504 Farmall starting issues

[Lauriehannula]

We have a 504 that has started for 27 years, but now it won’t. It turns over but as soon as we let go of the red starter button it dies. Battery is good, spark plugs new, cleaned carburetor, cleaned fuel strainer and bought new screen and gasket, cleaned points, checked spark plug wires and replaced resistor. She sounds beautiful but will not stay running. Help!

 

[Janicholson]

The most likely issue is the ignition resistor. When it fails the tractor will start because the resistor is bypassed for starting. (gets 12v to the coil so starting is easier) then in the run position, the resistor is put back into the circuit. Jim

 

[Janicholson]

In this parts diagram the resistor can be seen on top of the coil bracket. A mid 1960s Chevrolet ballast resistor works. Jim

diagram

 

[Lauriehannula]

I will show this to the guy helping us, we bought a new resistor and put it in.

 

[Donald in MN]

We have a 504 that has started for 27 years, but now it won’t. It turns over but as soon as we let go of the red starter button it dies. Battery is good, spark plugs new, cleaned carburetor, cleaned fuel strainer and bought new screen and gasket, cleaned points, checked spark plug wires and replaced resistor. She sounds beautiful but will not stay running. Help!

the 504 has a wire from the starter that bypasses the resistor to give the ignition system a full `12 volts when cranking for a hotter spark. when the starter button is released the system goes back to 6 volts. for normal operation. while the resistor some times fails . it could be a wire from the key switch could be broken. you should get a tester and check to see if there is voltage from the switch to the resistor and distributor .

 

[Lauriehannula]

Thank you I will let him know!

 

[used red MN]

Hello Laurie welcome to YT! Here is another recent post on the same tractor model same problem. I believe he had continued trouble after replacing the resistor because he monkied with the carburetor.
YT post on similar problem

 

[BarnyardEngineering]

I will show this to the guy helping us, we bought a new resistor and put it in.

So you already put a new resistor in? Then there must be something wrong with the wiring or the key switch itself.