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Old 05-06-2020, 03:21 AM   #1
Karl
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Default Help Me -before I go mad

Its not often I'm completely lost but this is it

I have been chasing an intermittent miss in the 34 which I can't find
Completely stock set up 6V Mike Driscoll Distributor Skip Haney Coil Uncle Max rebuilt Stromberg 48

Its a long story but I have completely hit a brick wall and I really need some help. I have had an intermittent miss for last 4 months intially was just a slight stumble at speed but has got progressively worse. A couple of months or so ago after 5 minutes driving the car began to buck and miss and even with full gas 30 mph was the most it would go As I slowed down to pull over died completely and would not start . My wife towed me home.

Found I had 4.3 Volts to the coil but absolutely no spark . Ok That's easy Coil or condenser. Since I have no way of testing the coil and on a 34 Taking the coil out is the easiest way to change the condensor I changed out both with a condenser that tested fine and a new Skip Haney Coil . Started right up but still continues to miss. Slightly lumpy at idle . but good spark to the plugs I have changed the condenser twice . I have changed the Distrib Caps , I've changed the plugs . I have checked and rechecked

Yesterday It did same thing (in the same place) after 5 minutes on load missing badly jerking and jumping and max 25mph at full throttle I pulled the choke didn't improve but back fired . After about 4 mins of this it came right . Tonight in the garage I have run it in the dark no shorts anywhere that I can see. I removed the plug leads and I have A nice juicy spark that jumps at least 1/4 inch to each plug. Suggesting to me that the ignition circuits are ok and the condenser/Coil is good

I did notice some garbage in the fuel pump bowl (Mike Driscoll rebuilt Fuel pump with a bowl) I have installed a fuel filter and Cleaned out the carb and all the carb lines even tried running my spare 97 and no improvement.

The only thing I can think of now is the plug leads or perhaps the surpressors on the leads for the radio -However I just can't see that multiple leads would all fail together -and then come right.

Have no idea what to do next

Help -Karl
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Old 05-06-2020, 03:38 AM   #2
fordscript
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Default Re: Help Me -before I go mad

Sounds like might be the rotor....old originals do go bad, new repros are suspect. 4.3 at the coil is low enough, what is the generator charging? I don't know, but are Skips coils built to be 4.3 volts or 6? Just a thought.
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Old 05-06-2020, 04:58 AM   #3
Mart
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Default Re: Help Me -before I go mad

I'd also be looking at the HT side of the ignition. The HT loads need to be low as the spark will try and find the path of least resistance. If you have resistor plug caps, ditch them. Make sure your plug gaps are at .025" no wider. On a helmet, the most likely culprit is the rotor. A new rotor, along with losing the resistor caps will probably fix it. You can put a couple of layers of shrink tube on the distributor shaft to help stop the rotor/shaft spark leak path.

My experience is mostly with the crab distributor but all the same things apply.

Mart.
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Old 05-06-2020, 05:27 AM   #4
50droptop
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Default Re: Help Me -before I go mad

Agree, it’s likely the rotor. There is one more thing you can check on the helmet; the screw that sets the advance on the breaker plate. I had a similar situation and found the screw was stripped, allowing the breaker plate to move slightly. Sometimes it was fine, other times it wasn’t. While checking the rotor, be sure to check that screw as well.
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Old 05-06-2020, 05:31 AM   #5
Terry,OH
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Default Re: Help Me -before I go mad

Remove the radio condenser at the ignition coil and check again.
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Old 05-06-2020, 05:59 AM   #6
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Default Re: Help Me -before I go mad

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If it's missing while idling, try pulling the wires off the plugs one at a time to find the cylinder that doesn't make it slow down.
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Old 05-06-2020, 06:35 AM   #7
Frank Miller
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Default Re: Help Me -before I go mad

Check your ignition switch and wiring to the coil. A loose or bad connection can cause what you describe. It might be getting worse as it heats up. Also if you have one of those resistors that varies with heat I'd look at that too.
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Old 05-06-2020, 06:48 AM   #8
David J
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Default Re: Help Me -before I go mad

I have used Champion UD16 plugs for testing spark .
They have hollow stems and you can see the spark when running .
Easy to see any weak-dead ones .
Also easy to see if any intermittent spark .

