I finally drove the truck all the way to town today for the first time.(13 miles)
Filled up with gas and the truck took a few revolutions to start, and then drove home fine.

Got to the driveway and got out to open the gate, ran fine all the way to the house (1/3 mile)
Putted around to my parking spot and the truck wanted to die, and I was smelling fuel, truck was
running very erratically by this time. Shut it down. Went out an hour later, would not start.
Engine spun fast, and it hit a couple of times but would not start. I figure it's got to be vapor
lock. The fuel line is routed the same as factory, under the clip on the valve cover. No inline
fuel filter except the metal one above the valve cover.

What is the best/easiest solution on these old I6 engines?

 

Sounds more like fuel bowl gasoline percolation. The gasoline boils after shutdown (rising engine heat as there is no coolant circulation), vents the boiling gasoline out of the carb bowl vent emptying the fuel bowl. The bowl is empty on re-start. Takes a while for the mechanical pump to vacuum draw from the tank and refill the carb bowl.

You checked when you smelled gasoline for any fuel leaks?

There is vapor lock, fuel blend separation, fuel percolation and water laced ethanol gasoline blend to contend with. Ethanol has a much lower boiling point compared to straight (E0) gasoline.

Easiest way out, electric fuel pump.

 

Thank you for the response, I use non eth fuel only. I'll try a few more times to start it next time. I plan un putting an offy 6227c on it soon with a 4v,
and a carb spacer with coolant running through it. That should help, for now how can I stop the fuel from percolating?
I'll start raising the hood after trips for now. I don't want to put an elect. fuel pump on it.

 

Please see this thread, with my over-inflated opinion in post #3:

https://www.ford-trucks.com/forums/1...apor-lock.html

Specifically, see my comments about "vapor lock" versus "percolation". Both conditions are heat-related, but mitigation is different for each. Your symptoms certainly sound like percolation.

Not sure how to reduce the effect on the 300-6, due to the carb's proximity to the exhaust. Hopefully some others can chime in with suggestions.

One quick thing you can try is switching to a different brand of fuel. Despite all brands supposedly meeting standards for heat resistance, I have found some brands much better than others. There is a reason some brands are substantially less expensive.

 

I'll try that, this latest fuel I bought today was just shy of $.4.00 a gallon. There are several choices here for non eth.
Is there a fuel additive that might help?

Thank you F O T

 

Long thread here, but well worth a read:

https://www.ford-trucks.com/forums/1...apor-lock.html

Some people have reported good results mixing a small amount of diesel into the tank. Might be worth a try.

 

Well, the actual main reason that your application experiences this is the intake and carb being mounted right at the exhaust manifold. And this happened (vapor lock) well before the advent of ethanol laced fuel.

You first need to (IMO) mount the carb on a phenolic spacer and possibly insulate the pump to carb fuel line to prevent heat absorption. Even the mechanical pump draws heat from where it is mounted. DO NOT run any type of coolant flow through a carb spacer.

The ACL itself acts as a tent holding engine heat around the carb.

You might try leaving the hood open after shutdown to dissipate heat more quickly and see if that helps (it will isolate the problem).

Maybe next time you fuel, take a mason jar and fill it about half way. Sit it on the counter for a day or so and see if there is any separation (water). The fuel source may be fouled.

Can you post an under hood photo?
Here is a 'quickie' TECH ARTICLE - https://www.truckofmine.com/what-is-...it-altogether/

 

NEGATE the phenolic spacer -




SOURCE - Order Products

 

I fought this on my 300 six and the only fix is an electric fuel pump on the frame. Most vapor lock occures in the fuel pump due to hot engine oil and you have to push the fuel through. There is a great video on U-tube all about vapor lock on classic cars using carbs and modern fuel.

 

That is it right there, my truck does the same thing and if I sit at a long light when I take off I have had it die on me. The other day when it happened pulling the 20' trailer I see the AFR gauge go blank so it was way lean!
I run a heating plate under the log manifold and should remove it for summer. I run EFI exhaust manifolds.
When the fuel boils the vapor goes down the carb opening and floods the motor. If toy hold the throttle wide open it will start like it was flooded.

Now being you are still running the factor manifolds there is a butterfly in the exhaust manifold that points hot gases to the intake when cold and should open when motor is up to temp.
They get rusted pointing to the intake heating it so check this if it is working as it should.
Dave ----

 

I used to know several tricks to cut down vapor problems. A rubber hose split down the middle and slipped over the metal fuel line will slow heat transfer if you cover the line in the engine compartment. You don't need to cover it behind and away from the engine heat.. An electric pump in addition to, or in place of the factory mechanical pump. (Sometimes you get fuel vapor and the mechanical pump loses its prime) If your truck is equipped with a return line on the filter originally, make sure that is in place as it routes vapors back tpo the tank where they can cool and condense.

As for additives, I live near the Ohio river and noticed a lot of boat owners fueling up will add Stabile 360 ethanol treatment. I've started using that in my equipment and it seems to help. However, I can't say for SURE it works, just that I haven't had any issues like earlier equipment.

Now, in the past, I have used a WOODEN spacer under the carburetor. It has to be heavily varnished and cured to keep fuel from getting into it but it insulates and raises the vacuum just a touch to draw the fuel/air mixture in better. You can either make just the outer spacer or make it with the venturi holes in the middle. Find a phenolic one and make a wooden copy.

 

The HEAT RISER VALVE.

Usually you can wire it open for the summer and use it only for winter. (if spring actuated). Is it spring or vacuum motor?

I can't figure out why FORD designed the carb mounted over the exhaust manifold.

Now if you go to a 4V INTAKE, you will have more options as for heat shields.

 

The flathead 4 in my 1948 Jeep is the same way. Wasn’t the Dodge slant six like that, too? V8 engines, with no exhaust in close proximity to the carb, often had an extra passage in the intake manifold to warm it up.

Just a hunch, but I think way back then fuel chemistry was such that an engine ran better with the intake manifold warmed up a little bit. Maybe the fuel didn’t vaporize as easily, so a little extra heat was beneficial.

 

The HEAT RISER SYSTEM was used for cold outside air operation with a carbureted car (along with a choke). The valve would direct hot exhaust gases under the intake manifold carb plenum to heat the fuel charge as the fuel would separate from the air/fuel mixture at the bottom of the plenum and then pudding on the plenum floor. This would starve the engine of the correct fuel mixture.

Once the engine warmed fully, the valve closed and the fuel would remain in suspension in the plenum due to engine latent heat.

Now if the engine still has an operational EGR SYSTEM, it is adding even more heat -

 

Thanks for all of the help guys. How did Ford get away with these trucks having this issue off
of the showroom floor? (brand new) I'll have to take a dive under the manifold tomorrow.
I'll look for my previous under hood photos I posted.