MTFCA Forum

My Model T’s engine has been giving me fits for about two years. Just for instance, this summer, on the way to a car-show, the Flivver started bucking and a minute or so later, stalled out completely. The engine would restart, run for five or ten seconds and stall—over and over. Hagerty sent a flatbed to get the Flivver home.
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This past January, some relatives visiting from Florida wanted a ride in the horseless carriage. So, in mustache-freezing, 20-degree weather, the car started up like it couldn’t wait to hit the road. Go figure. Well, I should have known better than to venture out into that screeching cold, windy weather, but we did. After a couple of miles, the car started bucking, and a minute later, stalled out completely. Like last time, the engine would restart, run for five or ten seconds and stall—over and over. And again, Hagerty sent a flatbed to get the Model T home.
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This kind of thing has been going on for quite a while. My Model T buddies and I have performed the usual diagnostics, replaced the commutator, checked for spark, adjusted the timing, etc. We rebuilt the coil-box and ignition switch, replaced the spark-plugs and cables—in fact, replaced the entire external ignition system. After the breakdown this past January, I decided to send the carburetor out for overhaul, there being not much else to do on the outside of the engine.
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With the new carb installed and today being a beautiful day, I topped off the radiator, did a startup and warmed the car up with the hood off. Oh, it was idling smooth as wet ice. I guessed the newly rebuilt carburetor had done the trick! Yaaayyyy!!! So, I put the hood on and hit the road—but decided that maybe it would be a good idea to keep to my immediate neighborhood. Then, about a mile later, the same old symptoms came back: The car started bucking and then stalled. I attempted a restart, but again, the engine would stall out after a few seconds. Over and over. Very frustrating. Well, something in my skull went “clank” and I got the idea that maybe it would be a good idea to let the engine cool down a few minutes before bothering Hagerty yet again. Five or ten minutes later, I was able to get a restart, and with the right side of the hood open, I crept at about 5 mph through the couple of blocks it took to get the car home.
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Those are the symptoms. What do you think?

Try opening the carb drain cock with a pan underneath and see if a half gallon of gas flows out evenly.

I think John is on the right track. Your symptoms are typical of fuel starvation. There is likely a restriction somewhere, not allowing the fuel to flow. John's check should con firm this. If you have a filter in the fuel line, remove it. You should see a better flow on John's check.You could blow out the fuel line. You could remove the fuel outlet from the tank and check the screen in the outlet is not blocked. Make sure the small vent hole in the fuel tank cap is clear.
Hope this helps.
Allan from down under.

Check your sediment bowl for cleanliness, including a partially clogged screen, water and mud.... May need to replace metal gas line from sediment bowl to the carburetor... Do you have a shut-off valve at the carburetor, and is it open all the way when you do open the valve?..... Hopefully you had more than 2 gallons of gas in the tank when you started out, and going up a incline with that low fuel in the tank has a greater chance of stopping the engine.

Vapor lock fuel line to close to exhaust ?

Check to make sure the vent in the gas cap did not get clogged.

If I understand the symptoms right it sure sounds like a fuel flow issue.
There is a slim possibility of a thermal issue but that does not feel right.
Did it go farther or shorter on the wicked cold trip vs warmer trips?

If you haven't checked the sediment bulb, its time to do it. I'd first drain the tank & take a peek inside to see if there is any residue in the bottom. Then check for any crud in the gas. Next the screen in the sediment bulb. It may have done its job & needs to be replaced. If you replace it don't bother to solder it back, just use some RTV around the edge. Makes it easier for the next time. Best to use an 8-point 11/26 socket so its flats match the covers

Suffered the same symptoms on my 1910 Buick Model 10. Finally turned out to be vapor lock. I run the fuel line under the exhaust on my Model T's, have never had a vapor lock those cars.

I had a similar problem and discovered that the fuel line shut off valve was defective. When I opened the valve the two holes did not line up causing a partial blocked fuel line. The car would idle and run down the road when I went slow but when I tried to speed up it would buck, jump and stall out. I would wait a minute or so then it would run again. The pause allowed the carb to refill with fuel so I could go again.

Do you have a modern fuel filter installed?

If you do, that is your problem. Take it off, throw it away, and install the original $80 sediment bulb & screen if you don’t already have one.

Bob, ... Between us ( MTFCA )and your Facebook post, have you come to a solution of your problem?

Did you check the sediment bowl's filter screen?
Ideally, remove the sediment dowl. Look for blockage in the inlet, valve position when on & screen.

Bob,
What size fuel line are you using?
Is there a shut off valve in the line?
Is so, that tupe?
Keith

I agree with those who think it's a fuel delivery problem. Those are the classic symptoms of fuel starvation.

Jugster wrote: ↑

Tue May 06, 2025 12:17 am

Thanks for all the replies. The surging would indicate a fuel starvation problem. I have no filters and no fuel pump; I'm just gravity-feeding as per original configuration. I think the next step is to check the gas-cap for venting (but it won't be that), then pull the fuel tank out of the car to have it cleaned out. Because of the baffle, I can only see part of the bottom of the tank. Because of the stalling in 20-degree weather, I don't think the problem is vapor-lock, but it wouldn't hurt to insulate the fuel line and exhaust pipe.

You do have a filter. When you de-solder it you might notice a very narrow edge of cap was rolled over the screen then soldered. Save time just use RTV to hold it in place

Are you running a hot air pipe?

Dan Hatch wrote: ↑

Wed May 07, 2025 1:46 pm

Are you running a hot air pipe?

You might be making carb ice even with the hot air pipe.
When it bucks and stalls, open the hood and look to see if your carb and intake are wet on exposed outside surfaces. If wet, you have ice.

Drive it with the fuel cap loose. I'll bet the problem is gone.

Ed, that fixed it for me once, in 1992 on our way to national rally with two couples from Spokane travelling with us. One of them generously refilled the tank on my buckboard we were driving to the event. We spent the next 50 miles trying to get the car to run properly. Eventually, on about our fifth stop, i lifted the fuel tank cap to check the level. Because I was using an English Ford script unvented radiator cap as a fuel tank cap, it should not have been screwed right down, but run loose. If the standard cap is used, that fine little vent hole is all that is needed, so long as it is not blocked.

Allan from down under.

Some of the modern fuels will get thick like varnish if they set for a long time. This can clog the fuel line. Try disconnecting it at both ends and run a wire up and down through it and then blow out with compressed air. This can help, Another common problem is condensation in the gas tank during humid weather. This will put water in the fuel which will settle to the bottom of the tank. So it might be helpful to drain the sediment bowl and then see if it helps. On one tour we stopped about half way to fill up the gas tanks. There were two gas stations at the location. Those who used one station had problems but those who used the other station fan fine. Mine quit a mile or so from the station and I drained the sediment bowl. After that it ran fine. Others who used that station had problems too. The underground tanks at the station must had water in them.
Norm