1948 Ford 8n

Looking for a little help here.
Tractor was fine till a few days ago, now it will start, but not run
Dies as soon as it starts. Have changed all parts, have fire to
everything as far as I can tell, but it won't run. I have a negative
ground. The amp meter used to discharge when I first turned the
key on, but not now. It will discharge when its cranking.
any ideas would be welcome. thanks

If you hot wire it from the battery to the coil it will probably run (do not keep running it this way, it is a test of the resistor only). There is likely a resistor (either a ceramic block, or a resistor built into and of the
wire from the key to the coil. Either way this wire or resistor is likely broken/burnt. The tractor uses a bypass circuit to let the coil have full volts when
cranking, then reduced volts for running. If there has been some conversion on the tractor from 6 to 12v, we will need to kow a bit more. The location of the
distributor is also important. Jim

uh? you do realize yer center reading 30-amp gauge won't display the 150-amps that the starter motor draws, don't you? Yer 4-nipple front mount needs the mandatory infamous ballast resistor to keep the front mount coil from melting. O.K. heres the deal, when starting, yer starter mounted solenoid basically applies full battery volts to the coil but the minute you let up on the tranny mounted starter button, you connect to the ballast resistor and it continues to run. In yer case, the most likely suspect is a broken ballast resistor ...or... the wire leading to the tranny mounted thumb switch. Its amazing what #12 brogans kenn do to a wire. Surprizingly enuff, yer starter motor don't care, positive (+) or negative (-) ground, it still turns the correct way. 12-volts just make it turn faster. the amazed Dell

What tractor?

My screen post title says "1948 Ford 8N". I've never seen an N series Ford with a resistor starting bypass. What am I missing?

The 48 8N does have a resister because it is a front mount distributor but it is not a by pass set up.

Always trouble shoot then parts NEVER the other way around or you can cuase more problem then you fix.

#1 make sure you have a good blue/white spark that jumps a 1/4 inch gap or more at all 4 plug wires.

#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fill a pint jar in less then 3 minutes

#3 check your oil bath air cleaner and make sure it is not full of mud and water

Hi guys, thanks for the info, I had already changed the resistor, but I went and got another one and tried that. no change.
it has a resistor that looks like a flat piece with a triangle of
posts on it. Would it have an in wire one too? I have changed the condenser, resistor, coil, points,rotor,and starter solenoid.I have checked for fire in the plugs. I have a 6 volt with a 8volt battery.
Been like that the 34 years I have had it. Also checked all wires for continuity. Any ideas would be appreciated.

Also front mounted distributor.....sorry forgot to put that in
earlier.

That tractor is supposed to be a positive ground, not negetave. that would mess up the amp meter. And those resistors can be a problem. For years ran our 44 2N, same engine and wiring setup on ignation, on 8 volt because was hard starting to get the extra voltage to points. Never had points burning. The 8 volt with resistor will give about the same voltage as a 6 volt without. Mine got so it would die and not restart the same day, Several different switches, no change, don't think any were bad. I first wired a seperate switch in system and went thru the resistor, that way I could go from one switch to a different one to tell if it was a bad switch, no change in starting or running. I finlay added a third switch in wiring but bypassed the resistor, starts better that it ever did with the 8 volt battery (that I could not get again when I needed a battery), I still have those other switches in system and if I turn one of them on with tractor running good and turn the switch without resistor off the tractor will start to act up and die, if before it dies I turn the switch without resistor back on it takes off and runs fine. I have no problems with burnt points. And as for burning points without a resistor if that would be a problem how would a 6 volt either John Deere or Farmall with battery ignation and no resisters ever in system run for years without ever burning points and that was heavy all day after day work? And I know there were no resistors in those systems as we installed them converting from mags.

They DO NOT HAVE THAT BYPASS CIRCUIT, They were not made that way.

The tractor was born with positive ground system, but if properly configured will operate equally well on negative ground. Reversing connections on the ammeter is part of the positive to negative ground conversion.

"And as for burning points without a resistor if that would be a problem how would a 6 volt either John Deere or Farmall with battery ignition and no resisters ever in system run for years without ever burning points"

Because Ford front distributor coils were designed to operate with the resistor, A 1.5 ohm primary round can coil was designed to operate without a resistor on 6 volts or with a resistor approximately equal to the 1.5 ohms in a 12 volt system. A 3 ohm primary coil is designed to operate with no added resistor in a 12 volt system. It is all in the type of wire used to make the primary winding. Both 1.5 ohm and 3 ohm coils have one continuous wire as the primary winding, the 3 ohm coil does not have a separate resistor inside the can.