Model A Engine Intermittent - help I need an adult

[82AModelA]

I am in desperate search of a Model A expert... I have a '29 Model A with an issue I can't seem to fix. I need someone more familiar with A's, as I am not - this is the only one I have ever worked with.

When the engine is running, it will periodically start running rough - the keyword here is "periodically". I have a clear cap on the distributor and can observe that, during this event of running rough, it is not firing consistently. Also, if it happens to die during this event, it is flooded.

However, it is not always running rough. It will usually alternate between running rough for about ten seconds and it will come back around and run perfectly normal. When it is running correctly, it will accelerate perfectly fine and idle fine. In the rough condition, it will struggle to accelerate, and I can make it backfire like a rifle if I get really aggressive with it.

The event seems random to me. I cannot cause the event and I cannot make it come out of it through GAV or timing adjustments, or even the air mixture screw on the carburetor.

To keep it short, after all of the testing and trial and error I have done, the only thing that I have concluded is that for whatever reason it loses spark when it begins to run rough. I've tested my wiring according to the Les Andrews book multiple times and it always checks out fine.

Any help is much appreciated. I'm hoping someone might can point out something I'm overlooking. Like I said, I'm not a Model A expert.

[Als48]

Sounds like a poor connection somewhere, possibly bad switch.

[nkaminar]

Check all wiring. All connections should be bright metallic and tight. Check the ignitions switch. Wiggle the key when running rough and check the contacts in back. Check the ammeter for loose connections. If all else fails bypass the ammeter by making both connections on one screw to see if it is the cause. Make sure the high tension wires are shoved all the way into the coil and distributor cap. Make sure the moving point in the distributor is not grounding out on the cam because of wear.

[J Franklin]

When this happens do you attempt to wiggle the key in the switch? Are all the wiring terminals tight on the wires? Are the terminals tight on the posts they go to? Is the distributor shaft loose in the bushings? Does the distributor cap/body have any cracks or carbon tracing between terminals or to ground? Does the cap carbon button touch the rotor? OOps I have run out of thoughts right now. Your turn!

I was a bit slow posting this but it is still your turn.

[1931 flamingo]

A location might help................
Paul in CT

[82AModelA]

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The key switch is a strange story itself. I took the old key switch out and tested for continuity with a multimeter; I could never make it have continuity in the "on" position, but somehow I was still able to start and run the engine - go figure. Got a new key switch and tested it to make sure, and it tested fine. I put it in and that didn't change anything.

I also put in a new ammeter - made no difference. I never tried bypassing it entirely however.

The wiring and all of the connections looks fine. I've cleaned them and tightened them up if needed; made no difference.

The distributor body and cap is new, and all of the terminals have continuity as they should from end to end. The carbon button is making solid contact to the rotor. The high tension wires are making good connection, and I checked to see if the lower plate was shorting out and I never could make the bracket with the pigtail short to the plate. The pigtail is also in good condition.

The points are new, and I have thus far alternated between three new condensors and two new sets of points. I'm running the V8 points and condensor. All of the points and condensors are identical and came from the same source. I know there was such a thing as bad new condensors, but its hard for me to believe I could get three bad ones in a row.

I have not checked the distributor for wear in the bushings although it has crossed my mind. The worn distributor idea bothers me because it would seem to me that the engine would always run rough in that situation, but again I'm not an expert.

[Gene F]

It's either the switch, the wire running out and into the distributor, or the wire going into the distributor is too far in. (when it heats up it expands and just barely touches the housing due to the pressure on it.) The clear cap looks cool, but they are known to draw dampness for some reason.

[Gene F]

You need an adult....so how old are you, and how did you come to buy your car? I was 34 when I got my A, and I was BY FAR the youngest owner in my local club.

[82AModelA]

So Im in my twenties...pretty young for this hobby I know. Dad and I have an A together that he found. It was just what we wanted. Id say it was restored probably 25-30 years ago-we have no idea who did it or any history of the vehicle. Whoever did it did a great job. Not Pebble Beach quality or anything, but good enough. We arent interested in shows or anything, just something for us to enjoy by ourselves.

Btw, the clear cap is just for testing purposes. I got it when this problem started. Dad is a good mechanic, and I know enough to be dangerous...but we're both stumped at this point so thats why I joined the forum.

[Big hammer]

One place that hasn’t been talked about is the ground path starting at the upper movable plate to distributor, distributor to engine head, possibly engine block to frame ground. With a length of wire and alligator clips it’s easy to check ground paths or lack of grounds

[TerryO]

Test the cable from switch to distributor. I had an intermittent issue like this and it was the small repro cable.


TOB

[nkaminar]

Check for a poltergeist living in the ignition system. Hire someone to do a incantation to drive it out.

[JOES31]

Search out the closest Model A club in your area. If you are close enough to one,
search them out & join. You can get help from them.

[gdmn852]

Hello, the pop out ignition switch , both original and repro have been known to short out . Mr. Crabtree does an excellent job of rebuilding the originals , have one in my 31 . Snyders sells a screw in to the distributor so you can eliminate the switch. Condenser are another known problem. Keep at it ,let us know what you find.

[82AModelA]

Originally Posted by nkaminar

Check for a poltergeist living in the ignition system. Hire someone to do a incantation to drive it out.

I'll do some research and I'll likely focus my incantations on the distributor bushings, as I believe that is where my poltergeist is living. I'll do another good once-over on the wiring one more time first, as I could easily have missed something, but I feel everything has pointed me to the distributor. If all else fails, I will search out a Model A club in my area.

Thanks for all of the responses. My intention was to pose my scenario and see if I get a general idea on where my problem is located and come up with a list of different things to try.

Unfortunately, I'm not able to dive into the project at the moment as life has gotten busy. So I probably wont respond with any results good or bad in a timely manner.

Thanks again

[J Franklin]

For others: I once used foreign parts in a distributor and found that the adjustable point couldn't be held and would move in and out at times. This was an evident problem after having to adjust the points almost immediately and tried to move the point with things supposedly locked tight, NOT! I think the OP said his were modern points though.

[1955cj5]

You mentioned that if it dies during it's rough running event, "it is flooded".

Have you checked the carburetor float level, and the float valve?

[Richard Knight]

Ok. There are plenty of A guy's out there, but where is there. Might be someone real close that would help. If not search for a club. Trouble shooting in the forums is hit and miss.

[J Franklin]

Originally Posted by 1955cj5

You mentioned that if it dies during it's rough running event, "it is flooded".

Have you checked the carburetor float level, and the float valve?

I doubt the carb float would have any effect on the ignition loosing spark. It might be worth checking after the first trouble is taken care of.

[Rob Doe]

If you have a safety fuse replace the fuse. One of the less durable safety fuse holders has tabs at each end that are riveted on. I've had the rivets get loose and kill the power intermittently. The clamps that hold the fuse can crack and break off.

Temporarily remove the safety fuse setup by returning the source connection back to the starter switch.