Does anybody know if there is a one way valve made for our trucks fuel system to stop air intrusion? It seems to me it would be a good idea to be able to stop the fuel from draining back to the fuel tank.

 

The is one of sorts in the filter head, but it looks like it's fail prone with age:

https://www.ford-trucks.com/forums/1...l#post13225262

Not sure if that's 7.3 specific or not.

 

I was thinking something like a water line one way valve. I can't find any wet spots but it seems I"m looseing my prime somewhere. REplaced the return lines, all of them including the clamps. I'm wondering if these clamps might be a problem. I could understand if the hose was old and hard but the hose is plyable.

 

Some people have installed a squeeze primer bulb like boats use inline. It has a check valve (or two?), and if you need to prime the system you can save your batteries and starter using it instead of the engines lift pump.

 

I have an electric pump under the cab but still I'm looseing the fuel and can only guess it's going back to the tank. None leaking onto the floor and the fittings all seem dry.

 

check/replace your fuel line olives as well. there are four I beleave. one is all the way in the back of the engine on the hard return line. also check/replace the piece of rubber line on the suction side of your mechanical pump if you still have it ran that way. air intrusion can be a real mother to find.

 

I've come to the conclusion I don't have air intrusion. I drove it for over 10 miles and after I got home shut it off. I had the block heater on all day so it started already warmed up before I ran it down the road. I let it sit 2 minuets and tried to restart it. Turned over fine but didn't start. Even with starter fluid, no not either, it still didn't start

 

That sounds like hot pump failure syndrome.
Replicate this experiment, but keep a jug of room-temperature water with you.
Attempt to start it hot; if it doesn't start, slowly pour the water over the back side of the injection pump(just in front of the 8 injector lines).
Try to start it again. If it fires right up, your IP has too much internal clearance to build up pressure when hot.
You can fix this by either replacing the IP, or increasing cranking speed -- they both will do the same thing.

 

The mechanical fuel pump itself is a one-way check valve.

 

I replaced the original mechanical fuel pump with an electrical pump

 

Electric pumps /can/ have the check-valves fail(it runs, but doesn't pump).
My dad had a reasonably high-end looking pump on his truck the PO had installed; it worked great, until one day it just... died. the truck stalled, no fuel came out. But the pump was clicking, seemed to be working. I played around with it, and at certain angles it would pump, others it wouldn't. I'm guessing the check-valve broke somewhere inside it.
(my dad replaced it with another electric, and has had no trouble of /that/ sort since.

edit:
Personally, though, I'm of the opinion that a good mechanical pump is a better idea; I've seen way too many electric pumps fail at the most inopportune time. Plus, the mechanical ones are cheaper; you can afford to keep a spare with you if you are worried.
(Plus, at least in theory, as long as the engine is running and you don't have air in the lines, the IP should be able to suck fuel /through/ the low pressure pump... so if it /does/ fail, chances are it will fail on you as not starting, and not dying while running.)
I solved all my priming issues with a primer bulb. Cheap, dual check valves, and gives you a manual prime method should you run your tank dry and can't get it to work.