MTFCA Forum

I'm trying to help an elderly friend on his Model T (1927 Roadster). He has a 12 volt battery installed but he is still running the 6 volt wooden coils and generator. He's using a ballast resistor (white porcelain resistor) that reduces power from 12 volts to 6 volts. We're having trouble with the car running for only a few seconds then dying. I have used this same setup (12 volt with the resistor) on a old tractor but I've never seen it done with the wooden coil boxes on the Model T. Can anyone tell me if that could be our running/dying issue? He says he used this setup for years yet he's driven the car little to none in quite a few years. I realize the 6 volt generator will not charge the 12 volt battery. He's using a battery charger to keep the 12 volt battery charged.

A charged battery would not cause the systems expressed, running then dying. Likely a fuel issue. How old is the gas in the system?
Start checking fuel flow from the carburetor back to the sediment bulb. Shut off fuel at the sediment bulb and disconnect at the carb - have someone ope the valve - should have a descent flow. If not drain some gas out of the tank let it settle and take a look for any stratification - gas & water.

My '26 has an NH carb and it started very easily...until it didn't. I had the same problem where the car would start and run a few seconds. I cleaned the fuel passages in the carb and it is back to starting and running well. I found sediment in the carb bowl that was a tip on what to do.

Does opening the mixture adjustment help? If so, it could be running lean. It needs to be a bit richer when the engine is cold. What kind carburetor does it have? If a vaporizer, it is a bit harder to get started when cold.
Next would be fuel line stoppage and or carburetor jets clogged. The fuel should run freely at the carburetor when the petcock is opened. If not, try the petcock at the sediment bulb. It should run freely there. If it does you can run a wire through the fuel line to clean it out. If it doesn't run freely at the sediment bulb, the screen needs to be cleaned out. Sometimes the fuel drain from the tank into the sediment bulb is clogged and you need to remove the sediment bulb and clean out completely. Our modern fuel tends to become like epoxy if it sets a long time. If so, you might even need to boil out the tank.

A 6 volt generator will charge a 12 volt battery, however if the starter is not rewound for 12 volts, it will slam into the ring gear and eventually either damage the ring gear or the starter bendix.
Norm

There is no need to drop the voltage for the coils. In fact it shoots you in the foot. A T will run much better on 12v. Problem may be a sticky inlet needle/seat running out of fuel. Open the bowl drain into a glass jar checking flow & dirt in the system. Do the same @ the sediment bowl.

Sorry for the late response - too many irons in the fire right now!

I appreciate the suggestions here. The car does have a vaporizer carburetor which I have removed, cleaned and installed a new needle and seat. I couldn't locate information on how to set the float so I set it about 7/16 - not sure if this is correct. I'm beginning to suspect ignition switch because sometimes it won't crank and all and sometimes it cranks, runs briefly and dies.

Thanks again for the help - I appreciate it very much.

first, your float is too low and likely will not run beyond what it gets from the "shot" of fuel it sees from choke
set the float to be level with the casting when upside down and that will be close enough

as for the ignition switch, it has absolutely nothing to do with the car not cranking...the starter button is it's own circuit apart from anything else

Lyndel,
Engine cranking is the starter switch, not the ignition switch. Not cranking is the starter switch, starter, battery, battery cables, electrical connections, ground, one of, some of, or all of the above.