MTFCA Forum

Hello Everyone,

Round two. Finally got the steering issue straightened out, was buttoning everything up today from the long firewall job to get ready for cranking her over. All of a sudden I've got no spark.

I took the coil box off the old firewall and put it on the new one, other than lightly cleaning the contacts on the points and cleaning the insulators I did nothing else to the box, didn't mess with the coils, didn't touch anything else.
It did sit around in the garage for while, shouldn't think that would matter.

I have power through the switch to the terminal on the coil box (6.5-6.65V), but nothing else, coils will not buzz. I read somewhere to try to ground them and they will buzz, they did not. That terminal does seem a little loose, odd thing is I can't get voltage on the terminal bolt itself, only on the wire eyelet and the nuts that hold it on, tried cleaning it as to make better contact but no avail.

Does that terminal unscrew or does the box have to come out and apart?
It worked/ran fine before i changed the firewall. As far as I know the coils have never been out other than me taking out the box.

I can't think of anything I may have forgotten. I'll list what I did maybe someone can spot something I missed?

Changed the firewall, wood to wood, took coil box off touched up points, cleaned insulators, put back on new firewall.
Changed all wiring harnesses. all wires are in the correct places.
Cleaned timer, roller.
Even changed steering bracket bushing, cleaned and re-greased steering gear + new pitman arm.

Please point me in the right direction, my diagnosing skills aren't what they used to be!
Thanks

If you changed wiring does that include on the timer? If it’s off a bit nothing will buzz.

Did you turn the key on and try grounding each of the terminals on the coil box that the timer wires connect to? * Is the engine grounded?

TRDxB2 wrote: ↑

Fri Jul 22, 2022 8:07 pm

If you changed wiring does that include on the timer? If it’s off a bit nothing will buzz.

Yes, the wires are in the correct places.

TXGOAT2 wrote: ↑

Fri Jul 22, 2022 8:56 pm

Did you turn the key on and try grounding each of the terminals on the coil box that the timer wires connect to? * Is the engine grounded?

Yes, I got nothing.

The problem seems to me to be in the coil box somewhere, I just don't know that much about that part of the car to know where to start.

"That (Batt) terminal does seem a little loose, odd thing is I can't get voltage on the terminal bolt itself, only on the wire eyelet and the nuts that hold it on ..."


That's very odd. From here, it looks like that's where your trouble lies. If you can't get power to the battery contacts on the coils, it ain't gonna run.

So, it looks like I'm taking the box back out.

I know of a case with a 1950 Ford 6 cylinder car where the car had been running well in daily service, and one morning refused to start. All the usual checks were tried, and the car still would not. It would crank, but make no attempt to fire. After much piddling with points, substitute coils, etc, it was discovered that the wire connecting the coil primary to the distributor, which appeared to be in good shape, was not conducting electricity. The original equipment wire was about 8" long, heavy gauge, fully exposed, and fitted with high grade brass terminals. Once the "good" wire was replaced, the car ran perfectly again.

There should be a strip along the bottom of the coil box with contacts to the bottom of each coil.The coils are held down by the lid which should cause them to make good contact with that strip. I suspect that the bolt is either not making good contact with the strip. What year is your car? As I think I remember, the box on a 20 has a wire soldered to the head of the bolt and to the copper strip. I could be wrong. Anyway, you are not getting battery from the bolt to the copper strip at the bottom of the coil box. If the car has the switch separate from the coil box, the wires would go from the battery and from the magneto to opposite sides of the switch and the wire from the center of the switch to the strip at the bottom of the coil box.
Let us know what year your car is and whether it has a starter or crank only. There are wiring diagrams for each kind.
Norm

Norman Kling wrote: ↑

Fri Jul 22, 2022 9:40 pm

There should be a strip along the bottom of the coil box with contacts to the bottom of each coil.The coils are held down by the lid which should cause them to make good contact with that strip. I suspect that the bolt is either not making good contact with the strip. What year is your car? As I think I remember, the box on a 20 has a wire soldered to the head of the bolt and to the copper strip. I could be wrong. Anyway, you are not getting battery from the bolt to the copper strip at the bottom of the coil box. If the car has the switch separate from the coil box, the wires would go from the battery and from the magneto to opposite sides of the switch and the wire from the center of the switch to the strip at the bottom of the coil box.
Let us know what year your car is and whether it has a starter or crank only. There are wiring diagrams for each kind.
Norm

'22 starter car

OK,
I get voltage right up to that terminal. I just never took the box apart before, not looking forward to it, that's why I didn't mess with it when I had it out.
Do the coils just slide out once you take the contacts/terminals off?
Can I test them individually once out? How do you test them? I don't know what to look for.
I guess it's time I learned how!

