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Old 05-15-2011, 01:34 AM   #1
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Onan 6500 Propane Generator

Our Onan generator has suddenly decided it does not want to start. We've had zero issues in the past. It turns over like a champ but never "fires". It sounds and acts like no fuel is getting to it at all. Our propane tank indicates it is at 50% and the stove lights right up. Any one have an idea?

Thanks, Steve

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Old 05-15-2011, 03:42 AM   #2
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Be sure the vent tube off the generator pressure regulator is not clogged by mud dobber nest.

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Old 05-15-2011, 04:32 AM   #3
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How about the oil ? Dose it have a low oil cutoff? When was the last time th fuel filter was cleaned ?
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Old 05-15-2011, 06:38 AM   #4
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Don't think there is s fuel filter on a propane generator. I like the low/no oil pressure safety cutoff, That is worth checking. Take a spark plug boot off the plug and insert an old plug into the wire boot and lay the plug down on metal and spin have someone try starting the generator while you look for spark. If you have good spark then it is a propane problem. If no park then it is an ignition problem.

The other thing would be the propane shutoff solenoid on the fuel line coming into the generator. If that is not functioning then no propane and no start. Do you have an Onan manual on the generator? If so, there is probably a great trouble shooting section.
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Old 05-15-2011, 07:59 AM   #5
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As the other post said, the #1 problem is dirt dauber in the vent hose. I always installed a piece of screen wire over the end of the hose to keep them out. Also remember low oil will cause this, but too much oil will also. Lastly put your hand on the gas valve and see if you can feel it click open when you try to start it.
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Old 05-15-2011, 08:16 AM   #6
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A couple of years ago, I had the same experience. Suddenly the generator would not start. I did the spark plug check, and found there was no spark.

Eventually, I discovered that the problem was the main circuit board. One of the circuits had a break in it. With a new circuit board about $500.00, and a substantial wait for it, I had the circuit repaired for $20.00, and it's worked fine ever since.
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Old 05-15-2011, 09:53 PM   #7
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The 6500 LPG has both a fuel filter and a fuel shutoff valve. My Onan 6500 has the filter and shutoff valve just as the main supply line comes to the generator. The shutoff valve has a single wire attached. Mine was stuck closed. It should click when you apply 12 volts. I put 12 volts to the valve and tapped it and it freed up. (tap with the handle of a screwdriver not the big hammer)
If you do have to open the propane lines, to replace parts, the system has to be purged correctly or quite a lot of gas will escape even with the valve at the tank closed.......
Engine will start with low oil pressure but the engine will stop when the start button is released. With good pressure, that oil pressure switch completes the circuit for the "run relay' to keep the generator running.
There is a 5amp fuse on the control panel- F1 protects the control circuit board.
hope this helps.
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Old 05-16-2011, 12:37 AM   #8
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Few years ago my 6500 would start and run only as long as you held the start switch in. Problem was material build up around the brushs that was shorting out. Onan tech cleaned this residue off and has run fine since
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Old 05-16-2011, 10:31 AM   #9
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Hooligan, thanks for the detailed information. As soon as I can get out to the coach I'll do the things you suggested.

RvHauler and everyone else thanks also. I'll be on the lookout for mud daubers and such as that is as likely a problem as anything.

Thanks to everyone for the great advice.


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