Car cold starts without issue. However after a drive, if left to sit for 30-60 minutes it's almost impossible to get the car to start again. Im wondering if its a thermostat, vapor lock, or something else all together. Any thoughts or suggestions are welcome.
Warm start issues
- Thread starter JBFury
- Start date
Vapor lock is a good possibility.
One way to tell is after car gets good and hot, then sits for 30-60 minutes, loosen and prop up the air cleaner housing. Get a couple of line wrenches (and not plain ole open-end wrenches) and loosen the fuel line to the carburetor.
If you have a couple of drips (or more) fuel run out, then vapor lock is most likely not the problem.
If you crack open that fuel line fitting and nothing comes out, then hit the starter a couple of cranks and check for fuel. If still nothing, then you do have "vapor lock" or fuel leak (or air leak in fuel line) somewhere.
BudW
One way to tell is after car gets good and hot, then sits for 30-60 minutes, loosen and prop up the air cleaner housing. Get a couple of line wrenches (and not plain ole open-end wrenches) and loosen the fuel line to the carburetor.
If you have a couple of drips (or more) fuel run out, then vapor lock is most likely not the problem.
If you crack open that fuel line fitting and nothing comes out, then hit the starter a couple of cranks and check for fuel. If still nothing, then you do have "vapor lock" or fuel leak (or air leak in fuel line) somewhere.
BudW
Aspen500
Well-Known Member
There is one thing that can be problematic on carbureted cars, depending on the car, temperature, etc. Modern fuel is formulated for fuel injection where the system is pressurized to at least 40 psi, (direct injection up to 2,000 psi). It tends to "boil" much easier than fuel did 30 or 40 years ago. That can give vapor lock or the fuel boils out of the bowl and basically floods the engine. We've all smelled it. Walk near a carbureted car on a hot day after it's hot soaked a few minutes and you get the raw fuel odor. That's because the fuel is vaporizing or "boiling" from the heat.
AJ/FormS
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But if the car starts fine in the morning, then the fuel has not evaporated or boiled off since you parked it last night.
as for the thermostat; it sets the MINIMUM cooling system temp and has nothing to do with the maximum. I get where your thinking is going, but I would try very hard to run the engine closer to 195 than to 160; on the minimum.
if your car is a mechanical lifter slanty, the first thing I would do is lash the valves.
If it's a 318, I would pop the hood when you shut it off and remove the air cleaner lid. Then I would sit there and watch and listen, for at least 10 minutes. If you hear the gas percolating in the bowl, and see the smoke coming up out of the carb, both together; there is your problem. That ain't supposed to happen.
as for the thermostat; it sets the MINIMUM cooling system temp and has nothing to do with the maximum. I get where your thinking is going, but I would try very hard to run the engine closer to 195 than to 160; on the minimum.
if your car is a mechanical lifter slanty, the first thing I would do is lash the valves.
If it's a 318, I would pop the hood when you shut it off and remove the air cleaner lid. Then I would sit there and watch and listen, for at least 10 minutes. If you hear the gas percolating in the bowl, and see the smoke coming up out of the carb, both together; there is your problem. That ain't supposed to happen.
LSM360
Well-Known Member
I think BudW and Aspen500 are spot on. Today's fuels are crappy for carbs and especially in Summer. My Power Wagon with Edelbrock 1406 (or is it 1408 can't remember now) takes several cranks to start when hot yet starts right up cold. Now if it sits more than about three days the fuel will evaporate from the bowls and then I will have to poor gas down carb. You might have better luck with higher octane or an Ethanol Conditioner additive.
LSM360
Well-Known Member
If Eth free fuel is gone within 48 hours you must be talking about a carb with really small fuel bowls!
I don’t have this hot start problem with my car at all.
Starts first crank cold with a half pump of the gas pedal, starts first crank hot without the gas pedal if it’s been sitting under a hour, over an hour and, I’ll have to give the gas pedal another half pump and it fires right up. Never have to crank on it a bunch though.
Starts first crank cold with a half pump of the gas pedal, starts first crank hot without the gas pedal if it’s been sitting under a hour, over an hour and, I’ll have to give the gas pedal another half pump and it fires right up. Never have to crank on it a bunch though.
