Potential causes for warm start difficulty

[NealW]

This week I gave my son and his fiancée their first ride in the 1911 touring that I just finished restoring. The temperature was in the upper 50s and it started and ran fine. After we got back from our drive, I shut it off so that they could take some pictures of it and to put the top down before putting it into the garage.

Normally the car starts on the first or second pull when warm on battery or magneto without priming. For some reason, this time it wouldn't start or even sputter after numerous 1/4 turn pulls. I did use the choke it once or twice after it wouldn't start after a bunch of pulls, but that didn't help. After that I decided to clear the cylinders of any excess gas by closing the mixture needle, opening the throttle, and pulling it over four 1/4 turns. After doing that and opening the mixture needle back up, the car started right up. It easily started after that.

I have experienced this once before on our 15 runabout and had to do the same thing to get it started. The 11 has a Holley H1 and the 15 a Holley G. Any thoughts on what might have caused this issue?

Thanks,

Neal

[TWrenn]

Some form of a vapor lock maybe?
My '13 started that little stunt the first year I had her, after stopping her to gas up, for all the longer it would take at the pump, she'd hardly start afterward without yanking my guts out, choking it, adding "extra" fuel on the lever. After that year, it only happened once in the last 5 years. Go figure.

[TXGOAT2]

It sounds like a mixture problem. Normally, an updraft carburetor isn't subject to hot flooding, but I suppose it can happen. Since choking did not get good results, and clearing the engine did, It appears that it was flooded. Underhood heat imediately after stopping the engine after a run could result in fuel boiling in the carburetor, which could lead to flooding. I would check to be sure the choke is opening fully. It could be something unrelated to fuel mixture, like an intermittent ignition switch. When starting a hot engine, opening the throttle about 1/4 open may be helpful. If you start on magneto, it's possible the magneto output is a little less when hot, due to the magneto air gap being larger due to expansion of parts.

[JohnM]

Yes, it sounds like your carb is running too rich for a warm engine. Double check your mixture needle adjustment. When parked, does your carb drip gas? If the float needle does not seat tight, over time it can over fill the bowl preventing one pull and free starts on a warm engine that we all love.

[NealW]

Yes, it sounds like your carb is running too rich for a warm engine. Double check your needle adjustment. When parked, does your carb drip gas?

It could have been a bit rich, although I leaned it out initially after richening it 1/4 turn to initially start it. No gas was dripping. It just seems odd that it would be running fine and after being shut off for 5 minutes at the most, not being able to start at all. Certainly clearing out the cylinders seemed to make a difference for starting it at least. I should also say that at the moment I don't have the hot air pipe on, but I haven't either for most of the time I've been running it recently. It was low humidity and am using "winter blend" gas.

The ignition is also fine. Rebuilt coils, clean and 0.030 gapped Champion X plugs.

Vapor lock could be a possibility. Perhaps choking it cleared it out, and then clearing the cylinders cleared out the excess fuel from that.

[TXGOAT2]

"Winter blend" is intended to vaporize more readily, so it might tend to cause hot flooding under some conditions. Once warmed up, leaning out the mixture a little more than normal may get better results, especially on mild winter days. When starting a hot engine after a short shut down period, it's often best to assume it needs no choking at all. If a couple of pulls get no result, or a just a kick or two, a single pull with the choke on would probably be sufficient. Of course, all cars are different, and weather conditions and conditions of use have to be accounted for. Setting the plug gap at .028 may be helpful.

[JohnM]

I have a 26 with an NH carb. After sitting warm for fifteen or twenty minutes then starting, it kicks and sputters with too much gas. If I shut the gas off when I stop for more than ten or so minutes, later it will start very easily on one pull. BTW I don't have a hot air pipe.

[Norman Kling]

I would suspect that you might have turned off the switch before the engine slowed down. Try pushing all the way up on throttle and spark first before you turn off when you stop the engine. That way it burns out the gas in the cylinders. If it is running too fast, you will draw in a gulp of gas before it completely stops turning which could flood the cylinders, especially if running rich.
Norm

[NealW]

I would suspect that you might have turned off the switch before the engine slowed down.

