tractor ignition problem

D Sellers · Sep 20, 2014

I have a '61 ford 2000 4 cyl gas that I bushhog with, been using all summer with zero problems. Was using it recently and it stopped running, just like it had been turned off with the key. I suspected a loose or disconnected wire. All wiring was in place, so I pulled the coil secondary wire to the dist cap out of the coil appr 1/2 inch to see if I had spark. To my surprise the engine started and ran fine. I thought I had found the problem, dirty/bad connection. However, upon pushing the secondary wire back in the coil, the engine died. Will only run with coil wire out about 1/2 inch. Good blue spark is jumping from coil to end of wire, but will not run when inserted. This tractor has a 12v system, coil primary resistance appr 3-4 ohms, no ballast res. used. Dist.cap appr 1 yr old, new points. Is it time for some new wires?
Tried troubleshooting with known good coil and wire from 641 and engine would not fire. I thought I had a basic understanding of ignition systems on these old tractors (mostly learned from reading on this site) but I don't understand whats going on with this one. Thanks
D sellers

Phil9N3667 · Sep 20, 2014

Just a guess, but could your points not be gapped correctly and retarding the timing?

teddy52food · Sep 20, 2014

The plugs are fouled.

Geo-TH,In · Sep 20, 2014

Why not use an old spark plug? Connect it to a spark plug wire. Rest plug against engine and see if there is spark. Do the same with the wire coming out of the coil. See if coil is making spark and then see if spark is getting to plug. No brainer, simple test.

Steve@Advance · Sep 20, 2014

Try replacing the rotor. It may have burned through, shorting the spark to ground. Also check the cap and coil tower for carbon tracking.

will in texas · Sep 20, 2014

try the condensor under the distributor cap that will cause that also

merlynr · Sep 20, 2014

You are raising the secondary voltage to the plug by making it jump a larger gap.

sotxbill · Sep 20, 2014

when a charged up coil discharges.....when the resistance in increased, the voltage goes up dramatically on a coil. when you pulled the wire out, you increased the resistance and the voltage more than doubled.

SO... the plugs are fouled, plugs are bad, compression is very low/high, plug wires are breaking down, rotor worn out/not making contact, or coil is failing, or points are bad, dist cap has cracks, moisture or carbon trails.

that will about cover it. Find out why 12,000 volts is not enough and 24,000 volts works fine.

Start with the plugs and inspect the whole electrical portion of the ignition system. Are the wires solid copper or carbon..

old · Sep 20, 2014

Very good chance that you have bad fouled spark plugs. Bet if you did the same thing at the spark plugs and had the coil wire in correctly it would also run

John M · Sep 20, 2014

Never heard of 4 spark plugs going bad at one time, as has been suggested here, more than once. I would tend to think, since you pulled the coil wire, from the coil, or center of distributor cap? then that's telling me that either the coil is going bad, which I feel is most likely at this point, or something in the cap, or possibly condenser!

D Sellers · Sep 20, 2014

Gentlemen, new plugs made no difference. A known good coil and wire from an identical tractor made no difference. I put new points in and gapped to 0.020. Tractor would only run with coil wire pulled 1/2" out. I think dist cap or rotor has gone bad, but both were replace appr 1 yr ago. What should the resistance value be for the wire running from the coil to the dist cap??? It seems that I have minimum or no resistance some where in the system with the wire pushed in the coil.
New plug wires may also solve the problem.
d sellers
Thanks for the replies, this is a great forum that shares much knowledge.

todd hamilton · Sep 20, 2014

If pulling coil wire out helped it you have weak spark somewhere from a narrow gap. Consider in these old ignition systems the gap is an "air capacitor" actually the wider the gap more time for actual capacitor (the condensor) to charge thus a hotter spark. In the old days on trouble like this we would do points, plugs, condenser as all three items can break down and ground the spark. If that didn't fix it next step is cap and spark plug wires. If that didn't fix it we would start looking for bad mechanisms in the distributor. If the distributor shaft wobbles the points will not open and shut properly. If you are not field working this tractor (plowing) run the hottest rated plugs for the engine. It will start better and not foul the plugs as easily (burns the crud off). Hope some these tips may help. Learn to listen to the engine like a musical instrument, that will help a lot.

todd hamilton · Sep 20, 2014

Also start with gaps on the wide side. As points wear and plugs foul they generally narrow up. This will make the engine more cold natured but will run better when warm.

Janicholson · Sep 20, 2014

I will second the cap and rotor as the issue. By the way rotors pass near the cap terminals, they do not touch them. If they are modestly clean, they are fine. Jim

fixerupper · Sep 20, 2014

Look at the center point inside the dist cap, where the clip on top of the rotor gets it's juice from. Could be the carbon contact plug is worn out or gone. Weird stuff like that happens. Jim

buickanddeere · Sep 20, 2014

(reply to post at 09:50:36 09/20/14)

What brand and model of plugs? If they are not Autolite 216 or 437. The tractor won't run worth a darn.
Also use all new solid core plug wires.
Was a new condenser installed as Will suggested ?
What coil polarity is being used? What is the battery polarity?

D Sellers · Sep 20, 2014

B&D The plugs are autolite, don't remember the number. Will get solid core plug wires. Have not installed new condenser yet (tractor is 20 mi away) Coil polarity is same as battery, neg ground.

Geo-TH,In · Sep 20, 2014

No I'm not, have the metal of the plug in contact
with the engine, just that simple.

Janicholson · Sep 20, 2014

Solid core wires (and magnetic suppression wires) have basically no resistance. Carbon wires will have about 5000 ohms per foot of wire. Jim

John B. · Sep 20, 2014

Well it sounds like you have excellent spark if it's jumping a 1/2" an inch. Like Steve@advance mentioned. I think once you insert your coil wire into the coil it creates a path most likely from the coil tower to one of coil's small terminals. I've seen this many times. The boot on the coil wire is most likely the cause of this. Carbon arc on a coil tower or dist cap is hard to see but it looks like a pencil mark. (if you were to mark a cap inside with a pencil you'll most likely have to replace the cap) Carbon in pencil lead is very conductive.

showcrop · Sep 20, 2014

Look on the underside of the rotor for a tiny patch of ash indicating that the spark is jumping to ground on the shaft.

tractor ignition problem

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