Problem starting

[twilder]

I have a very odd thing going on with my A and hope someone here could help. I have a 1930 Coupe, rebuilt the carb about a year and half ago. Starts and runs great, I can drive it for hours with no problems. If I shut it off and leave it outside (it's been extremely hot and humid here)in the hot sun, it will not run! if fires for a few seconds, but quits as if it's not getting any fuel. I have replaced the pencil filter in the tank, took fuel line loose from carb and fuel comes out, but it will not run! It seems to only do this after leaving it in the hot sun. I know this sounds crazy, and I've been told to just park it in the garage all the time, but I'm afraid it's gonna get me out somewhere and I'll be stuck. Coil has also been replaced. I'm at my wits end trying to figure this one out. Any suggestions? Float sticking in carb maybe? I didn't replace the float when I rebuilt the carb.

[Big hammer]

It sounds like you have posted the first no hot start of the summer! You could use the search here or try what has worked for me. When I’ve had a no hot start I’ve pulled the choke and crank it 3-4 turns of the engine! It may sound funny but it has worked for me, also with my lawn mower after it’s hot and I shut it off to pick up sticks or whatever, it will crank and not start unless I pull the choke, when it roars to life (the A or mower) release the choke!

[alexiskai]

In general these are usually "heat soak" problems. When the car is switched off, the cooling system's action stops, and the residual heat from combustion, plus a hot environment, can heat up components that were previously being kept cool. Vapor lock is a type of heat soak problem. Sounds like you already considered the coil as a root cause.

How long do you have to leave it before it'll start again?

[twilder]

Thanks Hammer for your response. I have done the exact same steps you mentioned, however it cranks, will fire, and then quits as if it’s not getting fuel

[twilder]

I’ll usually let it sit a couple hours and It’ll fire back up. It happened today around 1:00pm. It’s still sitting in my yard in the heat and sun (3:45pm). I tried it around 2:30 and it done the same. I’m actually going to try it right now

[twilder]

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Just fired it up (3:50pm) started right up, ran great! Put her back in the cool garage. I have no clue why it does that. It’s happened to me all summer!

[Benson]

Do you still have WINTER Gasoline from last year or old gasoline in the tank?

If so drain tank and put in some FRESH summer gas. Not some which has been sitting in a gas can.

Winter gas boils at 90 or 100 degrees.

Summer gas boils at 140 usually.

If you have winter gas then it is "Vapor Locking". (Boiling in the 90 degree heat)

Boiling gas turns to vapor and carbureator can not work with vapor.

[alexiskai]

One thing you can try, if you have an assistant: the next time it happens, have your assistant start the car. When it starts to stall after a few seconds, spray starting fluid into the carb intake. If it catches and runs a little longer, the problem is in fuel delivery (vapor lock). If it has no effect, the problem is probably electrical.

[Benson]

Also today's gas if more than 3 to 6 months old goes bad.

I have put old gas in the lawn mower and it will not not start.

Sometimes you can pour some on the ground and drop a match in middle and it will not even light off.

[twilder]

I know this probably has to be a fuel related problem because of the ease of it starting back up with no problems. You mentioned a “heat soak” as a possibility. Is that the same as vapor lock? I had an old VW beetle years ago that did something similar. I was told then that “vapor lock” was a myth. Would maybe a heat shield of some sort be an option to give some separation between the carb, fuel line and the hot manifold? I have heard that heat sometimes will cause the fuel to “boil” in the fuel line creating air pockets

[twilder]

I have put fresh fuel in since the winter. Most recently about a month ago. It probably still had some old winter gas in it, but very little. I have driven it quite a bit since spring with no problems. Just started happening when the weather got hotter and I leave it out in the hot sun. Maybe she’s spoiled! I do keep it in a climate controlled garage

[nkaminar]

Next time it happens put some ice on the fuel line. You can just get a zip bag of ice chips from the frig. Also the carburetor.

[Marshall V. Daut]

Next time you stop the car in the heat and then go back to start it again, loosen or remove the gas cap temporarily. If you hear a WHOOSH!" from inside the gas tank, that's air entering through the filler hole. The engine may start up. With a gravity flow system like in a Model A, there cannot be air trapped in the tank, which happens on a hot day with a gas cap, whose vent hole is blocked. Check the gas cap to make sure someone hasn't put a radiator cap on instead. A radiator cap has no vent, so on a hot day, that could interfere with fuel flow to the gas tank. Once the gas tank and air inside cool after sitting for a while, the fuel will flow again to the keep the engine running. The reason your engine just barely starts and then dies is the result of a only trickle of gas reaching the carb. It won't be enough to keep the engine running.
Your description hints at a fuel delivery problem. It sounds as though you have taken all the right diagnosing steps. But try loosening the gas cap before you start the engine next time and see if that solves the problem.
Funny, how we don't see this complaint in cool or cold weather! Summer arrives and we begin seeing postings about this condition. There MUST be a connection...
Marshall

[1crosscut]

I am thinking heat sink after shut down is causing issues in the fuel line.
In really hot weather I have had similar issues.
Now when the weather is hot and I will be starting again in a short period of time I shut off the fuel and let the engine run until it starts to stumble before shutting it off.

This way a fresh cool charge of fuel fills the gas line and carburetor. Never have had a problem since doing this.

[Mike Peters]

Is your ignition coil wired correctly? The positive coil terminal should go to your ignition switch on the dash. In a positive ground system, the positive side of the coil must go to ground, which is the ignition points. I had this happen to me once, when the negative side of the coil was running to the ignition switch, the car would not start when hot. I reversed the wires and no more hard starts when engine was hot.

[twilder]

Thank you all for your postings. I’m gonna try it again today using some of your suggestions (suppose to be another hot day). I too feel it’s a fuel delivery problem on hot days, as I don’t have this problem in cooler weather. I even thought about maybe trying to insulate the fuel line somehow, just haven’t figured out the best way to go about that yet

[Patrick L.]

It sounds as if you're suffering from the dreaded myth of vapor lock.

Make sure the fuel line travels/pitches downhill the complete way.
A heat shield from the rear carb bolt to the exhaust manifold clamp also helps.