I have had many, but the one today was special. And I knew about this one, but I forgot that it could happen.
I have been working on the Onan on the M F 1855. It has been hard to start and has low power. It doesn't smoke at all and has good compression on both sides. The po said that sometimes it only ran on one cylinder. I took time to work on it again today. I have good 12 volts to the coil, the spark plug wires look to be in good shape. The p o had the wrong plugs in it (too short), so I decided to change them, as it was only firing on one cylinder. I had to wire brush the sparkplug threads in the heads (a good round wire brush that is used for cleaning 1/2 inch copper water line fittings prior to sweating them works great for this) to get the right plugs to thread all the way in. All I had were used plugs, but they are good, or so I thought. Anyway, I got the new plugs in and still it would only fire on one cylinder. Changed the wires around, changed the one plug with another one I had, it still wasn't firing, etc. It was getting towards dark, but I was determined to fix this problem. Then came the AHA! moment. By this time it was almost dark outside, and I tried to start it one more time....then I saw it. One of the spark plug wires was grounding out on the intake manifold bolt! I couldn't see it in the daylight! I cut a slit in a two inch piece of fuel line and put it on the sparkplug wire where it was shorting out to insulate it from that bolt. she runs great now and fires up easily!
Edited by Delmar, August 01, 2016 - 10:06 AM.