40 Ford electric problem

dewert

dewert

Member
My 40 will not fire unless I touch a wire to the battery (neg side) and then touch the coil when cranked. Do I have a short from ignition to coil? Not sure where to start.
 
Not enought info. What wire? Check your grounds, clean, remove rust and paint and reconnect. You may have a open connection. A short is when a positive wire touchs a negitive and you either have big spark or you blow a fuse or a wire will melt and theirs no connection.
 
Once you have it started with the ign on does it keep running?
If not you have and open.Key,broken wire,restister under dash.
If it does keep running,your coil could be on its way out and by jumping it, you by pass resister under dash and put more voltage to coil.
 
All you have in the ignition circuit is the wire from battery to the ignition switch, a wire from the switch to the resistor and another from the other side of the resistor to the coil. Check the 6 wire connections and if that's not the problem it's the switch or resistor. My choice would be a dirty arced switch. I found one that had the wire from the switch to the resistor with a poor splice with a sleeve over it and was intermittant. You can clean the switch. G.M.
 
G.M. said:
All you have in the ignition circuit is the wire from battery to the ignition switch, a wire from the switch to the resistor and another from the other side of the resistor to the coil. Check the 6 wire connections and if that's not the problem it's the switch or resistor. My choice would be a dirty arced switch. I found one that had the wire from the switch to the resistor with a poor splice with a sleeve over it and was intermittant. You can clean the switch. G.M.
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Thanks for the info. I will dig into the switch then the resistor. This has happened 3 times maybe 3 or 4 months apart so it is something right where your are telling me. I think the switch sounds like the culprit but it could just as easily be a poor splice. Thanks a lot. I had no idea where to start.
 
Here are a couple of wiring diagrams that might help.
 

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The resistance unit under the dash, gives full voltage when cool. And then lowers the voltage to around 3,5 volt.
If you crank th eengine a "long" time, it will get warm and lower the voltage to the coil.
And then you loose the spark.

1: check all ground connections
2: check the cable fom the negative side to the starter.
3: check the battery

And see to it that you have a well tuned carb and ignition system

There was a post here some weeks ago explaining how it worked, and if a remember right in the old days the shorterd the resistor with i coin, when it did not start.
 
Intermittin problem are the worst.Something to check.
The ends of wire with the connector,give them a good tug,They maybe held on by few wires,and the coating of the wire.You could try another newer type switch.
 
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