2003 5.4L 4x4 - Fuel Feed or Return Line?

[Eric M]

I'm asking this because the Hayne's manual lacks this information and because I have seen contradictory information on the internet. Some sites say the fuel pressure regulator on the fuel rail is directly connected to the feed line, others say the return line is the one connected to the regulator.

So, my question: the fuel line that runs from the fuel pressure regulator back to the fuel tank is the return or the feed line? I thought it was the return line, but I have doubts....

Thanks!

 

[Hamfisted]

On the '03-'04 there is just the feed line up at the rail. The return line is tied into the fuel filter inlet side. The thing up on the fuel rail with the vacuum line attached is referred to as the fuel pressure dampener by Ford. The actual fuel pressure regulator is attached to the fuel pump assembly in the fuel tank. Also there is a check valve in the assembly to hold fuel pressure in the line when the pump shuts off to make for easier starts. This check valve has been known to fail around the 150k mile mark and will result in hard starting and prolonged cranking. Prior years did have a return line up at the fuel rail, but Ford changes things from year to year just to keep you guessing.







Note the pressure regulator below the spring ....

 

[Eric M]

On the '03-'04 there is just the feed line up at the rail. The return line is tied into the fuel filter inlet side. The thing up on the fuel rail with the vacuum line attached is referred to as the fuel pressure dampener by Ford. The actual fuel pressure regulator is attached to the fuel pump assembly in the fuel tank. Also there is a check valve in the assembly to hold fuel pressure in the line when the pump shuts off to make for easier starts. This check valve has been known to fail around the 150k mile mark and will result in hard starting and prolonged cranking. Prior years did have a return line up at the fuel rail, but Ford changes things from year to year just to keep you guessing.







Note the pressure regulator below the spring ....

Perfect. Thanks a million. One follow-up question: Does Ford consider this to be a "return" or a "returnless" fuel system? Normally a "return" system would have a line from the fuel rail back to the tank, in addition to the feed line. The system you describe (which is the one I have) has a fuel return function, but not the "normal" kind. My fuel pressure is at 58psi which is way too high for a "return" system, but in range for the "returnless," according to the specs listed in the Haynes manual.

 

[Hamfisted]

Well, it's returnless from the rail, so I would go with that. Are you having engine issues ? How old is the fuel filter ?

 

[Eric M]

Thanks for asking. I was about to say that I had a problem, but then I just replaced the fuel pressure damper, cleaned the PCM connections, reset the PCM, and the stuttering went away. Thanks again!