Onan P224 Coil ?

[ARKANSAWYER]

  VA-Sawyer   Drum switch is bad.

[VA-Sawyer]

Sorry, Arky...Not the Drum Switch, but at least you are thinking far enough outside the box to possibly get it.
The FWD/REV system works ok. There is no chain binding, no problem with the belts or pulleys, and it seems to be traveling at normal speed in full foward or reverse. The ampmeter shows normal draw.
The main symptom is the ignition seems to break down when the FWD/REV switch is in FWD and seems to get worse as the feed motor needs more power.
VA-Sawyer

[amberwood]

coming in at a late stage here but this sounds very much like the voltage is dropping too low for the coil as the extra load is applied. Battery conditon? Alternator output?

DTR

[VA-Sawyer]

DTR,

That was one of my first thoughts, but pulling the heavist electrical load I could, debarker, lights, up/down motor raising the head etc, did not cause a rough idle.  A voltmeter on the + terminal of the coil shows better than 12 volts DC even while the idle gets rough when putting it in FWD.

VA-Sawyer

[jpgreen]

Something is grounding out intermittently when you go in forward feed.

What is it?

[jpgreen]

Bad keyswitch.

[jpgreen]

Does the problem happen only when the debarker is on?, or when it's off as well?

[VA-Sawyer]

Debarker has no effect on the problem. 

I suspected the keyswitch at one point. As I noted in my previous post, 12V DC at the coil + terminal doesn't change with the problem.

[sparks]

If this mill was built between 1992 and 1995 and it has the original power feed circuit board you could be shuting down the ignition system. The old style board would have one of the caps go bad which caused the board to bleed off current effecting the coil. As you increase the potentiometer the engine would begin to missfire. You would not see it in reverse because it is not controlled by the board.   Thanks

[VA-Sawyer]

Sparks,
Excellent !  Actually the mill is an '88 and I don't know if the board is original. I reached a point in the troubleshooting where I was convinced the power feed circuit board was causing the problem. I put my voltmeter back on the + terminal of the coil only this time I had it set on AC volts. With the engine not running and the key switch in the on position, I would get almost 2 volts of AC feedback when I put the FWD/REV switch in FWD.  Opened the speed control and found a loose solder joint on a capacitor. Re soldered the joint and fixed the problem.


OK Folks, here is what was happening... Because of the loose solder joint the capacitor was unable to do its job of filtering the AC feedback. The electronic ignition system was seeing this AC voltage and was false triggering the coil. When the coil is firing sparks at random times, the engine doesn't run very well. Also, these improperly timed sparks would sometimes happen as the piston was going up on compression causing the detonation I could hear and see the results of on the plugs.
So, there you have it. A very sick running engine caused by a bad circuit board that isn't part of the engine and is in fact, located some 3 feet away from the engine.  Go Figure !
VA-Sawyer

[sawguy21]

I have been anxiously awaiting the punch line. All that over a poorly soldered connection. Sheesh. Electrical problems can drive a good man nuts.