Running issues

Discuss all things Model T related.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules

Topic author
Dennis Pings
Posts: 4
Joined: Mon Jul 29, 2024 5:58 pm
First Name: Dennis
Last Name: Pings
Location: 1922 model T

Running issues

Post by Dennis Pings » Mon Oct 07, 2024 2:40 pm

I have a 1922 touring and lately I have had an issue with it running on magneto. I start it and warm it up and switch to magneto. It runs well for about 20-30 minutes. Then it starts spitting, sputtering and backfiring and then it will shut down.

When it will run on magneto, I have checked the magneto with a lightbulb and increased the RPMS and it gets really bright. I know it's not a fuel issue because when it starts to act up, I can switch to battery and it runs just fine. I have pulled the magneto lead and there isn't lint on it from the bands. I would think if it was a coil, it would act up but would continue to run.

I'm hoping someone here has an answer of which direct to go.

User avatar

DanTreace
Posts: 3813
Joined: Sun Jan 06, 2019 10:56 am
First Name: Dan
Last Name: Treace
* REQUIRED* Type and Year of Model Ts owned: ‘12 open express,'23 cutoff, '27 touring
Location: North Central FL
Board Member Since: 2000
Contact:

Re: Running issues

Post by DanTreace » Mon Oct 07, 2024 3:12 pm

Could be switch related, if internal contacts wander off, that would simulate the issue. Keep heavy key chain items off, they sometimes can sway and wiggle switch key.
The best way is always the simplest. The attics of the world are cluttered up with complicated failures. Henry Ford
Don’t find fault, find a remedy; anybody can complain. Henry Ford


Norman Kling
Posts: 4634
Joined: Tue Jan 08, 2019 1:39 pm
First Name: Norman
Last Name: Kling
Location: Alpine California

Re: Running issues

Post by Norman Kling » Mon Oct 07, 2024 4:31 pm

Does it change with the speed of the engine or the position of the spark lever? There is a difference between the way the timer works on magneto than on battery. On battery the current begins to flow when the rotor first makes contact with the segments in the cap and remains the same until the rotor passes that segment. However on magneto, the AC voltatge starts low and peaks with a sine wave. If one or more of the coils is out of adjustment, that peak might be different with each coil and the spark will come at a different time. You will probably notice that on battery, the timing changes with the movement of the lever. However on magneto, your timing comes in what I call "nodes". It will stay about the same as you move the spark lever until suddenly it either advances or retards according to which way the lever is moved. If the coils are out of adjustment, the fine timing could vary from coil to coil with the lever in the same position. Another thing which could cause it to run rough would be needle valve adjustment in carburetor. but that shouldn't make much difference when on battery or magneto. And of course the condition of the electrical connection from the magneto plug through the wiring to the switch and finally to the coils. So check all these things out. Whatever you do, be SURE not to accidentally connect the battery to the magneto or you will ruin the magneto.
Norm

User avatar

TRDxB2
Posts: 6262
Joined: Tue Jan 08, 2019 4:56 pm
First Name: Frank
Last Name: Brandi
* REQUIRED* Type and Year of Model Ts owned: Speedsters (1919 w 1926 upgrades), 1926 (Ricardo Head)
Location: Moline IL
Board Member Since: 2018

Re: Running issues

Post by TRDxB2 » Mon Oct 07, 2024 5:03 pm

DanTreace wrote:
Mon Oct 07, 2024 3:12 pm
Could be switch related, if internal contacts wander off, that would simulate the issue. Keep heavy key chain items off, they sometimes can sway and wiggle switch key.
I lean towards this as well. When the key is turned to either MAG or BAT one should feel the contacts settling to the indents that are on the backing plate.
The past is a great place and I don't want to erase it or to regret it, but I don't want to be its prisoner either.
Mick Jagger

User avatar

TWrenn
Posts: 3743
Joined: Sun Jan 06, 2019 10:53 am
First Name: Tim
Last Name: Wrenn
* REQUIRED* Type and Year of Model Ts owned: '13 Touring, '26 "Overlap" Fordor
Location: Ohio
Board Member Since: 2019

Re: Running issues

Post by TWrenn » Mon Oct 07, 2024 5:04 pm

DanTreace wrote:
Mon Oct 07, 2024 3:12 pm
Could be switch related, if internal contacts wander off, that would simulate the issue. Keep heavy key chain items off, they sometimes can sway and wiggle switch key.
I vote for the switch also.
Try it on battery for a day and compare.
I have the exact same issue with my '26 Fordor. Winter project...work on switches. Yes plural...I also have a repro that is even worse! :lol: :evil:


speedytinc
Posts: 4726
Joined: Fri Feb 12, 2021 12:24 pm
First Name: john
Last Name: karvaly
* REQUIRED* Type and Year of Model Ts owned: 14/15 wide track roadster. 23 touring, 27 roadster pickup, 20ish rajo touring
Location: orange, ca
Board Member Since: 2020

Re: Running issues

Post by speedytinc » Mon Oct 07, 2024 6:40 pm

If its the internal switch contacts, jiggling the key would effect a change running when on mag.
Try that experiment.
Weak & dirty internal contacts can be cleaned & bent for more contact pressure.
This is a common issue.

Post Reply Previous topicNext topic