Farmall Super A - Ignition Switch

[Brian Luton]

Was hilling potatoes tractor running smoothly and then suddenly quit. No sputter, no misfiring. Straight quit.
Now won't start. Notice ammeter needle does not move when I open the ignition plunger. Aside from that being odd.(and new) Everything seems in order.
The starter is cranking, battery is strong. Distributor cleaned and serviced, coil, wires and plugs all new. Fuel filter is new.
Battery is in good condition. Grounds and all wires seem solid.
Tried ether. Tapped on the carb float, etc. I have juice to the coil.

Does this all point to the ignition switch? Never had a problem with one before. Is there a way to test or bypass it altogether. This is our primary cultivating tractor and working unit for the farm. I need to get it running ASAP.

Any thoughts much appreciated!! Thanks!

 

[Charlie M]

If you have a volt meter you can check connections and narrow down the issue. I've had the terminals rust off of switches before.

 

[antiqueIH]

Replace the condenser.

 

[old]

If you have power to the coil then the switch can not be bad. If you replaced the condenser put the old one back in and make sure the point gap is still at 0.020 like it should be. Then check that you have a good blue/white spark at all 4 plug wire that jumps a 1/4 inch gap or more. You say fuel filter so you saying you have an in line filter?? If yes get rid f it since most are made for fuel systems with a pump and a gravity flow system does not work well with many in line filters

 

[BarnyardEngineering]

Not so fast there. I have had "juice to the coil" and it turned out that the ignition switch was bad. The analog voltmeter read 12V at the + terminal of the coil, but there was no spark. Changed the points, condenser, coil, cap, rotor multiple times, and still no spark.

The problem was the connection in the switch had become a high-resistance connection. A new switch cured the problem.

What you can do to test for a bad ignition switch is bypass it with a wire straight from the starter terminal to the coil. If the starter turns the engine over you've got good power there.

Take the center wire off the distributor cap and hold it near the engine block while cranking the engine. If you've got spark it will jump a 1/8" to 1/4" gap and be nice and blue.

 

[K-Mo]

Assuming you have points and condenser and not electronic ignition.
I found the best tool for trouble shooting the ignition system is a common test light. Connect a test light between the distributor terminal and ground. When you crank the engine the light should flash.
1- Light stays ON, the points are not closing or are dirty.
2- Light does not come ON, points are not opening, no power to coil or open coil.
3- Either 1 or 2, distributor not turning. Remove distributor cap and check for rotation. Sheared gear pin is not uncommon. Also check rotor alignment. A sheared pin may allow it to rotate the shaft after the gear has slipped.