MTFCA Forum

I've been a prevalent question-asker recently and I'm back with another one.

I have been a new T owner for about 5 months now, while driving my 25' Coupe on magneto and at higher speeds of around 30MPH, it will begin chugging like it wants to quit. This happens only on rare occasion, and it may be due to improper spark adjustment on my part, but it has happened enough for me to reach out for help.

I started the car yesterday and once it had warmed up I set it to MAG at an idle and it developed a small miss, set it back to battery and it smoothed out. I climb steep hills in low gear with MAG at low RPM and it chugs right up no problem. I have crank started the car on MAG as well, no problem.
But the chugging at high speed and the misses I have noticed have me concerned.

Does it sound like I have a weak magneto? Is it just real sensitive to RPM?

First thing I would do is to check the magneto contact post. Remove it and see if the spring is making good and steady contact or if there is some debris under it. Check the simple things first. Also the ignition switch could be losing a good contact on the magneto side. It sounds like you have an intermittent issue. Or in other words a loose wire or contact.
Good luck and welcome to the Model T world!

Take a analog meter set to volts and see what the magneto is putting out at idle and at running speed. You can attach to the magneto wire on the firewall under the hood and to a ground.

Tad- you probably already know this- but in case you don't- Be Careful in your testing! Do not allow the DC current from a battery to enter the AC current of the magneto. The simple mistake will remove the magnetism that is in your magneto.
Test...but know which wires you are testing!

Thanks all! I will disconnect my battery and run some tests.

MichaelPawelek wrote: ↑

Wed Nov 17, 2021 7:58 am

Take a analog meter set to volts and see what the magneto is putting out at idle and at running speed. You can attach to the magneto wire on the firewall under the hood and to a ground.

Why an analog volt meter?

"I have crank started the car on MAG as well, no problem."////
///// Your magneto is probably in good shape. You could have a problem with the ignition switch or wiring, as pointed out. Another possibility is that your timer needs oiled, or cleaned and oiled, assuming it is a Ford-type roller timer. Cleaning the coil box contacts and carefully inspecting the wiring might be helpful. The coils themselves may need adjustment. I'd look first at the wiring and the timer. If you don't have access to experienced assistance, some published material will be extremely helpful.

Digital voltmeters don't work reliabley around Model Ts, probably due to strong radio frequency pulses generated and radiated by the Model T ignition system. Most analog voltmeters are not affected.

Just for kicks ... and I certainly do not know why....

Check your timer!

My Hack was a well fed hard runner and then one day while out, gasp, bubble, burp and I know to switch to batt immediately at that point and have half a chance it will get me home.

Mag post? NO. Wire loose? NO. Switch? NO-at least on ohm meter.

Open the timer? It was one of those repo with the "S" molded in the cover, early production and the inside was...interesting, the contact arcs were 'cupped' and one slightly crooked. Told myself can't be it...but also told myself need to change it...so did. Had an original new in box Tiger, so went with the Royce Peterson permanent lube trick, and mounted it.

Car started on batt...switched to mag...went for a really long ride...no problem....go figure!

Been that way for near 8 years now,,,will start on mag, run on mag, and I swear, all I did was change the timer. For some reason, enough DC went thru to ground...where the A/C apparently skipped for the same set-up? Makes absolutely no sense to me as to why that might have been...just sharing an experience

I have a New Day I purchased from Tip Top Timers of Spokane. I've put 5000 miles on it with only occasional cleaning. My car will start either on battery or magneto and runs well. A friend experienced symptoms similar to what you describe and eventually tracked it down to a Tip Top New Day that had been crudded up by oil and condensate sneaking by the cam seal. He cleaned it and the car ran well.

There are numerous things that can produce the symptoms you describe. A google search will lead you to posts on this forum and others.

It was one of those repo with the "S" molded in the cover

Those things are notorious. The originals are good, and I hear the new ones from Spokane are too, but beware of a leaking cam seal. Brush timers don't get along well with oil.

Thanks all! I removed the timer, it’s a New Day brush, full of gunk, oil and debry. Cleaned it all out and it’s doing much better on MAG now. I will put some miles on it and see.

Now I’ve got another question about an ammeter.
My old one worked good, but the glass was cloudy and the face in rough shape so I bought another that looked much better, it’s a Sterling brand. It reads well at discharge but never shows a charge.
Any ideas what could cause this?

Tadpole wrote: ↑

Sat Nov 20, 2021 10:43 am

Thanks all! I removed the timer, it’s a New Day brush, full of gunk, oil and debry. Cleaned it all out and it’s doing much better on MAG now. I will put some miles on it and see.

Now I’ve got another question about an ammeter.
My old one worked good, but the glass was cloudy and the face in rough shape so I bought another that looked much better, it’s a Sterling brand. It reads well at discharge but never shows a charge.
Any ideas what could cause this?

The obvious answer is your generator isnt. On the unlikely chance that the meter needle is hanging up internally. Reverse the leads & see if the thing shows a charge in discharge mode. Turn on lights to increase discharge rate. Check generator running out put.

If your ammeter only shows more or less discharge, either you have a defective ammeter or your generator is not charging. If the ammeter shows discharge when it should show charge, and vice versa, it is connected backwards.

TXGOAT2 wrote: ↑

Wed Nov 17, 2021 10:33 am

Digital voltmeters don't work reliabley around Model Ts, probably due to strong radio frequency pulses generated and radiated by the Model T ignition system. Most analog voltmeters are not affected.

Thanks for the response. It's been a long time since I have thought about RF around cars. I wouldn't know where to go to get an analog voltmeter. Do they still make them?

I use this multimeter. Cheap and so simple even I understand how to use it!
Does not come with a aaa battery.
https://www.amazon.com/gp/product/B0029 ... UTF8&psc=1

John C. If you still have your old ammeter and you trust the readings it provides, wire it in series with the new meter you are trying to sort out. Connected in series both meters will give identical current readings, tho the' Charge/Discharge' indication will be reversed if the polarity is incorrect. If you distrust both meters, proceed as suggested above. jb