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Author Topic: Onan generator will not start  (Read 24502 times)


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Onan generator will not start
« on: June 23, 2012, 03:58:07 PM »
Hi, I have an Onan Microlite 2800 generator in my RV that will not start. 

Before taking it in for servicing, I thought I'd inquire here to see if anyone has had this same issue. 

This generator used to run, however has had a couple of issues with it previously.  I could not get it to start without tapping the throttle lever.  It would just turn over when I pushed the start switch.  By moving the throttle arm a little the gen would then start. 

Once the gen started, it would surge for a couple of minutes, then kick it and run normally.  The gen ran fine after that, once it was started and warmed up. 

Yesterday, it would not start after several attempts of adjusting the throttle arm.  I did however, get the gen running while I kept the start switch pushed.  As soon as I take my finger off the switch, however, the gen would die.

Any thoughts on these issues?  I was thinking of replacing the spark plug, air filter, fuel filter, etc.   I did take out the air filter and it looks fine, though I did notice it smelled like gas. 

Water Dog

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Re: Onan generator will not start
« Reply #1 on: June 23, 2012, 04:58:59 PM »
There is an excellent Onan trouble shooting guide here. If the generator "runs" with the start button held down, but dies as soon as you let off, there are about 4 possibilities. Bad circuit board, bad voltage regulator, dirty slip rings, or low oil pressure/or bad oil pressure sending unit. The trouble shooting guide tells you about these things and how to check the individual items. You can print it out and go over each one step by step. It sounds to me like maybe the problem you had before and the problem you are experiencing now may be two separate issues. The first sounds more like a fuel or linkage problem.

"Heart is where the home is"
Dennis & Vici Bernhard
2000 Bounder
1999 Jeep Wrangler
Home: Sumner, TX


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Re: Onan generator will not start
« Reply #2 on: June 23, 2012, 09:23:49 PM »
Thanks Water Dog!  I'll print this out and give it a read. 

Gary RV_Wizard

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Re: Onan generator will not start
« Reply #3 on: June 24, 2012, 09:07:57 AM »
I would do all the routine maintenance before taking it to a shop, and make sure they know it was done. No sense paying high dollar tech rates for routine things you can do yourself.

While you hold down the start switch on an Onan, you override a couple automatic shutdown circuits. Just what those are can vary by model, but typically it is the low oil pressure and no 120vac output tests. If it shuts down as soon as you let go of the switch, those are two things to check. Of course, the start switch also powers the fuel pump and starter motor.

Probably the most common no-start problems are fuel supply, so change the inline fuel filter and make sure fuel flows freely. Cracked fuel lines are a common problem too, allowing the genny to suck air along with fuel.
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL