Testing coils, per1938 Bendix Scintilla procedure

[Buccaneer]

I rigged up the Ford Model T buzz coil with a 6V game camera battery,
and did the open air spark test per the shop manual.
It fired the 3/16″ open air spark gap great before the video a few times.
It did “okay” during the video, but afterward, only fired intermittent,
or not at all, then NaDa.

When I pushed the test button and it didn’t fire, I would hear a faint
buzzing by the coils. Stupid me tried to see if I could feel which coil
was buzzing / vibrating…… must have got too close to the secondary……
Lit me up like a Christmas tree hooked up directly to the sub station
transformer!…. OUCH!

I turned the lights out in the garage, then pushed the test button again,
and besides the buzz, I could see a faint glow, when looking under the
rear coil.
I pulled the magneto off again, separated the coils, and tested with
the Stevens tester, using the “probe” function to look for leaks.
I found none, and each coil fired on the Stevens at around 2 amps.

Totally confounded now, but wondering if it’s a grounding issue between
the magneto and powerhead mount, but that doesn’t make sense, as
all the “grounding” was done atop the mag plate, not on the powerhead.

The shop manual said to ground the Ford (T’s buzz ?) coil’s secondary,
which I did to the mag plate along with the other grounds.
Could that be an issue?

The reason for the trouble shooting, when I originally finished
going thru the magneto, new plug wires, condensers, etc.,
One cylinder was sparking at the plugs better than the other,
and it was determined not to be the spark plug.
Also, I could not even get a “pop” out of the motor when using
fogging oil, or gasoline in the carb, or cylinder.
Compression is 65 psi on both cylinders, so I would think that’s
good enough for a little action?

https://youtu.be/Ofc3FbXO2bM

Prepare to be boarded!

[Tom]

Try grounding the T coil secondary to the bottom post on that coil.  I don’t think you want to be sending secondary voltage to the mag plate.

Tom

[Buccaneer]

Tom wrote:

Try grounding the T coil secondary to the bottom post on that coil.  I don’t think you want to be sending secondary voltage to the mag plate.

Tom

Tom, I may try going directly to the ground on the buzz coil tomorrow.
I had all my ground connections at the mag plate, but the ground lead from the
bottom of the coil was hooked up there as well.

Prepare to be boarded!

[The Boat House]

You have found a leak. I have found that using
the Merc O Tronic, to test the ignition this way
has been the biggest benefit of having the device.
Several times, after having a motor that wouldn’t
start, I found a leak testing the coil this way.
Tubs

[Buccaneer]

The Boat House wrote:

You have found a leak. I have found that using
the Merc O Tronic, to test the ignition this way
has been the biggest benefit of having the device.
Several times, after having a motor that wouldn’t
start, I found a leak testing the coil this way.
Tubs

Tubs, I expected I had a “leak”, so I separated the coils again,
and retested them on the Stevens, using the “Probe” to check
for leaks…… no leaks found though.

The “glow” and buzzing under the coils may have been from the
secondary from the buzz coil being directly grounded to the mag
plate, as Tom M. suggested. I haven’t had time to play today yet,
but heading to the garage soon.

Prepare to be boarded!

[Buccaneer]

I redid the “grounds” on the magneto buzz coil test, this time with
the magneto sitting on the bench. It jumped the 3/16″ gap with no
troubles.
I put it all back together and spun the motor over with a drill, and
it will only jump less than an 1/8″ open air gap, and with the cordless
drill on high speed.
The grounding post that the arc jumps to, was grounded to the back
side of the magneto, so it shouldn’t be a grounding issue from the magneto
to powerhead.
The magnets on the rotating magnet seem okay, but one half might
possibly be a little stronger than the other.

May re-check the point gap tomorrow, and maybe swap out the condenser,
for lack of other ideas. Also, maybe I’ll run a permanent ground wire
between the magneto to powerhead some how.

VIDEO……..
https://youtu.be/cnUkvjpXfBI

 

Prepare to be boarded!

[jeff-register]

Tom,

To replace the vibrater coil a guy can use a double pole double throw relay. It vibrates to the normally closed contacts till they are pulled down & become open & spring open closing the other contacts causing an open/close action. Only one problem the pulsing action is too fast, added a .20mfg capacitor to slow down the charge rate to a mechanical rate & worked well. Fixed many merctronic viberators that way. Tried  with 555 chips timer chips & no good, they ran into thermo runaway & cook ed. Never tried silicone switching chips , SCRs.Even sounded like the mechanical vibrator.

Buck,

When using a dual fire coil, the spark plug with the lesser amount of resistance will fire to ground & the second hi volt terminal has enough electrical energy to fire the second output. Happens  in a split second. Try less resistance on your test pins by making the gaps a little differances. then you are putting the test close to actual running app’s.

[Buccaneer]

jeff-register wrote:

Tom,

To replace the vibrater coil a guy can use a double pole double throw relay. It vibrates to the normally closed contacts till they are pulled down & become open & spring open closing the other contacts causing an open/close action. Only one problem the pulsing action is too fast, added a .20mfg capacitor to slow down the charge rate to a mechanical rate & worked well. Fixed many merctronic viberators that way. Tried  with 555 chips timer chips & no good, they ran into thermo runaway & cook ed. Never tried silicone switching chips , SCRs.Even sounded like the mechanical vibrator.

Buck,

When using a dual fire coil, the spark plug with the lesser amount of resistance will fire to ground & the second hi volt terminal has enough electrical energy to fire the second output. Happens  in a split second. Try less resistance on your test pins by making the gaps a little differances. then you are putting the test close to actual running app’s.

Jeff, what you mention sounds similar to some plans I found years ago to rig up
battery ignition for a antique marine engine, using a Ford relay of some kind.
I can’t remember much about it, but it did work.

Currently the Bendix will only produce a weak
“open air gap” spark of less than 1/8″ inch when
spinning the motor over with my cordless drill on
high speed. I can’t even get the motor to fire on
fogging oil, or in desperation, ether!

Prepare to be boarded!

[Author]

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