Rough Running - Sometimes

[Michael in Sedona]

I have a mystery with my '29 Roadster. It's stock 6V positive ground but with an alternator. The car runs great most of the time, but now and then it will suddenly run very rough, like it's only running on two cylinders. This almost always happens if I give it heavy throttle on an uphill or in second gear while accelerating away from a stop. It will run rough and I can smell gasoline, then after two or three minutes it will suddenly run fine again. It's just like I had flipped a switch and cut out two cylinders, then flipped the switch back on and it went back to running on all four. It has conventional points. I have no idea of what it may be, and would welcome any suggestions. Thanks!

[Corley]

Just taking a swag here, but when you run her hard, you generate more heat. A couple things that this change in heat could affect are the condenser and the coil. If in fact you are miss firing, the unburned fuel will leave the exhaust with a gassy smell. After verifying point adjustment, I start by swapping out the condenser first, then if no joy, swap out the coil.

If those don't provide you with a smile, you might look at the possibility of a vacuum leak after generating that heat. A warped and leaking intake could cause this. In fact, this is a case where a vacuum gauge may be of help in diagnosing the problem.

So, it's probably a carburetor issue, huh? Ha!

By the way, I have no sympathy for you since you live in such a beautiful place!!!

[vic]

Just been dealing with a similar problem in that the car loses power on a long climb.......tried everything but to no avail....finally checked fuel flow from the tank and discovered just a trickle coming out...am now in the process of draining the tank prior to removing the tap to investigate blockage.
Good luck and let us know what you find.
Vic

[Michael in Sedona]

Originally Posted by Corley

Just taking a swag here, but when you run her hard, you generate more heat. A couple things that this change in heat could affect are the condenser and the coil. If in fact you are miss firing, the unburned fuel will leave the exhaust with a gassy smell. After verifying point adjustment, I start by swapping out the condenser first, then if no joy, swap out the coil.

If those don't provide you with a smile, you might look at the possibility of a vacuum leak after generating that heat. A warped and leaking intake could cause this. In fact, this is a case where a vacuum gauge may be of help in diagnosing the problem.

So, it's probably a carburetor issue, huh? Ha!

By the way, I have no sympathy for you since you live in such a beautiful place!!!

Thanks Corley,

I'll try some of your suggestions. I had thought that it could be the coil or condenser. I don't know how to check either of those things except to swap them out and see what happens.

Yes, it's a tough assignment to live here, but somebody has to support our local merchants.

Michael

[Michael in Sedona]

Originally Posted by vic

Just been dealing with a similar problem in that the car loses power on a long climb.......tried everything but to no avail....finally checked fuel flow from the tank and discovered just a trickle coming out...am now in the process of draining the tank prior to removing the tap to investigate blockage.
Good luck and let us know what you find.
Vic

Thanks Vic,
Somebody else suggested that the fuel flow might cause the problem, so I'll check it out. Once I figure this out, I'll let everybody know what the fix was. Thanks.
Michael

[Jacksonlll]

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Next time it does it, jump out and pour some water on the carb. If it helps, you know where the problem is.

[Jacksonlll]

If you just put on a new fuel line, it could be it is too far into the carb and restricting flow. Let us know what you find.

[steve s]

This could be something simple.

When you step on the throttle, more fuel/air mix is let into the combustion chamber, which raises the pressure in there, which makes it harder for the spark to jump across the plug gap, which makes those electrons pursue other options that might be available for getting to ground, which (as others have noted) makes engine misfire, run rough, expell unburned fuel, and possibly backfire in the exhaust system. If the car has good highway speed, the problem is NOT fuel flow, and you are experiencing another case of the old maxim that "90% of carburetor problems are electrical in nature."

The first thing to check is what other options might those high-voltage electrons coming from the coil have for getting to ground. Is one of the spark plug wires real close to, or possibly brushing against, the distributor body? Are the spark plugs' white insulators and the coil wire nice and clean? Scrutinize the inner surfaces of the plastic distributor body and the cap for maybe-faintly visible cracks or carbon tracks.

Try looking under the hood with the motor running at night, while you race the engine and watch closely for sparking that shouldn't be there: Sometimes, the load from acceleration of the flywheel is sufficient to possibly momentarily bring on the problem sufficiently for diagnosis.

[DHZIEMAN]

Originally Posted by Michael in Sedona

I have a mystery with my '29 Roadster. It's stock 6V positive ground but with an alternator. The car runs great most of the time, but now and then it will suddenly run very rough, like it's only running on two cylinders. This almost always happens if I give it heavy throttle on an uphill or in second gear while accelerating away from a stop. It will run rough and I can smell gasoline, then after two or three minutes it will suddenly run fine again. It's just like I had flipped a switch and cut out two cylinders, then flipped the switch back on and it went back to running on all four. It has conventional points. I have no idea of what it may be, and would welcome any suggestions. Thanks!

A car this old, if the fuel tank has not been "Fixed" is a rust generator, that some fix with an in line fuel filter. Sadly on a gravity system, these type filters are not the best at fuel flow. So that is one issue to think about. Next, if the fuel tank has not been fixed and the debris in the tank or fuel line of the Ford fuel filter or the filter screen in the thank gets all sucked up with rust on a hard run demanding more fuel, it may just be the rust dirt in the fuel restricting getting enough fuel to the carb and engine. A way to know is pull the line off at the Ford fuel filter and with a proper sized rubber hose, blow back into the tank, (to temporarily blow rust away from the filter screen in the tank) and then see how the car does on heavy climb or acceleration loads. If it improves briefly, then start looking for a way to solve fuel flow from the tank. Hope something shows up you can fix!