MTFCA Forum

After my last few breakdowns on the road, I thought long and hard about what could be my repetitious problem. My Model T Ford would run happily for about a mile, and then it would surge and buck and the engine would quit. My previous problem with an very rough-running engine had been cured; and now, when the engine was idling, it purred like the proverbial kitten, and the car accelerated with satisfying authority. But then, after a little while, the Flivver would surge and buck, and the engine would stop running. Very perplexing.
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Then it hit me: Something might be blocking the vent in the gas-tank cap. Sure enough, the wooden board I had used to raise the seat-cushion up a half-inch had a gas-cap shaped indentation pressed into its surface. Oh, this stupid piece of wood was definitely blocking the gas-cap’s vent! This had to be the problem! So I cut the appropriate circular hole in the wooden board. I also dip-sticked the tank and it read only two gallons. Well, that didn’t help matters either. With a full tank of gas and an unobstructed gas-cap vent, I and my friend, George, struck out on the road, brimming with confidence as we headed for the Saturday afternoon cruise-in about eight miles away. The car ran smoothly at a steady 30 mph, slightly downhill for about ten or fifteen minutes and then began its familiar surging and bucking. I pulled into an upcoming parking lot to get out of traffic before the engine would quit completely. We let the car rest for about ten minutes, then fired it up again, made a U-turn and headed for home—now slightly uphill. And every mile or so, the engine would surge and buck like crazy, so we kept pulling into parking lots to let the car rest a bit, then restarted and continued our trip home.
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The car misbehaved like that until we turned off the two-lane boulevard and into a residential area where traffic was light enough that we could safely slow down to about 20-25 mph. At that speed, the engine performed normally. We got home, put the Flivver into the garage and started mulling over some possibilities. Surging and bucking are symptoms of fuel starvation, so I considered the carburetor. But that was an unlikely suspect as the carburetor had only recently been rebuilt because of the way the engine had been misbehaving. Another unlikely possibility was overheating, but I had not seen the slightest wisp of steam. No, that wasn’t it. What then? Vapor lock? Perhaps, but this problem also occurred back in January on a freezing-cold 20-degree day—and it’s pretty hard to get vapor lock in below-freezing weather.
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Guess I’ll disconnect the fuel-line from the carburetor and check the fuel-flow by running about a quart of gasoline into a bucket. I know that won’t be the answer, because I’ve checked the fuel-flow before, but I’ll check it again. I should also drain some fuel from the under-tank sediment bulb. Maybe some crud will fall out of it. I wish I could unscrew the darned thing from the tank, but it’s on too tight and I know better than to force it. Same deal with the strainer-cover. I suppose it wouldn’t hurt to insulate the fuel-line and the exhaust pipe as they are in fairly close proximity to each other. That’s about all I can think of.

The fuel strainer bulb may have corroded brass screens that obstruct fuel flow. Water trapped in the fuel line could cause the trouble.
If you have a distributor or master vibrator on your car, a bad condenser might cause your problem. If the gas tank has been coated inside, loose coating may be obstructing the fuel outlet, or some other bit of debris, like a dead insect or fragment of a gas cap gasket, etc, could cause the same issue. If you can get both ends of your fuel line loose, blowing it out with compressed air might get results. Blowing compressed air back into the tank through the fuel strainer might temporarily unclog it. If you try this, take the seat out, have the tank near-empty, and leave the gas cap off, and do it out doors. You might be able to use a mirror on a sunny day to look into the gas tank when it is nearly empty to see if there is any debris in it. /// If for any reason you cannot open up the fuel filter to clean it properly, that's probably where the problem is. Corroded screens, gummy deposits, and fine rust particles can plug it up. When the car is stopped, loose debris may settle from the screen, and once the car is running and vibrating and moving over the road, the debris gets agitated and the fuel flow causes it to plug the screen again.///

I used to have a 1952 V-8 Ford that ran like new.... until the gas tank was half full. At that point, it would "run out of gas" and quit. I finally got tired of it quitting on me, forcing me to get out and under and take the fuel line loose at the tank and blow back into the tank to get going again. Keeping the tank over half-full prevented the problem. The solution was to remove and clean the tank, which had deposits of varnish and crud in it. When the tank was full, or near it, the debris stayed on the bottom and caused no trouble. Once the tank was about half empty, the sloshing gasoline stirred up the crud and it plugged the fuel line inlet. After I removed and cleaned the tank, the problem disappeared.

[/image]It’s now time to remove the fuel tank, clean it out, clean or replace the fuel sediment bulb and that will probably solve your problem. When you found out you were blocking the vent hole that helped for a while which indicates there is a fuel flow problem.

So, you still have not pulled the sediment bowl & checked it & the screen?
Just draining the bowl into a glass jar can be an indication if there is anything but clean gas.
There can even be a small flake partially blocking the carb intake seat.
I have taken several sediment bowls apart to find completely clogged screens except for a hole in the center punched thru to solve a poor fuel flow problem. The quick farmer fix.

I once had modern (63 vintage) Ford that would crap out @ moderate to high demand. After a bunch of hair pulling I took the top off the carb.
There was a dead fly that would suck down in the vortex & plug a jett.

The very first thing you should do which does not require taking anything apart is to simply open the petcock on the bottom of the fuel shut-off bulb and stick coat hanger wire straight up through the bulb and into the gas tank to clear any obstruction from the fuel tank into the bulb. Evidence that it is clear should be a good flow of fuel coming from the drain petcock. Also, if there is any crud in the bulb, draining some fuel will flush it out.

(As it is, you should carry a straight length of coat hanger in your tool box for the above purpose, especially if your fuel tank isn't clean/has rust.)

Doing the above, in and of itself, may solve you problem. If it doesn't, the next step is to remove, inspect and clean the screen and blow out the fuel line.

Many years ago, one of our club members had the same problem.

Removing the gas tank as a last resort to see what would shake out, a small quarter sized brass top from some product came out.

How the part got off the container and still remain completely new and unbent to get in the gas tank was another mystery that was never solved, but it would float around in the tank until the gas flow was strong enough to hold it over the gas outlet.

I had that problem for a different reason.

Most engines will backfire with the mixture leaned too much.

It used to seem to be a bigger problem with radial aircraft engines.

My first Model T was missing the carburetor air intake funnel.

I did not think it was important while driving on clean black top roads and I did not replace it.

The problem was especially noticeable on a cold morning with fog.

Most of these tours were in Maine, an area often cold or damp in the morning.

Another thing I would notice was frost on the carburetor near the air inlet when the engine stopped.

Giving the T a rest would allow me to start and continue on the tour.

Later I learned the Venturi Effect was causing the cold and frost that was leaning out the mixture.

Replacing the air funnel solved the problem.

Later in the day when the temperature came up ten degrees or more, the problem was not as often!