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onan coil

4K views 11 replies 6 participants last post by  GT_80 
#1 ·
Got back to work on my sears gt18, and got it running. Today I was gonna put a generic vacuum fuel pump on it, but when I tried to crank it, it wouldnt fire. Got out my test light and checked the coil, no fire on the points side. It should light a test light on both the hot side and the points side shouldnt it, when you turn the key to start?

Anyone know where to get one for less than an arm and a leg? It is the BG/MS 2980A engine with 2 plug wires in the coil.
 
#2 ·
I've heard that you can use the coils off of certain Harley motorcycles, I have a butchered Onan B series engine that has a coil from a Harley Davidson. You might want to check auto wreckers or anywhere else that deals with used motorcycle parts, if your problem is the coil.
 
#4 ·
Yeah, a harley 45 coil would probably work, they both have the wasted fire sysytem where both plugs fire everytime but, wouldnt that most likely cost more than a new onan?

I thought about two 12 volt coils off junkers, wired together might work.OR, wonder how hard it would be to take one regular coil and make a wire with one end at the coil, and two ends to go to the plugs?
 
#3 ·
I have never had a bad Onan coil yet- try filing and resetting the gap on the points, then check for spark. If that doesn't work, I think a Harley coil will work, or troll ebay for a used Onan coil
 
#7 ·
Got back to work on my sears gt18, and got it running. Today I was gonna put a generic vacuum fuel pump on it, but when I tried to crank it, it wouldnt fire. Got out my test light and checked the coil, no fire on the points side. It should light a test light on both the hot side and the points side shouldnt it, when you turn the key to start?

Anyone know where to get one for less than an arm and a leg? It is the BG/MS 2980A engine with 2 plug wires in the coil.
In answer to the part I italicized and underlined, With the key on, and the points open it should light. With the points closed it will not. When cranking with the starter it should blink.
 
#8 ·
the - side on the coil should flash when turning the motor over if your not turning the motor over while doing it the points could be open and no pwer will be going to the - side of the coil so turn the engine slowly by hand until the points close if it lights up then your coil isnt bad it probably the condenser that either has a bad ground or needs to be replaced its rare that a coil is bad unless its rotted
 
#10 ·
Thanks for the answers, I think now I have the answer. Going by what yall have told me, I think the points are bad. I have had to file them before, I just thought though that there should be power at the hot side and the points side of the coil when the switch is turned on.

Its amazing how simple the answer usually is.
 
#12 ·
I think between .019 and .021 but don't quote me- I usually just eyeball it to make sure they open a tiny bit, and I have had good luck with that. They rust up if they are open when the motor stops turning and it sits for an extended period of time. Thats why first thing I do if it doesn't have spark is check the points.
 
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