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Re: Who loves and understands their Original Onan ? [message #358771 is a reply to message #358752] Fri, 18 September 2020 12:34 Go to previous messageGo to previous message
rgogan is currently offline  rgogan   United States
Messages: 82
Registered: February 2004
Location: Milwaukee, WI
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At the last GMC international rally that I attended in Iowa, I polled the attendees at a generator lecture for the number of hours that they had on their Onan's. I hold the record for that poll at over 2000 hrs. However, those hours certainly did not come painlessly.
I have made just about every imaginable repair possible and here are some highlights that others may have not seen:

1) Some models of the facet electric fuel pump came without a grommet for the 12v wire power supply. When running the generator, I would have intermittent failures especially when the generator would run rough and vibrate. Eventually, the fuse would blow randomly for no diagnosable reason. One night I was looking at the fuel pump in the dark and noted arcing between the 12v supply and the case of the fuel pump. The wire's insulation has worn through and the wire was grounding to the case causing the intermittent engine failure and eventually the fuse blowing. Prior to this, it had actually burned out some printed circuit tracings on the control board when I tried to insert an oversized fuse. I replaced the pump with a properly grommeted one and also the circuit board was upgraded to a new design totally covered with some type of silicon insulation. More happy times.

2) More recently, I felt that irregular running and random stopping of the engine was related to the mechanical points. I fooled around with every conceivable gap and filing the points without help. Finally I bought the point set from Applied GMC that allows adjustment when the engine is running. Still, I could not get a smooth operation no matter the gap or timing. Finally found that the wire exiting the point box through a narrow slit in the box that was without a grommet, had its insulation worn through. Replaced that wire and had excellent results. I had ordered the electronic ignition upgrade but never bothered to install it after that problem was fixed. More happy times.

3) The most challenging problem was the Walbro LMB 185 carb. Experienced more problems with erratic operation that did not improve with a carb rebuild kit. Still suspecting it was a carb problem, I sprayed light oil on the carb and intake manifold gasket and had a sudden change in the RPMs. Checked the intake manifold gasket and found it was not leaking. Finally found that the shaft of the butterfly throttle had worn out the bushing in the housing. I was lucky enough on Ebay to find an unused carb that had been sitting on an inventory shelf for 40yrs. It was a LMB 181 and externally was identical to the original Onan carb. I purchased and installed it, and despite all my previous problems, I am in love with this generator again. The operation is unbelievable smooth and power has been restored. Hardly any RPM change when both roof A/Cs kick in. This is even with the electric water heater in operation. Does anyone rebuild or rebush the throttle shaft?

This outlines some of my more unusual problems that can be easily averted with inspection of the wiring and regular lubrication of the throttle shaft bushing. If you would like to hear about the other 10 more common problems, let me know.
Bob Gogan

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