Long story for a hopefully simple solution:

I have a 1990 300 six in a 73 f100. The 90 engine was already converted to non feedback carb when I bought the engine. The ignition system is a Duraspark II. I had to use an electric fuel pump since the '90 doesn't use a mechanical pump. I installed the electric fuel pump on the frame rail between the cab and rear axle.

Everything has been running really well, plenty of power, smooth running except 2 out of 3 times I run it it will stall after a little while. Generally when it stalls, I let the fuel pump run a little while and start it again. Most of the time after it stalls once, if it does at all, it will continue to run without problems.

Usually if it stalls it is within the first minute or 1/4 mile.

About a year ago I noticed that the fuel hoses that came with the fuel pump are total garbage and were disintegrating and leaking. I replaced them with new hose this spring. Over the summer it worked better but every once in a while it would stall, but if it did, it always worked right away after a running only the fuel pump for a little bit.

Over the weekend I noticed that the new hose is leaking too. I bought new 3/8" hose and put that on out at my parent's farm. During that process I leaked out a bunch of gas in the line. I also noticed that the hose I used seemed slightly too large in diameter but I clamped it down anyway.

Later that day when I was leaving to go home, I got toward the end of the lane and it stalled. I could not get it started again no matter how long I let the pump run. I cranked the engine a LOT during this time.
I walked back to the house, got Dad and we went to pull it back to the shed. I tried to start it and it did run briefly. I tried again and it ran. I drove it down the hill and left it run. I decided to try to drive home again since in the past it almost always worked fine after the stalling episode.

I drove it about 1.5 and was decelerating down a hill to a stop sign when KA-BOOM! The loudest backfire I have ever heard happened and the engine stalled. I sat at the bottom of the hill for a bit and wondered if I should even try to start it. I did start it and immediately noticed it was louder. I popped the hood and checked the manifold. Everything seemed fine there. I checked the muffler and it is bent all to hell.

It stalled one time out at the stop sign.

As I drove it back to the farm, I was switching the fuel pump off until the engine would stall and flip it back on right away and the engine would re-ignite. I parked it and it still sits at my folk's.
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Did that muffler explosion hurt the engine? What do you think caused it?

What do you think is causing the stalling?

 

I doubt if the muffler explosion hurt the engine. There would not be much that could get hurt.

Backfires usually occur when unburnt fuel ends up in the exhaust system. Most common upon deceleration. It is possible that your fuel line may have collapsed internally and is starving out the engine of fuel intermittently. Since the new line is already starting to leak I would go to a dealer that specializes in good hydraulic hose and get a premium hose meant for fuel. I had to do this after encountering this:

 

Did that damage come from a collapsing hose?

I forgot to ask earlier, what pressure can the needle valve handle on the stock 1 bbl carburetor? My pump was advertised to provide 4-7 psi.

 

Just guessing here, but the original problems might have been caused by the "poor quality" hoses provided with the electric fuel pump. Perhaps some trash made its way to the carburetor... do you have an inline filter?

On my 1986 F150 with 4.9L engine, the fuel line is 5/16", not 3/8" as you used. That may explain why you said the hose seemed loose and leaked.

If the fuel pressure is too great, you might want to install an adjustable regulator to reduce the pressure.

 

The damage was from long term use. It did not collapse per se (well, I guess you could say chunks of it collapsed), but it gave me some religion as far as using only the best quality hose I could find.

 

I think I better get a smaller line of higher quality and see what happens.

There is a bigger filter immediately ahead of the fuel pump. The hose between them is the one that leaks. There is also a small filter on the carburetor. I should check that, but like I said it runs down the road ok and has good power... but I'll check anyway.

Do you know what psi a mechanical pump would put out? I read somewhere that an edelbrock carb can only take 6 psi but that doesn't mean the little one barrel can't take more than that. I have never observed gas leaking out of the carburetor or other obvious signs of flooding.

 

What kinda electric fuel pump are you running? know it's specs like fuel flow and PSI?

I used a Facet Posi-Flo 60104 Electric Fuel Pump I picked up at a NAPA. Seemed to work well enough until I swapped to EFI. If you have high PSI efi pumps, you could use a Holley 12-803BP By-Pass Regulator to get the low PSI and utilize the original nylon fuel lines.

I've seen those nylon fuel lines survive and work even when the truck around them rusted away. Just not sure about them in -40* weather which is where I am... but whatever. Maybe use nylon fuel lines instead of rubber. They should survive ethanol as well.

Basically, it's all push together but can get proper couplings to interface with whatever you got. If something is tough, boil them in hot water to make it pliable enough to work with.

 

I believe the pump is 7 psi max and 35 gph. The engine is not efi.

Here is what the leaky setup looks like. I need smaller 5/16 hoses.

 

grasfarmr73,

Going back to the original post... you state that sometimes the truck runs great and then dies and if you run the electric fuel pump, sometimes it starts again. Well, with the loose [3/8"] hoses, not only do you have leaks between the fuel pump and the carburetor, but you are likely sucking air between the pump and the gas tank!!! Engines do not run well without fuel.

 

I hope it's that simple!