I did not move the throttle to slow idle before shutting it off, so that could have been a factor.

[otrcman]

Neal, People have already posted who have far more experience with model T's than I do. But here is my experience with a 1970's automobile.

I was having a problem where the car was usually flooded after a short rest, but then started up just fine after sitting overnight. What I eventually found was a leaking carburetor where the float bowl emptied itself within a few minutes after shutting down. The only way I could start it after a brief shutdown was to begin cranking with the gas pedal pressed to the floor to clear the flood.

My car was a downdraft, so that made matters worse. But with a modern electric starter I was able to clear the flood readily once I understood what was going on. Yours being an updraft wouldn't be quite so bad, but could still have a bunch of raw fuel laying in the venturi as you begin hand cranking.

My fix was to overhaul the caburetor.

[TXGOAT2]

Downdraft carburetors can really flood an engine. One that leaks gasoline after shutting off will flood the engine, then if the vehicle sits overnight, the carburetor will be dry and may cause hard starting for lack of fuel. Another way downdraft carburetors can cause trouble is after a hot shutdown, gasoline can boil in the carburetor and flood the engine. This often occurs in hot weather. Modern gasoline seems to be more prone to doing this. Air conditioned V8 cars were bad about flooding after a short stop in hot weather. The solution was to hold the gas pedal to the floor while cranking the engine, but some people preferred to pump the gas pedal and run the battery down.

[John kuehn]

I’ve found that if my T won’t start it’s usually something to do with to rich of a fuel adjustment after it’s warmed up. But as you all know it’s finding the sweet spot when adjusting the carb. One of my cars has a tendency to flood if it’s just past the sweet spot adjustment while the other car is just before the sweet spot adjustment! (lean)!

I’ve learned to idle down before I cut the switch off and that usually works for me.

I think that if we drive our T’s pretty often the problem isn’t as bad or not much at all. It seems that way for me.
Each car has a mind of its own I guess!

[TXGOAT2]

All Model Ts are alike, except they're all different.

[Allan]

Both the Holley H1 and the model G are plain old Ford issue carburetors, so down/updraft issues are irrelevant. The Holley H1 on my 1912 van is sensitive to the float level. Once I got it right, i I have had no problems since.

Allan from down under.

[Kaiser]

I would suspect that you might have turned off the switch before the engine slowed down.

I did not move the throttle to slow idle before shutting it off, so that could have been a factor.

You nailed it, I have several old cars from other owners that i do the maintenance on and a T and a '66 CJ5 and most of them have this trait in one or other form.
I think it has to do with carburetor development, the older the carb design the more prone to this fenomenon (and other nasty habits like vapour lock), the older the car, the richer they tend to run especially at idle.
At cold start they like to be really "wet" but on a hot start that is generaly a bit too much and leads to flooding and hard starting

[bobt]

My 1915 runs and starts GREAT hot or cold unless there are a number of people watching me crank. The more people, the more I crank. bobt

[tvw]

This ^^

[nicklm]

You might try using another carburetor, if available, and see if it has the same issues. Float level, leaking valves or air leaks may all play part in the gas issues. All seem to have a specific or different way to deal.
Good luck. Try dealing with another club member to borrow a carb, if you don' have one.

[Loftfield]

Exactly the same problem encountered on a 1910 Buick Model 10 with a Schebler Model D carburetor. After driving myself crazy fiddling with the carburetor, double checking the magneto, and wondering if maybe incorrect tire pressure was at fault (that desperate), the trouble was finally found to be vapor lock in the fuel line. Re-routing the fuel line completely cured the problem. On my Model T's I route the fuel line under the exhaust for the same reason, have never had a vapor lock on the T's.

[TXGOAT2]

Fuel lines need to be kept away from heat. Any upward arching bends that could trap bubbles should be avoided. Even small dents or any other added restriction can cause fuel delivery problems, especially in hot weather or in high alitude operation. Always check that the gas cap vent is clear if fuel delivery problems are encountered. Carburetor bowl vents must be kept clear, also.