Home » Public Forums » GMCnet » Another Onan story
| Another Onan story [message #187876] |
Sun, 21 October 2012 15:51  |
Jiffyjet2
Messages: 86
Registered: November 2008
Karma: 0
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A few months ago we were on a short run, Onan running with the A/C on. Pulled over to get an ice cream and left the Onan running. When we came out, it had stopped.
Finally got around to looking into it last week.
When cranking it, no start, but when I let off the start switch, there was a huge explosion out the exhaust pipe. I mean loud, like a shotgun blast. This happened every time I tried to start it.
So, started trouble shooting. Although with the loud bang, it would indicate at the least fuel and ignition. But followed the trouble shooting procedure anyway.
Fuel was confirmed with the pump running and squirting fuel.
Started looking at the ignition system. The plugs didn't appear excessively wet.
Tried the starting fluid in the inlet and got nothing.
We put a spark plug tester on one of the wires and it was very strange. No spark while cranking but when I stopped cranking got one spark. Hello explosion.
Checked the voltage and impedance in the coil which appeared to be low. So got a new one from the Cummins dealer and a new condenser too, they didn't have a set of points in stock.
Put in the new coil, which by the way is a new part number and doesn't fit very well where the old one came from, but is doable.
That didn't fix anything, although by this time the explosion at the end of crank had disappeared.
So, replaced the condenser (capacitor) On examination of the old condenser it appeared to have gotten quite hot with the stuff in the top looking sort of bubbled.
Well, that apparently was the issue. Onan fired right up and was running like old.
So we swapped out the new coil with the old one since it fits correctly and it apparently was fine. It's running like it's supposed to. (not returnable, $99 bucks, but now I have a spare.)
I don't think I've ever encountered a bad condenser. For years I've replaced points and condenser but it was just something you did when you replaced the points, don't recall it ever being the root cause of an issue.
Live and learn, eh?
Jess
'74 Canyonlands
"the Great Pumpkin"
Tacoma, Washington
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| Re: Another Onan story [message #187881 is a reply to message #187876] |
Sun, 21 October 2012 16:25  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Jiffyjet2 wrote on Sun, 21 October 2012 16:51 |
A few months ago we were on a short run, Onan running with the A/C on. Pulled over to get an ice cream and left the Onan running. When we came out, it had stopped.
Finally got around to looking into it last week.
When cranking it, no start, but when I let off the start switch, there was a huge explosion out the exhaust pipe. I mean loud, like a shotgun blast. This happened every time I tried to start it.
So, started trouble shooting. Although with the loud bang, it would indicate at the least fuel and ignition. But followed the trouble shooting procedure anyway.
Fuel was confirmed with the pump running and squirting fuel.
Started looking at the ignition system. The plugs didn't appear excessively wet.
Tried the starting fluid in the inlet and got nothing.
We put a spark plug tester on one of the wires and it was very strange. No spark while cranking but when I stopped cranking got one spark. Hello explosion.
Checked the voltage and impedance in the coil which appeared to be low. So got a new one from the Cummins dealer and a new condenser too, they didn't have a set of points in stock.
Put in the new coil, which by the way is a new part number and doesn't fit very well where the old one came from, but is doable.
That didn't fix anything, although by this time the explosion at the end of crank had disappeared.
So, replaced the condenser (capacitor) On examination of the old condenser it appeared to have gotten quite hot with the stuff in the top looking sort of bubbled.
Well, that apparently was the issue. Onan fired right up and was running like old.
So we swapped out the new coil with the old one since it fits correctly and it apparently was fine. It's running like it's supposed to. (not returnable, $99 bucks, but now I have a spare.)
I don't think I've ever encountered a bad condenser. For years I've replaced points and condenser but it was just something you did when you replaced the points, don't recall it ever being the root cause of an issue.
Live and learn, eh?
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Jess,
I'm guessing that you did grow up fighting with Kettering (coil & points) ignition as much as many of us. Failed condensers were not that rare in the day and most often they got changed along with the points - because you had the distributor open and the condenser is cheap.. You now know that the fact that you got one spark means that the coil was probably good. Those are a vary rare failure. This is why all of the things that I have with points get something else put on as soon as I can figure out how to do it.
If you had read back a ways, you would have found that an old Harley coil will work and is way cheaper. If you know a Harley afficionado, or a private shop works on them, you could probably have borrowed a coil to try out. (Nice time to tell you - Huh?)
Now, I suggest that you go and read all the back postings about refitting the Onan with flywheel triggered Pertronix.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Another Onan story [message #187889 is a reply to message #187881] |
Sun, 21 October 2012 17:47 |
Jiffyjet2
Messages: 86
Registered: November 2008
Karma: 0
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Member |
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I'm waiting for Jim K to put together a kit for the electronic system. Everything else I have with points is already converted. The only way to go.
Jess
'74 Canyonlands
"the Great Pumpkin"
Tacoma, Washington
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