MTFCA Forum

As I said in other posts, I am new to the model T world. My 1925 T Sedan is my first. That being said, my car only starts on mag it runs rough once started I switch it to battery and it smooths out. Is that normal? If I try to start it on battery it won’t start, why is that? My coils only buzz on mag, they don’t buzz on battery. Is that normal? If not, what could be wrong? I would appreciate any help. I don’t have a club member near me, I wish I did.

Do your coils buzz on mag when the engine isn't running? If so, you're really on battery. As to your other question.... no, it's not normal. Usually a T will run well on either mag or battery. Typically the battery is used for starting because of it's constant voltage not related to how fast the engine is turning over. Once started, you switch to mag. The mag output voltage is significantly higher than the six bolts from the battery.

Have your coils been rebuilt lately? What shape is your timer in? Plugs? Everything in the ignition circuit can cause issues if not in good shape.

I suspect there are some other T folks in your area. Hopefully someone will step up that is close enough to give you a hand.

Sounds like the Batt and MAG inputs are switched at the back of the switch, or possibly at the terminal block on the firewall. That being the case, your observations are exactly normal - coils buzz when you crank slowly, and the engine starts when you spin it. Then when you switch to the other input, it runs better.

CAUTION: When fiddling with those connections, ALWAYS disconnect the battery. The reason is, if you should accidentally apply battery voltage to the magneto, even just for a moment, you will probably de-magnetize your magnets, rendering the magneto inoperative. They can be re-charged in the engine, but it's a complex and precise operation.

With the engine off, should the coils buzz if you turn the key to mag? Mine doesn’t. It won’t start on mag. Like there is no spark. Is that normal? If not, how do I fix it? I can start it on battery and switch to mag and it runs better.

Your coils won't buzz on mag until the engine turns over, either by cranking or when running. That's why many choose to start on battery because the available voltage does not depend upon how fast you're cranking. Switch to mag once it is running. The mag puts out AC with the voltage depending upon engine speed. In any case, the mag voltage will be greater than the battery once the engine is running.

If you try to start on mag you'll need to advance the spark a few notches....on battery you'll want it fully retarded.

If you turn the switch to BAT before starting, you should hear the coils because they're getting current from the battery. (If you turn the switch to MAG before starting, you shouldn't hear the coils because they're not getting any current until you send it to them by pulling the crank real fast. Once started, most will run better on MAG than on BAT because the running magneto supplies more current than the battery does. If your car is the opposite of this, I expect you have some wires crossed.

When the switch is turned to battery, you will only hear one coil sing if the rotor is in position to close the contact for that coil in the timer. Then as the crank is turned, you should hear each coil sing in the proper firing order, 1243.

I really appreciate all the feedback, thanks guys!