If you have a clean sound "sock" on the fuel pickup that should protect the pump. It serves the same purpose as the 100 micron filter before the pump. Personally I'd pull the pickup next and have a look see. If the sock is intact and is clean or can be cleaned, simply remove the filter before the pump for a test.

Summit does have the 100 micron filters if you really want or need one. A local speed shop, if there is one near you, should have them also.

I am going to try the 100 micron filter before the pump to see if it was a flow restriction there.

The only way to check the sock/pickup is to drop the tank. But, I still don't understand how that could be the problem. The engine runs fine in cool weather (anything under about 80*). This ONLY happens when it's hot outside. I still think it's a vapor lock/fuel boil issue.

Any restriction on the suction side of the pump can encourage vapor lock. Higher temps worsen the problem. The fuel in the tank is getting warm also as you run - if there is any restriction on the suction side it can start vapor locking.

If that rear mounted pump was putting out 5-7 PSI like it should it would push fuel up and overcome vapor in the engine compartment. If you still aren't positive, suggest you rig your fuel pressure gauge right after the pump. I bet it does the same thing you see at the carb.

For reference, I run a '47 Power Wagon. The original design fuel system has a long steel line in the engine compartment on the same side as the exhaust manifolds. Mine would vapor lock running down the road in hot weather and really lock up after a hot soak with engine shut off for 10-20 min. After shutdown, the only way to get her going was to hose down the long fuel line and fuel pump in the engine compartment. I installed an electric booster pump on the frame rail with check valve so the engine could run on its mechanical pump also. As a test, I ran it in hot weather with electric pump off. After 40 min or so it started cutting out. Flip the toggle to turn on the electric pump and it smoothed right out and stayed that way. As a second test, I let it hot soak for a while and tried to re-start without the booster pump. No go. Hit the booster pump and she started right up. I could smell the fuel vapor being pushed out of the lines but it started and ran fine. That's why I'm pretty sure a correctly functioning electric pump shouldn't be affected by engine compartment heat within reason.

The pump may be shot by now also as they don't like to suck vapor.

Also check/replace any rubber fuel lines on the suction side at least. With time and alcohol they can soft and get sucked shut by the pump. I had that problem on a brand F PU and it created the same symptoms you are having.

Rain today, wasn't able to do much. Used the cardboard over the radiator to force a shut down sitting in the garage. A buddy loaded me his infrared thermometer and I shot temps on the carb base and intake while running and after shut down (think I need to buy on of those things). Base of carb stayed at about 130* while running and at shut down. Warmed to about 135* after shut down. Fuel pressure came back after 20 minutes with carb temp at 128 and engine restarted. So, I guess that indicates that fuel boil is not the issue. That leaves me with flow restriction from the tank as most of you said.

Before I go through dropping the tank, I think I'll try a test. I am going to pull the fuel line off the tank and put it in a gas can. I'll also remove the filter ahead of the pump. If it still shuts down running from a gas can, I'll have to re-think. If it runs, I'll drop the tank, clean, seal and new sock. Sound like a reasonable plan?

I wouldn't seal the tank. I have seen all too many sealed tanks fail and create a mess. If your tank is contaminated just put a new one in they are relatively inexpensive

Are you going to take the tank out?

Well, you guys nailed it. Did the gas can test today and truck ran great even after the forced heat with cardboard in radiator. Ran it for several hours and never locked. Pulled the tank this afternoon and it was nasty. Looks like 1/4" of varnish inside. Ordered the KBS tank cleaner/sealer kit.

There was no sock on the pickup and the tube can't be removed, welded to top of tank. I am going to get a welder buddy to cut it out and weld in a new 3/8" pickup which can be serviced. I think I'll have him weld in a second 3/8" fitting if I ever want to do a fuel return line.

I still don't understand why it only blocked the line when the weather was hot. Maybe it was just getting worse over time and started to fail on a regular basis this summer.

Anyway, thanks for the help, you guys are the BEST!

Great! For reference I have used the Eastwood 3 step tank cleaning kit on rare/expensive tanks. It uses strong detergent, Acetone and Muriatic acid to clean and a durable sealer. Worked well.

Fuel Cell