6 or 12
 

I bought a 1951, 239 and am wondering if it is a 6 or 12-volt system? I took the starter off because it wouldn't turn with 6 volts and turns with 12 volts. I thought since it is 1951 era it has to be 6 volts, am I wrong? May seem like a stupid question but you don,t learn if you don't ask. Thank in advance for any assistance I might receive.

Welcome!

If it is still original wiring, it would be 6 volt. If it came with a 6 volt battery, and it won't crank with 6, and battery is good and charged, the battery cables and their connectors are probably bad as it takes much more current to turn the starter at 6 volts than it does at 12. Here it might be a good idea to clean up all the battery cable and starter motor connections and re-try. If you see any corrosive crud build up around any of the battery cable connectors, the cables are probably toast in my opinion. You may also want to test and maybe replace the starter solenoid relay as it could also be bad introducing much voltage drop. Hope these ideas help!

What battery was in it when you bought it? Is it possible it was converted to 12v? Look for clues like a ballast resistor in the ignition circuit, a voltage reducer for the instruments, and accessories that are clearly 12v (like a modern stereo).

The starters can be converted to 12v using field coils from the later 50's Ford starters, and the starter will still look the same externally, only testing their resistance can detect the difference. If you have the starter out, I would check the brushes for condition (just remove the brush cover band) and do some tests with an ohmmeter. The starter could just be bad, now's the time to find out. Take it to an auto electric shop if you have doubts.

There was no battery or wiring for that matter I have taken the starter to a repair shop and it shows good. I have replaced all wiring from the battery to solenoid and from the solenoid to the starter. I do not have a switch as of yet so I ran a hot wire from the battery to the positive side of the coil and held a jumper wire from the battery to the center pin on the solenoid in an attempt to hot wire it. I will try it again and go from there. Thanks for the info.

Take a look at the generator and voltage regulator, that's where your answer lies.

If you are currently using a 6 Volt battery the cables have to be thick, like 00 or at least 1 gauge
This means all the cables including the ground cable. BTW, these trucks were 6 Volt positive ground originally.

All FoMoCo vehicles:

1928/55 = 6V positive ground // 1956 thru today = 12V negative ground.

I thought they might be positive ground as the positive side of the coil was routed to the distributor instead of the battery, . Before I try and start it, being positive ground, I put the positive side to ground and the negative side to hot? Please excuse the stupid questions.

What voltage did they say the starter was set up for?

The starter will work correctly either way, positive or negative ground, Same with the starter relay, lights, and instruments (except the ammeter may read backwards). The coil will also work either way, just better if wired correctly. Only the generator cares. What does the nameplate on the generator and voltage regulator read, or are they missing? Pictures will help a lot. But to answer your question, yes.

Starter is 6 volt

Then you are positive that it hasn't been converted to 12 volts? Many people, including myself, run 6 volt starters on 12 volts.

The vehicle was pulled out of the field after X number of years sitting there so am sure that it is 6 volt system. The generator has not been hooked up as of yet. will get you the info off of it if possible. Thanks for the answers so far. Data Plate is gone so what different way to I wire it for positive ground? Currently, I am at the stage just to start the motor without connecting the generator, just to see if it will fire.

It is a 6 volt starter

I don't think there is any need for additional info at this point. It's pretty evident that the electrical system is bone stock, so just keep doing what you're doing. Be sure to have a fire extinguisher handy when you're ready to start it. The (+) battery post goes to ground, and the (-) battery post connects to the starter relay. Are the battery cables as thick or thicker than your thumb?