F150online Forums - Thought I'd seen it all.....

I've been dealing with Lightnings pretty much longer than anyone. And in my time, I've seen my share of pretty messed up stuff, both customer caused and factory caused. But what I encountered yesterday, takes the cake....

I had a local customer with an 04 come to the shop a few weeks back for some dyno tuning. Just a 4lb and an air kit. Put it on the dyno, loaded a tune, made a pull. A/F was in the 16s. Thought that was odd, but ok. Added 25% fuel, made another pull, mid 15s. At that point I told the customer something was wrong with the truck. Put a fuel pressure gauge on it, made a pull, and fuel pressure drops to 25 psi at WOT. It should hold solid at 50-60 psi.

I told the customer that fuel must be bleeding off somewhere, and since it's not leaking outside, it was most likely the hoses or clamps in the tank. The customer goes home and replaces the hoes and clamps in the tank for the pumps. He also changes the fuel filter. He comes back next week, we put it on the dyno.... same thing. I then checked the system to make sure it's switching to the high side of the pump voltage. Jumped out the high side relay and made a pull.. same thing. Now a little more baffled, told him that maybe one of his pumps was bad and he didn't have the volume to maintain pressure at WOT. So he grabbed a high volume pump it from me, and I also told him to replace the plastic Y connector with a metal one to rule that out.

He comes back yesterday with the new pumps and Y in the tank. I asked him if he check the fuel pressure at all, and he said no. So before putting it back on the dyno, I put a gauge on it and took it down the road. Still drops, just only to 35 instead of 25, since the higher volume pumps move more fuel. Now we are really stumped. I'm thinking if he's dropping off pressure, then either he's bleeding off fuel, or maybe his regulator is bad and not raising pressure with boost. I swapped out the regulator real quick with one I had here. Same thing. I asked him if he was sure he put the fuel filter in the right direction, and he said yes. I then jumped the high side relay once more to give that a try. Fuel pressure at idle jumped up so I know it's working, took the truck out again, still drops.

At this point, I am just about baffled. I figure let's put the truck on the lift, and maky sure the fuel lines aren't crushed or kinked anywhere. I really didn't think I'd find anything, but I had nothing left to check.

I start looking at all the lines, and don't see anything wrong. I check the filter, and it's flowing the proper direction. Just for the hell of it, I pulled back the plastic convoluted tubing over the flexible sections of fuel line at the rear of the transmission.... WTF!!! I have never seen anything like this before. I'll let the attached picture tell the story. Needless to say, that was the problem and once I fixed it, now he's got 60 psi of solid fuel pressure.

The truck came from the factory like this. The return line was the same way....

http://members.aol.com/powersurgeperf/twisted.jpg