generator's oil level to make sure both are adequate.
Beyond that, it will require deeper troubleshooting. Bad voltage regulators, rotors, and the brushes and rings are common issues with older generators, especially ones that have not been run monthly during the years, usually requiring the attention of a Onan Service facility.

Larry

Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Generator will crank and start, but quit upon release of button
Reply #4 –
When I first bought my LD the generator was doing like in the OP and I just kept restarting it every day or so until it finally stayed running. Never had any problems after that. I think it just sat too long without being run by previous owner.
Discuss anything with anyone and disagree agreeably. Always be polite and respectful.
Re: Generator will crank and start, but quit upon release of button
Reply #5 –
Hi Wmanthey;   You should have a Onan Emerald Plus. A 2001, the same as my 1999. An external muffler, two spark plug, two cylinder engine.  After about 2002, Lazy Daze switched to the Onan MicroQuiet 4KW. It has a one cylinder engine, runs at 3600 rpm instead of 1800 rpm, and has an internal muffler. That one has a trouble shooting LED code, and a prime position on the start switch. My 1999 doesn't. I don't remember a green LED either, so to help us out, the model number of your genset would help clarify which you have.
         As Larry mentioned, many coaches have deterioration of a rubber fuel line just above the fuel tank. This lets the generator run out of fuel when it tries to suck a large volume through that hose. There is enough in the hose to get it started; not enough to run. The pickup hose in the tank doesn't go all the way to the bottom. That is so you can't run the tank dry.  You can then drive somewhere to get more gas. If you think that hose section could be the problem, a separate gas can and a fuel hose connected to the inlet side of the little fuel pump, will let the generator run normally.  Try the oil level first, and then see if the oil switch is working.   HTHelps.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
 
Re: Generator will crank and start, but quit upon release of button
Reply #6 –
To all who have replied - THANK YOU!  I am taking your valuable insight with me (hard copy) to the local service folks today and will use your trouble-shooting ideas to hopefully remedy it.  I'll update the post once I get things resolved.  Thank you again for your kind help.