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WD 45 Ignition/wiring issue

K

KS 640

New User
Recently had to clean out the gas tank on a wd 45. When placing the tank back on, I moved some of the wires around
the solenoid. The tractor has been converted to 12 volts and has an alternator, and a keyed ignition switch.
Noticed one wire came out of a wire fitting attached to the back main post(the post being the main terminal to
the positive battery wire) of the solenoid (it is a four post solenoid, two main post, two smaller posts at the side) Placed it
back into the same round electric fitting. (This wire goes into the ammeter, then over to the ignition switch)
The back post of the solenoid had two wires attached to it, one from the positive side of battery, the smaller wire
went to the ammeter. Now the tractor starts but when the ignition switch goes back to on
position from start the tractor dies. I check fuel flow and carb, everything has good fuel flow, so it has to be
an electrical issue. I do not have a photo, but any suggestions as to why the tractor starts on start but dies
in the on position. And how do I correct it? Thanks for any response.
 
Where do the 2 small wires on the solenoid go.

Do you have a direct 12 volt coil, or a 6 volt coil with external resistor.

If you have coil with external resistor, the resistor is designed to drop 12 volt battery voltage to operate the 6 volt coil. One small terminal on the solenoid is to energize the starter and this is obviously working. The second small terminal likely sends 12 volts to coil when starter is energized to give hotter starting spark.

If this is the set up you have check for a broken wire from switch to resistor and resistor to coil, or for a bad resistor.

If resistor or wire to switch is open the solenoid supplies voltage to coil to start but when solenoid turns off there is no switch voltage to coil and tractor dies.
 
The solenoid has two smaller posts one is marked with an S this wire goes to the ignition switch, to
a post marked SOL. The other small post marked with an I has no wire on it. The coil is 12 volt and was
replaced about three years ago. The wire coming from the ignition switch marked IGN, goes along other
wires, then goes behind and along the side of engine block to a ballast resistor, then to the ignition
coil. Looked at this wire going to the coil and it might be wore or broke. Changed points and condenser
about a year ago. Have never done anything to the wiring since I had it. All wiring done by a
previous owner.
 
(quoted from post at 15:33:37 11/30/22) The solenoid has two smaller posts one is marked with an S this wire goes to the ignition switch, to
a post marked SOL. The other small post marked with an I has no wire on it. The coil is 12 volt and was
replaced about three years ago. The wire coming from the ignition switch marked IGN, goes along other
wires, then goes behind and along the side of engine block to a ballast resistor, then to the ignition
coil. Looked at this wire going to the coil and it might be wore or broke. Changed points and condenser
about a year ago. Have never done anything to the wiring since I had it. All wiring done by a
previous owner.
Click to expand...

You say the coil is 12 volts. Given you say it has a resistor, the coil must be marked something like "12 volt External Resistor Required". That is basically a 6 volt coil in disguise, sold to many during 12 volt conversions. If it is a true 12 volt coil it should be marked something like "12 volt No External Resistor Required" and the resistor needs to go away. Which do you have?

If you run a jumper wire from the battery positive to the resistor input side and it stays running after starting the problem is in the wire from the switch, or the switch. don't leave the wire on for long without the engine running or it will burn the points if they are closed. Not likely a problem with power to the switch if the switch provides power to the solenoid for cranking.
 
I believe it is possible that the previous owner used a lesser used method to work what I call the ..voltage step up.. for starting. Usually the power is pulled from the I terminal of the solenoid for this. Another way to do this is to use a diode, on the ballast resistor is there a second wire on either the terminal that the wire that goes to the coil is on or on the coil itself? If so this wire is bringing full voltage from the large terminal of the solenoid that energizes the starter. A diode is placed in it to not allow voltage to feed back from the ignition and try to run the starter. This may make no sense to you but it may help others understand your problem. The woefully odd part of your problem is that normally if an ignition switch has power to it to energize the solenoid when held to start it should also have power to energize the ignition coil circuit. I guess I am counting on the fact that the wire you say is broke or questionable is your problem.
 
Finally found the problem, it was a broken wire. Found it by testing the wires.
Tractor now starts and runs again. Thanks!
 
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