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  #1  
Old 05-17-2007
danimal danimal is offline
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Join Date: Apr 2007
Messages: 4
Default Onan runs for 10-20 minutes then stops

I have a 1987 34' Pace Arrow. The Onan generator will run perfectly for approximately 10-20 minutes then start cycling (increasing/decreasing rpm). It will do this cycling thing for a minute or less, then just stop. I'm running only the air conditioner which is a Coleman 6757 mach 1 rotary 11,000 btu.

It won't restart immediately after this happens but, if I turn off the air conditioner and wait for the generator to cool off (or so it seems anyway) it restarts and runs fine for the same duration of time (10-20 minutes) then cycles and shuts off again.

The puzzling thing is it runs smooth as silk until this happens.

After it shut off I checked and still have spark and fuel, yet it won't restart for the prescribed 20 minutes or so. I was thinking possibly the fuel pump, but I disconnected the fuel line at the carb and turned the generator over after it died. The fuel pump is still working as I have gas to the carb. Checked the spark by using the old screwdriver in the wire and getting it close to ground thing.

Temperature (Arizona in May) is approximately 100 degrees. Is it possible for these things to overheat? I see guys out here in the summer heat 115 degrees running them for hours at a time and they don't seem to have a problem.

Is there anything else I can check myself before taking it somewhere?

The oil is clean and up to level. Spark plug is new. Air cleaner although not new, is not blocked that I can see. Also tried it without the air cleaner just as a troubleshooting thing. The MH is sitting on level ground.

Thanks

Dan

Last edited by danimal : 05-17-2007 at 06:28 PM.
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  #2  
Old 05-17-2007
hunter03872 hunter03872 is offline
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Join Date: Feb 2007
Messages: 23
Default generator

not an expert but does your gen set have a sw for winter and summer mine is near the carb. don't know if that is the problem but worth looking into
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  #3  
Old 05-17-2007
danimal danimal is offline
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Join Date: Apr 2007
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Yes it does. It's set to summer. I went back out and cleaned the guck off the carb, then made a proper air cleaner bolt. The previous owner was real big on duct tape, Velcro strips with adhesive backs (what a mess), and bungee cords. The air cleaner cover was held on with a 3' bungee cord taking a series of wraps around different things including the air cleaner cover.

The previous owner seemed like a nice guy, but he was definitely no mechanic.
I've sorted out lots of things on this unit including wiring, Replacing the accelerator pump diaphragm for the carb (leaking fuel on the intake manifold every time you stepped on the gas), replaced hinges and lots of latches (his favorite use for the Velcro), light bulbs, and just a good general cleanup and mechanical going over. Also buffed out 34' of old paint and she actually shines again. That alone took me three weeks.

After cleaning the carb and air box then adjusting the altitude setting to 2500 feet (previously set to 5000 feet) and lubing the Governor linkage the generator ran with the AC on for an hour. I actually got the pleasure of shutting it off this time. I'm not sure if it's actually fixed, but it's working for now and I'll continue to test it between now and it's maiden voyage (Memorial Day).

Thanks for your reply.

Dan

Last edited by danimal : 05-17-2007 at 10:17 PM.
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  #4  
Old 05-18-2007
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whodo whodo is offline
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Join Date: Apr 2007
Messages: 1,100
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Dan
In case you haven't already done this. Go to the onan web site an download a complete service/tech manual. It will answer all the questions you have, including part #'s.
Go to: http://www.cumminsonan.com/rv/ then click on Maintance Parts then click on Tech Documents then scroll through and find your particular generator.
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  #5  
Old 05-18-2007
danimal danimal is offline
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Join Date: Apr 2007
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Outstanding! Thanks for the link. I'm downloading the manual now. That's gonna come in handy for sure.

It might be in need of new points and condensor. Who knows when it had it's last tuneup.

Other than that, the manual says.............

Problem: Unit runs then stops.

1. Out of fuel

2. Low oil

3. Excess oil

That bit's been covered unless it's an intermittent fuel pump problem that I didn't happen to catch.

Like I said..........it seems to be working fine for now but this little problem might rear it's ugly head again.

Last edited by danimal : 05-18-2007 at 05:47 PM.
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  #6  
Old 05-19-2007
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bukhrn bukhrn is offline
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Join Date: Apr 2007
Location: Lanexa,Va
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I had same problem I had the with a generator that I used at hunting camp, (not an Onan)it turned out to be a bad low oil switch, designed to shut the unit down if the oil got low.
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  #7  
Old 05-19-2007
danimal danimal is offline
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Join Date: Apr 2007
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That's interesting too. It makes sense that the switch/sensor itself could cause the problem and not necessarily the condition (low oil). I believe it cuts spark though. A buddy of mine had a similar problem with his Robin powered portable generator and I noticed that it had no spark at all when the low oil switch was activated. I always had spark with mine even right after it dies which further puzzled me.

I went out this morning and tried to start it, and it wouldn't kick. Turns over fine, but wouldn't actually start. I was looking around in the bay and noticed fuel dripping from the main feed line. Turns out all my fuel lines were hard as a rock, weather checked, cracked and leaking in at least one place. Ran all new fuel lines from the main and reserve tanks to their respective valves and finally the carb.

I noticed that when you shut the generator off it did a big wiggle/shake just before it died and it was tugging on the hoses. Whoever installed the hoses cut em to length and they would move all over the place when it did the dying wiggle (well as much as they could being as brittle as they were). Apparently it would allow it to leak sometimes and other times not, which could account for the intermittent deal. Really surprised that I didn't notice it sooner. I put a little spiral/pigs tail in the new fuel line, kinda like a coil spring shape to allow for some movement.

Also got an eye and mouthful of gas. Yum!

Hopefully I got it this time.

Really appreciate all the input. Love these message boards. Kinda restores one's faith in cool people helping others out when it's needed.

Last edited by danimal : 05-19-2007 at 02:50 PM.
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