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I'm betting on a torn o-ring on one of the quick connects between the fuel tank and the fuel pump allowing too much air into the fuel. With all that work you've already done, that's about all that is left.
What I would do right now is cut them off and install some fuel injection rated flex fuel line in their places and test drive. The rest of the quick connects can be left alone. They work great on holding pressure in, but are lousy at keeping the air out if the fuel is being drawn toward the pump.
If that fixes it, give consideration to doing the Hutch mod for even more improvement.
If it was a torn o-ring , wouldn't it be doing it all the time anytime the fuel was being sucked out of the tank? Just a thought?
If it was a torn o-ring , wouldn't it be doing it all the time anytime the fuel was being sucked out of the tank? Just a thought?
Not necessarily. When I first bought my truck and was learning about all this stuff, I took some fuel pressure readings at the cylinder head. What was happening at the time was the fuel was alternating between fluid and foam.
I was not able to get a perfect seal and there was a pretty good fuel leak as I was taking the pressure tests. It would change every 5 seconds between clear fuel and what looked like beer foam. Back and forth, fluid, foam, fluid, foam, fluid, foam, etc.
Ford's design on the quick connects deserves the Dunce Cap award IMO.