Fighting a "missing then stall problem" when hot

[topchop]

Battling this for several weeks now with no resolution, only frustration.

Basically, I am seeking an answer to a question at the bottom on this post.

59AB motor rebuilt 1 year ago. Ran fine.
At time of rebuild: Bubba distributor, Charlie NY 94 carb, can style coil bypassing the resistor.
Using ethanol-free gas, from the same gas station.
Over the winter, I replaced wiring harness under dash.

About 100 miles into driving this season, began the vapor lock symptoms...at temperature (185 degrees, both head temps) usually driving for 15-20 minutes, begin to buck and eventually stop on the road, wherever I am. Panic at first, then, oh well. After 20 minutes, it starts up and runs fine for a while. Condition repeats.
When it quit yesterday, I put fuel in the carb and tried to start to see if it was fuel starvation, and no. So it seems to be electrical.
I know everyone has remedy's and suggestions, and I've done most of them to no avail.

(One at a time) Replaced coil (NAPA 904), phenolic spacer under carb, replaced condenser (IH 200), inspected distributor and rotor.

This brings me to the ignition switch (toggle switch on column). The back of the switch has 3 posts. One for hot 6v, the other 2 are switched, going to the circuit breaker and the gauge panel.

Following is with cold motor.
When ignition off, I have 6.24 volts on hot post in back of ign switch. Zero on the other 2.
Ignition switched on, I have 5.85v to the 2 switched posts, and at the coil I have 5.82 volts.

Here's the question:
When I start the motor, the voltage to the posts in the back of the ignition switch is 6.1 for a second, then the vm goes crazy. Voltage at the coil is totally OL. Shouldn't it be consistent battery voltage on both connections?

Thanks in advance.

Oh, btw, still looking for a resolution.

[G.M.]

The voltage at the switch with the switch on and the points open
should be within a couple 10ths of the battery voltage. The jumping
around indicates a bad connection or generator problem. I would take
the switch apart and with a small screw driver CAREFULLY bend the 3
little ball tabs out about .030 being careful not to lose the little springs.
Put 1000 sandpaper on a real flat surface and holding slight down
pressure sand the ball contacts so they have small flat spots on the
ends. Do the same with the other flat contact plate. This will be arced
and the plastic will have worn groves. Use 320 to get it down smooth
then 1000 to take the ruff sand marks out. The two smooth surfaces
when they come in contact will then have more contact area. It don't
seem like much but the sanding ridges reduce contact area. I would go
with an original coil rebuilt by Skip, keep the IH-200 and make sure the
original resistor is in the line from the ignition switch to the coil. This
isn't a sales pitch for Skip but he has rebuilt the 32 to 48 Ford coils for
well over 20 years, has done about 23,000 of them shipping all over the
world. He may have had a dozen that had problems and they came shortly
after delivery. When you have a stock setup it's easy to trouble shoot. When
the coil is changed it makes it harder to find problems. G.M.

[petehoovie]

Use an analog voltmeter for measurements you're taking....

[Mart]

I have had similar problems that turned out to be the rotor or the cap. Are you talking Crab style or Diver's Helmet? I've had HT problems with both.

The divers style rotors can short through to the shaft. the crab rotors likewise. The crab caps can fail between the clips and the adjacent posts.

The car drives for a while then deteriorates at wider pedals then gets worse until it will not move. Once cooled down it will go again for a while. Numerous times I have limped back home a few hundred yards at a time. (Until I worked out what the problem was).

Mart.

[topchop]

Mart, it is the "V" rabbit ear distrib. cap.

Update: After having replaced the condenser with another "new" IH 200, it appears fixed. I say this because I spent 1/2 hour driving around the block (my neighbors now know I was having problems). Previously, that was enough for the symptom to show up. Not totally confident yet. Will be testing tomorrow a little more. I still intend to pick up an analog meter and also address the ignition switch (thanks GM for the tip).
I have an old swap meet stock coil (condition unknown) and a new MAC's coil, both in the trunk. I will send the old one to skips.

[Mart]

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If you have the old solid core leads, that would possibly (probably, even) explain the erratic readings on the digital multimeter when running.

Mart.

[G.M.]

Originally Posted by topchop

Mart, it is the "V" rabbit ear distrib. cap.

Update: After having replaced the condenser with another "new" IH 200, it appears fixed. I say this because I spent 1/2 hour driving around the block (my neighbors now know I was having problems). Previously, that was enough for the symptom to show up. Not totally confident yet. Will be testing tomorrow a little more. I still intend to pick up an analog meter and also address the ignition switch (thanks GM for the tip).
I have an old swap meet stock coil (condition unknown) and a new MAC's coil, both in the trunk. I will send the old one to skips.

You want to check the coils you have and look for some etched numbers
or letters on the bottom. Skip rebuilt some for several parts dealers and
they would have his date code on the bottom. That's the first IH-200 I
have heard of failing. When you get your analog meter I will tell you how
to hot check the condensers. G.M.

[G.M.]

"Checking Condeners" You need an analog ohmmeter, the kind with
a swing needle. Set it to low ohms scale and touch either probe to
the body and the other probe to the lead. Every time you reverse
the positions of the probes the meter should jump up to at least a
third the way up on the scale and slowly drop back to zero. You can
adjust how far the needle moves by changing the ohm range. There
should be NO reading at all when both leads are connected, if you get
a reading there is an internal short even cold. If the needle jumps up and returns to zero the condenser will work when the engine and distributor
are cold, almost all will pass this test. Now you need to heat the case
of the condenser to close to 200 degrees. Use a heat gun or some heat
source to heat it up. 200 is where if you have tuff fingers you can pick
it up between two fingers for about a second. Office worker will just
about be able to touch it. When hot do the ohmmeter test again and
the needle will act the same as the cold test if it is good. G.M.

[supereal]

I have an inline electric fuel pump, mainly to fill the carb bowl after the car hasn't been used for a long time. For the rare times the car exhibits the sputter and stop in very hot weather, such as this year, I turn on the pump, and it straightens out the problem. It only takes one bubble in the line for the mechanical pump to lose prime.

[50fordcoupeman]

I have had this exact thing happen to me on two different engine set ups. Both times it turned out to be the coil.

[mike in tucson]

Different line of ideas here.... how old is the gas? Winter gas in Rochester is significantly more volatile than summer gas up there....affects vapor lock a tad.
Mike