On a completely different note my 34 was cutting out and losing power .
Couldn't find any obvious issues until loosening the gas cap cured it .
Never had that issue before and it turned out to be a plugged vent on top of the tank .
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Old 05-06-2020, 06:58 AM   #9
Don
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Default Re: Help Me -before I go mad

Ever check for plugged exhaust!
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Old 05-06-2020, 07:53 AM   #10
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Default Re: Help Me -before I go mad

I'm sure you've checked it, but you mentioned you saw some trash in the fuel bowl. Are you sure you have good, strong fuel flow with no restrictions? I have a '31 Model A that was acting the same way as you describe; driving along smoothly then started bucking, backfiring, spitting, and finally dies. The trouble was trash, rust particles blocking good, strong fuel flow to the carb. I had to install a fuel sediment bowl to strain out the rusty stuff. Once I got the fuel to flow properly, it runs fine.
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Old 05-06-2020, 08:10 AM   #11
51 MERC-CT
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Default Re: Help Me -before I go mad

Have seen similar conditions that were due to a cracked cork sediment bowl gasket (was sucking air not fuel)
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Old 05-06-2020, 08:28 AM   #12
alanwoodieman
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Default Re: Help Me -before I go mad

remove/change the rotor, while you are at it insulate the shaft with shrink tubing or electrical tape
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Old 05-06-2020, 09:19 AM   #13
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Default Re: Help Me -before I go mad

One more thing to check would be swap out the resister. It could be broken but making a connection enough to run but when it heats up breaks the circuit to the coil. Get a jumper wire with alligator clips and hot wire the coil from the hot side of the starter switch at the bottom of your steering column and see if it runs fine. That would tell you if it was the switch or resistor assuming no shorts in any of the wires.
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Old 05-06-2020, 09:29 AM   #14
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Default Re: Help Me -before I go mad

I had a similar thing occur on a clients '40 a few years back. Pulled my hair out trying to find the culprit. Turned out to be one bad spark plug. Nothing visible amiss and ran perfectly when cold.
In all my years, that was a new one to me.
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Old 05-06-2020, 09:34 AM   #15
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Default Re: Help Me -before I go mad

Quote:
Originally Posted by alanwoodieman View Post
remove/change the rotor, while you are at it insulate the shaft with shrink tubing or electrical tape


Can somebody post a picture of what is being suggested here?
Thanks, just trying to visualize it
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Old 05-06-2020, 10:31 AM   #16
Hoop
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Default Re: Help Me -before I go mad

This is a worn shaft and that's masking tape ... all used to illustrate where the shrink tubing or elec tape would go.


distshaft.jpg
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Old 05-06-2020, 10:38 AM   #17
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Default Re: Help Me -before I go mad

The Coil Wire can drive you crazy. Do change it and test drive I seen that before. You want a solid wire not carbon wire.
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Old 05-06-2020, 11:00 AM   #18
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Default Re: Help Me -before I go mad

Definitely not carbon "resistor" ignition cables. The cheap ones are also affected by humidity so that the problem changes with the weather. If you are running the spark plug wires through tubes, you may not be able to see the shorts, even at night. You can use the coil wound wire center ignition cables to for radio suppression without causing spark problems. Be sure to get 7mm spark plug wires, not 9mm, or you will have problems getting them to fit.
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Old 05-06-2020, 11:58 AM   #19
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Default Re: Help Me -before I go mad

Quote:
Originally Posted by Old Redneck View Post
The Coil Wire can drive you crazy. Do change it and test drive I seen that before. You want a solid wire not carbon wire.
I had something like this happen as well. My very original '51 came with this black bakelite cylindrical doohickey in the coil wire. I think it was a suppressor of some kind. I started having intermittent problems, so I pulled the coil wire and replaced it with a chunk of Packard 440, which solved the problem. (The doohickey had a Ford part number on it.)

Not that this has any bearing n the O/P's problem, since the '34's had an integral coil, but I thought I'd mention it anyway, on the chance that he has installed an adapter and remote coil.
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Old 05-06-2020, 12:23 PM   #20
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Default Re: Help Me -before I go mad

All good suggestions, but you're chasing your tail by taking short cuts. Why not do a compression test and hook up a vacuum gauge and go from there.
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