Same here. Vapor lock can happen, but the cause has to be found. There isn't a "bottle of stuff" you buy for this. It's usually heat or really lousy fuel quality. Fuel line routing, size and quality can make this an issue too. If you do have vapor lock you need to find out exactly where the vapor is in the system. Rerouting a line or wrapping it in the silver spark plug insulator sometimes helps, or a different diameter line. Find it, as others have said.
Aspen500
Well-Known Member
Whether the fuel has ethanol or not, the point at which it vaporizes when not under pressure is much lower than it was 30 years ago. Ethanol free is best in a carbureted vehicle but even with it, it's less than 10% ethanol. Testing in this area always comes up with 6% at most, with some actually 0% but it says on the pump "MAY contain UP TO 10% ethanol". May contain none. Only way to be sure of course is buy ethanol free. Don't know about everywhere in the country but here premium (91) is always ethanol free and some stations have ethanol free 87 also.
A thought (look out, lol) is your heat riser valve stuck shut? That will cause all sorts of grief in hot weather by super heating the carb base, especially if it doesn't have the thick base to manifold gasket to help insulate from the heat.
A thought (look out, lol) is your heat riser valve stuck shut? That will cause all sorts of grief in hot weather by super heating the carb base, especially if it doesn't have the thick base to manifold gasket to help insulate from the heat.
That's a good question and I could use the guidance on where this is located and what to look for.
Couple of things reading all these responses:
1. I may try an ethanol additive, can't hurt. Better yet I may try and find ethanol free around here if I can. See what happens.
2. I've read a lot about getting a thicker gasket for the carb to help with heating issue and may do this as well.
3. I appreciate all the feedback. Seems to have triggered a lively discussion and as such, is one of the many reasons I dig this forum.
If you have vapor lock an additive won't help. Take a serious look at your fuel lines. If you really think it's the carb, a plastic 3/4" spacer may do it (If the carb is getting too hot). We did this a lot in Quadfrajets where the achilles heel was the float bowl boiling. You have to narrow down the actual problem though. A bottle of stuff isn't going to resolve it. I know that's not what you hope to hear, but that's real life. You probably have a line too close to the engine or something like that. And yes: the fuel these days vaporizes at a much lower point. Its not an issue in fuel infested cars.
Just a side note, and I doubt if this info helps but they have really good (And very expensive) fuel at the yacht club. It's basically racing fuel but I can't think of a way to get it into a car. They have it way out on the piers on a big cart with a credit card reader. The drag strip sells it too.. I guess if you had a smaller boat, you could fill up and then go to the paved boat ramp and trailer it then pump it from the boat into your car but that's way too much work. The fuel started to go to crap after about 1970-1971? I remember people sneaking airplane avgas from North Island and Oceana but that really wasn't good for their cars.
Mikes5thAve
Well-Known Member
Probably easier for that to use a outboard type gas tank instead if dragging a boat all over just to buy gas.
Mikes5thAve
Well-Known Member
Warm start could easily fall again on carb or choke problem. Boiling gas out of the carb or evaporating would also have an effect on cold starts. If you try to start it 5 or 10 minutes after the drive does it have problems? After an hour it should be cooled down enough to not have problems. How long of a drive are we talking about? Short trips or 30 minutes to town or stuck in traffic type situations?
Most drives are 15-20 minutes into town. Occasional highway drives for fun. No issue turning it over after a short sit of 5-10 minutes. It seems to be 30+ minute sits that replicate the issue. Now, I am still able to get it started after some pumping on the gas. Sometimes it'll turn over first try, but stall out if I dont hold the rpms for several seconds.
Mikes5thAve
Well-Known Member
When you're at the 30 minute time before you try to start it pull the air cleaner off and move the accelerator by hand and see what the choke does and if you can hear it squirting gas. It sounds like the choke could be starting to close causing problems but if you don't hear the gas squirting that's a problem too.
LSM360
Well-Known Member
I was not talking about a "bottle of stuff" for vapor lock. I was talking about a Ethanol conditioner for easier starts, less evaporation. If he discovers he has vapor lock he will have to fix the problem. Possibly adding electric pump. Carb spacers can be helpful.
