| Another Onan story [message #187876] |
Sun, 21 October 2012 15:51  |
Jiffyjet2
Messages: 86
Registered: November 2008
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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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