Fuel Starvation when warm at high throttle

[thecantaloupeman]

I'm currently having issues with fuel starvation. At first, I assumed vapor lock because my metal line was touching the block. I replaced the line with rubber temporarily and still had the issue. I replaced the pump because It seemed like it wasn't consistently spraying fuel. The issue persists still. Then I put a clear filter before the pump and replaced all rubber lines. Now I can see when the truck is cold my filter is full. As soon as the truck warms up fully, the filter is almost empty and I can see the fuel spurting every once and a while into the filter with a few air bubbles. Blocked lines maybe? I connected a boat tank with some rubber line before the pump and the issue persists still! So no blocked or cracked lines.

What gives? Can a carburetor needle and seat cause fuel delivery issues before the pump if it's getting stuck closed? The fact this is only happening when warm makes me think vapor lock still but the only thing hot near the lines is the lower rad hose and it is nearly impossible to not have the fuel lines touch it. And the fact that this issue appeared makes me think something had to change since it was driving fine a few months ago and the issue gradually got worse.

 

[fast 99]

Using a clear filter as a diagnostic tool really doesn't work. After dealing with defective fuel pumps twice, check the pressure and volume first.

There are replacement pumps out there made without the return spring on top of the pump arm. The arm will not return completely resulting in decreased stroke, causing low volume.

 

[BRetty]

I suspect your problem is a clogged filter/sock in the sending unit in your tank. You have to take the bed off and/or slide it back to access it, but it's worth looking in there and also swabbing the tank out with a kind of $10 "gas tank swiffer" you can get at AutoStore.

BR