MTFCA Forum

Being far from a mechanical expert, I am unsure what to do so my car runs better on battery. I am running a 1927 tudor with a Holley carburetor and an Atlas exhaust manifold - the same manifold that I have been using since I bought the car in 2006. The car has never been a strong runner on battery but now it is backfiring and has difficulty keeping the car moving. It doesn't backfire on magneto and can get up to 40 mph on the flat and pulls up inclines just fine; but...it doesn't accelerate as fast as it did - I would say it is running at 90% of what it was this past summer. Any idea why it has no power and backfires on battery and not on magneto. Thanks.

Simple, start on magneto and run on magneto. The Model T was designed to run that way, in fact the Owners Manual even says to start on magneto. Could be a fuel/carburetor issues. Not opening the spray needle enough, not adjusting the spark lever to engine speed. The battery is there for the starter and lights and as a backup for the coils.

Check your voltage on the battery side of the key switch. Kinda sounds like you’re not getting decent voltage from the battery.
Do you see any green corrosion at your battery cable ends ?
Battery posts clean ?
Is the ground cable firmly attached to the frame with a clean connection?

Just clean the timer.

PDGx wrote: ↑

Mon Mar 04, 2019 7:05 pm

Check your voltage on the battery side of the key switch. Kinda sounds like you’re not getting decent voltage from the battery.
Do you see any green corrosion at your battery cable ends ?
Battery posts clean ?
Is the ground cable firmly attached to the frame with a clean connection?

I will check the battery. You may be onto something there. It has been a year since I serviced the timer, too, so I will clean that out. Thanks.

If you have a wore out brass timer shield in that may cause trouble.

Nothing wrong about cleaning out the timer, but the car as he says runs fine on magneto, not so good on battery. I would check the connections and condition of the battery. The back firing could also mean the switch might need attention, not a good connection inside when turned to battery. My experience running on battery is, while it will get up to speed, it's just not as fast and does not seem to have the same power. When were the coils last checked or serviced?

Check the above. I will add a couple thoughts. Depending on what kind timer you have. When you run on battery, the spark comes as the roller, brush or flapper, (depending on the type timer) makes first contact with the contacts on the cover. If the leading edge is burnt away from sparking at the timer, it could be making first contact in a different place for each cylinder. When you run on magneto, the spark comes when the current in the primary coil reaches 1.5 amps. This would be somewhere in the middle of the contact.
Another and more likely cause of the problem is the adjustment of the coils. Some might only fire on a higher voltage than the battery. Since the magneto puts out up to nearly 30 volts as compared with 6 volt battery, you can see how this would happen.
I recommend that you have your coils rebuilt and adjusted by someone who knows how to do it such a person as Ron Patterson.
And if you find the timer to be worn, replace it with a new one.
Norm

Has the coil box been gone through and rebuilt? If it’s still in it’s original shape it’s time to rebuild it. You can be really surprised how much better a T can run with all new wiring and new copper coated coil box bolts in it.
It’s the heart of a T’s electrical system.

John kuehn wrote: ↑

Tue Mar 05, 2019 1:48 pm

Has the coil box been gone through and rebuilt? If it’s still in it’s original shape it’s time to rebuild it. You can be really surprised how much better a T can run with all new wiring and new copper coated coil box bolts in it.
It’s the heart of a T’s electrical system.

Yes, I rebuilt the coil box with new wood and cleaned up all the terminals when the engine was rebuilt in 2010. I also put in a new Anderson timer at that time. Working full-time, I have not had a chance to try out any of the ideas suggested. I do have two rebuilt Ron Patterson coils in the coil box. I also have a friend who has an original coil tester that I could see if they're putting out enough amps. Again, it's just getting the time to do it. I appreciate all of you taking your time to give me some suggestions to try.

Keep us in the loop Jim. I'm interested to hear if you find the issue.
The 18 here likes to warm just a bit before he's a happy four cylinder. Bat or Mag. Then he's ready to go.

I think Norm is on the right track. Clean up that timer and inspect it well. It wouldn't surprise me if you find bad contacts near their leading edge.