Nice weather now in northern Texas brings a heat problem. I’ve been having what appears to be a vapor lock problem. Runs great then if I shut it off it won’t start till I let it cool down. I’ve got stock 352 with stock 2bbl carb, newer mechanical fuel pump OEM style with built in filter. Fuel line is stock metal that runs up and over the water pump and across the manifold. All standard stuff. Hood does have a noise blanket. When it happens I pull the air cleaner and wait half an hour or so and it will start back up. Anybody have any experience with fuel line insulation or heat shield or fins? Still have stock tank behind the seat. Engine temp is fine, fan and shroud all good.

Maybe insulated braided flexible fuel line?
TIA

 

You’re sure its not the starter getting hot? As far as fuel lines, they do sell insulating materials for them...various designs. Some, you have to disconnect the line, some velcro install. I can’t say they are the ultimate solution because, although they may keep the heat out, they also keep the cool out. They may, in fact keep airflow off the line and delay cooling....not sure yet!

 

Do you have a carb spacer? I remember the big boys back in the day making them out of wood before we had access to order on line.

 

I don't have a carbed rig to try this on anymore (I mean, technically I do but it doesn't run), but maybe something for next time. I'll also add that he recommends a phenolic spacer in the comment section of the video.

 

It does have a carb spacer. I’m gonna see if i can determine if it is heat soak vs vapor lock. I’m thinking it is soak. I really haven’t had an issue, or at least a big one while running just restarting after sitting hot for a couple mins. Starter spins up just fine, got spark. I haven’t been able to peer down the carb during these episodes to see fuel yet.

 

If you can find any wooden clothespins clip them on the metal fuel line every 6-8 inches. It's an old trick to circumvent vapor lock in the lines. The clothespins act like a heat sink, pulling heat out of the metal line. It works!

 

I had an ignition coil act similar once in hot weather. Might try a different coil

 

I've discovered the truck will fail to start right after shutting it off so it isn't a pure heat soak after shut off issue.
I did get a chance to watch the accelerator pump squirts when the engine is off and hot and they look healthy.
I experimented with various methods to attempting to restart the engine. What I settled on that seems to work pretty well is a single accelerator petal press and hold then I can get it to cough back into life reliably.
Not quite sure where this leaves me. I am still going to insulate the metal gas line just cause it does get pretty hot and the engine does run rougher when hot so it can't hurt.

 

I would say it is heat soak.
You said you have a carb spacer is that spacer also a heat plate that you have heater hose going in & out of?
If so bypass this heat plate and just loop the hose together around it as a start.

Todays fuel blend is a lot different than it was when the truck was made, even for my 81 F100 with a 300 six.
The gas is made to vaporize easier and is not an issue with todays EFI motors but us old timer cars & trucks using carbs it is a big issue.
Also some places have a winter blend that makes it even worst when it get warm and we take the truck out and get gas before they get the summer blend in.

The heat soak will vaporize fuel in the carb and when it is out and heavier than air it fills the intake and floods the motor.
You can try and hold the pedal to the floor and see if that helps. It sounds like for you with the throttle open some it helps when starting.

The other thing I have heard but have not tried as I don't have a heat soak problem with my truck, is to make the fuel heavier.
To do this they say add some diesel fuel to a tank of gas at fill up.
If you add 20 gallon of gas to fill, add say a pint to start with and work your way up to a qt. I would say no more and half gallon to 20 gallons of gas.
Once you find the magic mix you should be set at fill ups.

BTW this seams to be a bigger issue with the v8 motors with the carb sitting in the middle of that big heat machine than the straight six guys like myself with the carb hanging out off to the side of the motor.
Dave ----

 

Have no idea if adding diesel will help with heat soak but every time I fill up I add a gallon or half gallon of diesel depending on the fuel level when I fill up for a top lube of the engine. After driving for an extended period of time and my pickup sitting for a while it was hard to start and holding the gas pedal all the way down to the floor does help me getting the engine started.

 

Are you using the 10% blend gas or the real deal?
Do you find it starts hot differently with 1 gallon or half gallon of diesel to how much gas?
Do you get any smoke out the exh. with either the 1 gallon or half gallon added to the tank?
What if you were to cut it back to 1 qt to see what that does on start up just for a test on a tank or 2?

I am asking because you are one of the first that is adding diesel to gas but for a different reason.
I would do it if I had issues starting when hot but on the 300 six we don't really have this issue.
Dave ----

 

Our gasoline here does contain ethanol and I haven't noticed much of difference between a half gallon or a gallon of diesel on starting.
No smoke issues at all up to a gallon but I can say that if you go over a gallon in the in cab tank you get the distinct smell of burning diesel from the exhaust and the plugs will foul out quicker.
Good question on cutting back and think I may experiment with that and report back with what happens. Can't say how definitive that would be in determining whether diesel helps with gasoline containing ethanol or not but it does have me wondering enough to check it out.
The diesel was recommended by a mechanic friend as an alternative to expensive aftermarket additives for engines without hardened valve seats back in the mid-eighties.

 

Wooden clothes pins is really old school but it sure does work. My '49 was very suseptable to vapor lock and adding an inline electric fuel just forward of the tank solved the problem.

 

Many years ago, in an old Mercury I had, after driving a bit the starter would heat up and become weak. If I tried to restart within a few minutes of shutting it off it would crank really slow with that brief surge of the crank. Became second nature to me in that would time a quick depress of the pedal at the surge. For me, started up every time. Anyone else would just kill the battery trying.
As far as heat soak is concerned, as others have suggested, hold the pedal to the floor and crank. Here in AZ have been doing that forever. Regardless of temperature, (mostly just habit) starts up every time. No doubt anyone else trying would just kill the battery. Think of it as a built in anti theft device.

 

I have used this procedure to start a heat soaked or flooded engine. do not touch the pas pedal and crank the engine 10-15 seconds, turn starter off. SLOWLY press gas pedal down about 1/3 the wayand hold it there. then start the engine. It works for me an my stock 352.