so; the parents truck is basically stock; stock plate slid a wee bit and a mild tune on the AFC. the truck will randomly die like the key was turned off. i dont know if it does it just at idle or running down the road. but my dad said it'll run ok part throttle, roll into it wont seem to do much more, then he'll back off again and it'll actually act like it has more nuts. sounds like fuel pressure to me. as for the random shut off it did it today, had him pop the hood and looked at the shut off solenoid. still sucked up; turn the key off it drops, turn the key and it sucks it up and holds it in just like normal operation. idle is slightly low but it doesnt "stumble" while in gear. doesnt stumble like its running out of fuel. lift pump is stock but not OE, its got some miles on it but it isnt too old. acts like fuel is cut off completely; not a slow die or drop in rpm and stumble b4 it dies. i'm also tossing around the idea of the overflow valve; kinda like the truck loses ALL fuel pressure all at once.

 

sounds like the mix isnt correct between fuel and air. and having a low idle can possibly do that.. you can bump up the idle slightly and see if that helps

 

Could be the OFV if its weak.
Could be a dirty fuel filter or prefilter at the lift pump.
Could also be something plugging the suction tube in the tank.
Could also be the fuel system is allowing air in it somewhere thus causing it to loose prime.

I'd start by looking at the fuel lines from the tank front looking for wetness.Then pull the boot off of the primer pump on the lift pump and see if its wet underneath which is a sign of it being bad and leaking fuel and allowing air in.Also unplug the factory fuel heater and see if the plug is wet,that is also a good place for air to get in.

Many things can cause what you describe,you have to eliminate them one by one until you find it......Andy

 

thanks for the insight andy; we've dropped the tank not too long ago; the basket is clean. we've had spare fuel lines sitting in our basement for YEARS so it may be time to put them on... i'll look into the lift pump (i believe this is the culprit as its been noisy for awhile and has randomly gotten quiet again) and we've NEVER messed with the fuel heater/ sediment bowl sooo i may look into eliminating it. and the fuel filter was just replaced when i put a new section of hose on the return line behind the filter housing. i havent had much time to diagnose the problem. just took a quick look and figured i'd get on here and see if i could be pointed in the correct direction prior to gettin dirty. thanks again