TXGOAT2 wrote: ↑

Fri Jul 22, 2022 9:15 pm

"That (Batt) terminal does seem a little loose, odd thing is I can't get voltage on the terminal bolt itself, only on the wire eyelet and the nuts that hold it on ..."
That's very odd. From here, it looks like that's where your trouble lies. If you can't get power to the battery contacts on the coils, it ain't gonna run.

Check continuity from the BAT terminal on the box to the long strip on the bottom of the box - if you don't get a reading the bolt is your problem. A loose bolt in itself should be the issue, since tightening the nut against the insulator should remedy that. But the bolt should have a wire soldered to it on the inside of the box

“ Changed all wiring harnesses”.
It was working before you changed the wiring and the firewall and removed the coil box.

Sounds to me the coil box isn’t grounded somewhere.
Go back over the wiring sequence and double check it’s wired correctly. Don’t completely depend on the color of the wire. Follow each wire to the correct terminal by hand. Some wiring harnesses have a different shade than what it’s suppose to be.


Good luck!

Remove the coils from the coil box by prying up on the wood case of the coil , this way you will not change the electrical value set . Wire brush the three contacts on each coil. Since you clean the contacts inside the box they should mate up with clean coil contacts. Had a case where I had a set of coils that I was given for testing, put in the tester and had absolutely no readings at all,... Due to what I would call dirt accumulation on the contacts prevented electrical connection.

Even with an automobile that has a microchip, including the etimer, if a problem is detected, one starts with the ground. On the Model T, the whole frame is used as a ground.

Attached are pictures worth 3000 words showing the wiring and where the ground (negative terminal is located).

The ground in the electrical system will be where the spark plug screws into the cylinder head. Power up to that point is just switched on and off by the commutator and a vibrating coil which eventually gives that power to ground creating a spark

Ben, when you state that you touched up the points, are you referring to taking the coils out and cleaning the contact points inside the coil box? If so, and forgive me for asking, but is it possible that you accidentally/absent mindedly put the coils back in the box backwards?

The Model T electrical system has a number of ground points, with several which specifically affect the ignition system.

BigBen wrote: ↑

Fri Jul 22, 2022 6:58 pm

Hello Everyone,
........
I have power through the switch to the terminal on the coil box (6.5-6.65V), but nothing else, coils will not buzz. I read somewhere to try to ground them and they will buzz, they did not. That terminal does seem a little loose, odd thing is I can't get voltage on the terminal bolt itself, only on the wire eyelet and the nuts that hold it on, tried cleaning it as to make better contact but no avail.
........

So unless that is resolved all other solutions are premature. As stated by others, remove the BAT wire, remove the coils and then test for continuity from the BAT post to the terminal strip on the bottom of the inside of the box. Based on your findings of not have a voltage the bolt reading on the bolt itself would indicate that the coils are not getting powered. There is wire that runs from the BAT post to the terminal strip. By the way do you have a MAG post too or just the one?

Just the one, no MAG post

I never took the coils out until today, as far as I know, they've never been out.

Another local Model T'er whom I've known for some time saw my posts and actually stopped by this morning, he is going to test the coils for me, Thank you Bob! BTW, I didn't see your posts until just now.

There is continuity between that bolt and the bottom strip. I will clean all contacts up nice and see what happens, keep you all posted.

Just to clarify what has already been stated, the metal strip on the bottom of the wooden coil box is an electrical buss. It is connected to the either the magneto or battery by a wire. The coils are grounded by the action of the timer to complete a circuit for the flow of electricity.. . See diagram "contact plate in base of coil box.

OK everyone,
Thank you all for your help!

With the great help of another forum member that lives in the same town(thank you so much Bob), we've got spark!
I suppose taking the coil box out and moving it around, and sitting was just enough for some things to lose contact and corrode a little.

She should be ready for her 100th Birthday next month We'll have a shakedown cruise probably sometime this week.

Thanks again everybody, happy T-ing!
Ben

Ben...... Looking forward to next month's 100th Birthday Anniversary Run. !!!! Your 1922 touring has a lot of documented local history. Enjoy. !!!!....