WG600 ignition problem

[JD8020]

I have a mower with a Kubota WG600 3 cylinder gas engine that just up and quit. It has no spark at the plugs. It has an electronic ignition. If I remove the coil wire from the center of the distributor cap and put a spark plug in the end of that wire, I have spark. Normally that would tell me either the rotor or the distributor cap is bad. I replace the rotor and distributor cap. I still have the same situation, spark at the distributor end of the coil wire, but no spark at the plugs. I have been working on engines for over 50 years and never had a situation like this. Does anyone have any ideas?
Thanks,
Roger

 

[peterwg600]

I have a mower with a Kubota WG600 3 cylinder gas engine that just up and quit. It has no spark at the plugs. It has an electronic ignition. If I remove the coil wire from the center of the distributor cap and put a spark plug in the end of that wire, I have spark. Normally that would tell me either the rotor or the distributor cap is bad. I replace the rotor and distributor cap. I still have the same situation, spark at the distributor end of the coil wire, but no spark at the plugs. I have been working on engines for over 50 years and never had a situation like this. Does anyone have any ideas?
Thanks,
Roger

I have a Cub Cadet 2182 with the same Kubota wg600 gas engine and after 18 years of faithful service, it has this exact same problem. I have replaced the distributor cap & rotor, tried Battery to coil plus connection and checked everything I can get to.
Only observation is that the problem seems to be somewhat intermittent.
After pulling everything apart and getting the cap & rotor installed, the engine started like new and ran on all cylinders but it died after about 5 minutes of run and won't fire again.

I would love to hear a solution!!

Peterwg600

 

[birddogger]

The one thing I can think of that may do that is slipped timing; leaving the rotor out of position for the spark to jump to the pole for the correct cylinder. Pull the spark plug(s) so it is easy to turn, bring the rotor to one or the other cylinder position and with a soft copper wire or coffee stirrer stick feel down into that cylinder to see if it is close to TDC.

That the problem would come and go is a little weird; that it might fall back into the correct timing to run is 1 in a million.
If these engines have an electronic TDC sensor maybe that is loose or dirty.

Unless they just have fakaka plug wires that are shorting out; I had an outboard motor that did that.

 

[JD8020]

I even replaced the electronic module. (very expensive) with no change. What I finally found -The wire from the coil to the distributor had a pin head sized dark spot on it. The dark spot was a result of the spark shorting to the frame. When I was checking the coil wire I moved the wire just far enough from the frame I would no longer short out. Roger

 

[peterwg600]

Thanks JD8020,
You just put your finger on the solution.
The high tension wires are covered by a metal weather cover that hides what is going on beneath it. I just removed the cover and rerouted the wire a little and presto! engine runs like new again.
I guess this tells me to watch for high voltage shorts on old wires.
Peterwg600

 

[peterwg600]

Premature conclusion. Engine did a repeat performance ...ran for a short time and died.
Coil has continuous power, no evidence of high voltage arcing and no firing whatever.
Very puzzling.
peterwg600

 

[Kytim]

The last 2 tractors I worked on that had this issue were also high hrs engines. Niether were a kubota, a early ford and a Massey Ferg to-30 (same engine basically) but the principles are the same. I went through all the normal stuff too, cap, rotor, plug, wires, points on early's and it would work then not. It became apparent it was a timing issue. there was enough wear in the dist bearings/bushings the timing would change as the drive gear would walk-up the teeth of the cam. when everything is reinstalled the gear falls back into proper alignment. time to look into your spark triggering mechanism for wear, it doesn't take much, a few thousandths, at each bushing because it is additive to the overall movement. Distributors are wear items too.

worth a shot to look into!

 

[birddogger]

The wires probably settled back to their old positions after some vibration from running.
What some more diagnostics? have someone try to start it while you watch the wires in the dark (night-time). The blue halos should point you to the trouble.

 

[sasquatchlink]

My WG600-B quit again. I am not getting spark out of the coil. Tried different coil wire even. I hooked a test light to the + side of coil and when I was turning over the motor it had no light , but when I released the ignition switch it lit up. until I shut the key off. This is a 1989 WG600-B gas .

 

[JD8020]

I finally got to the bottom of the problem with my WG600. It has been a long and frustrating battle. It would run fine for a while and then just die. The coil would fire a sparkplug laying against the block, but would not always fire under compression. I replaced the coil - problem solved. It runs better than it has for the past few years. I have never had a coil that would fire a plug consistently when not under compression, but when it was put under compression fire it only occasionally. Roger