Since the OP has two tanks that work he could try Matthews diesel fuel additive in one of the tanks. Matt said 1 quart of diesel per tankful. That would be about 1 part diesel to 80 parts regular ethanol gas.

If that fixes the vapor lock issue be sure to post your results.

 

Thanks, Karl, Seems like I'm lucky my truck is EFI.

 

He has a 300 six and the exh runs down the right side.
All fuel lines run down the left side so any heat the line may get is from the ground up.

So I said remove the fuel cap but cant remember if I also said to change ALL OLD RUBBER FUEL LINES!
They may look good on the out side but bad on the inside.
Being it happens on both tanks the outlet of the switching valve hose could be the bad hose plugging the flow.
Just change all fuel ling hose.

Oh I could not pull fuel from a gas can up on the inner fender run to the fuel pump on motor when using 3/8" hose even with 2 clamps at the pump.
I even replaced the pump because of it.
When I replaced the 3/8 hose for 5/16" hose I was able to pull fuel from the can.
So the right size hose is a must!

I have dual tanks and 300 six on my truck, motor driven fuel pump and not have any problems.
I did replace all the fuel hoses when I rebuilt the truck 5 years ago.
Dave ----

 

You can thank our government for your truck being finicky with the fuel. They have messed with the fuel and it vapor locks easily.

My Bronco II was completely original, and the fuel tank and fuel line routing was completely original. On a hot day it would throw a fit and buck and jerk till I got moving down the road, As long as I was moving, it was fine. Once I stopped at a stop light or stopped and went into the store, leaving the light or leaving the store it would buck and jerk and sometimes stall out. I knew it was a vapor lock problem. I found where they ran the fuel line down the frame, and then ran the fuel line out of the "C" of the frame and up to the rubber line that went to the fuel pump.

1. I insulated the line right at that point by splitting a old heater hose and slipping that around the line. It did help except on the hottest days it still did it.
2. I then took the line loose,, and ran it over the frame at the rear, and ran the line on the outside of the frame, snuck it behind the suspension and back into the engine compartment. Helped again, but did not cure it when I parked at the store.
3. I then bought a cheap electric fuel pump. Mounted that in front of the rear axle on the frame, and then hooked that up and ran a new line up front. I went up high and skipped the original fuel pump. Problem solved after that.

 

Just a short update. Our truck is in the garage at our lake place so we "play with it" on weekends. I pulled the fuel line off at the fuel pump and fuel did not flow freely from the line. It should since the line was lower than the tanks correct? Took the gas caps off to make sure it vented This leads me to believe that there is some blockage in the line, the lines look fine with no kinks so it must be internal. The tank selector valve solenoid was also between warm and hot. Over the weekend we plan to pull it off, test it, and replace it, if necessary. We also plan to put small fuel filter in line prior to the selector valve. As long as we have the lines off, we will drain both fuel tanks and look at the contents to make sure there is not debris in the fuel.

 

I think Dave mentioned rubber fuel lines can plug on the inside. That could be your source. I caution about fuel filters on the suction side of mechanical pumps. That can add to vapor lock issues. Keep the stock filter at the carburetor. Yep check your tank. Old tanks are often in need of replacement.

 

No filter before the fuel pump and NO WAY that far back as it will just add to the lower pressure on the line and lead to gas boiling sooner.

Yes replace all rubber fuel line starting at the tanks all the way to the fuel pump.
I found I could not pull fuel if I used 3/8" hose for some reason went with 5/16" hose and was able to pull fuel.

I have the same fuel system as you, dual tanks with the 3 port switching valve, and I have not had any problems in the 5 years the truck has been on the road.
As part of my 4 year rebuild I replaced ALL rubber fuel line
I do have a hot restart issues but that is because the fuel in the carb boils and that has to do with todays gas blend not the truck.

As for not getting fuel out the line at the pump it may be below the tank but the hose comes out the top.
So unless there was fuel in the line to pull fuel out the top you will not get fuel.
I would put your money on replacing the rubber fuel hose and all will be good.
Dave ----

 

Well the solution in the end was........ a different fuel pump. Hard to believe that the one from the Ford Dealership was bad but replaced it and now we have had no issues. It was still good to replace all the fuel lines, rebuild the carburetor. I sincerely appreciate all the good advice and Ideas. The next two projects on the list are the Oil Pan gasket, which looks like and interesting project based on other posts and then replacing all the weather seals on the doors and windows! Thank you again for all your help

 

Was the pump in a Ford box?
There have been posts and I have had one being bad out of the box.
Most that I seen put out high psi. Mine put out 18+ psi before I turned the motor off and this was a non-Ford so it is not just for Fords

Good luck on the next 2 fixes.
I cant help on the pan gasket as I did mine with the motor out of the truck during the 4 year rebuild.

Weather strip see if you can find a seller think was Fair Child on Ebay.
Pretty sure that is who I got mine from and it fit great.
I also got the rear glass seal but have not used it or the inside window fuzzies. wanting to get new door panels.
Dave ----

 

I am assuming it was in a ford box as it was done at the ford dealership. I had my mechanic friend there do a once over to check a few things when I purchased it and had it changed since it was leaking. Thanks for the tip on the weather strip. I have heard some fit issues from others.

 

I’m surprised your local dealer even had a pump for a 38 year old truck. Just wondering if it had been sitting on a shelf all these years and had succumbed to old age before installation.

Even if they had to special order it for you, it may have been sitting on a warehouse shelf all this time.

 

It can be done in situ, but is not fun:

https://www.ford-trucks.com/forums/1...aight-six.html

My experience with a 351W:

https://www.ford-trucks.com/forums/1...y-84-351w.html

Obviously some details will be different. Do note my suggestion to put jack stands under the frame.

However you do it, definitely go with a one-piece rubber gasket. The stock multi-piece cork design is miserable to install, especially if working from underneath.

 

Thank you! Should be an interesting day....... even minus the beers.