Apparently, 2003 was a transition year in 5.4 fuel system design

[texasscot]

My 2003 developed a persistent P1132 code indicating an overfuelling condition in Bank 1. There are various potential causes for this that I checked off one by one. I’m now left with the last thing which - a stuck open fuel pressure regulator in the fuel pump. I have 61psi at the rail at idle, which is way too high causing the injectors to push too much fuel at each pulse.
Apparently, 2003 vehicles started out with a single fuel line going to the rails, with a fuel rail damper located on the LHS fuel rail, with the pressure being mechanically controlled by the pump in the tank. This is what i have. Attached is a pic of the inside of the housing from the LHS fuel rail. It has no function in controlling fuel pressure, other than as a pulsation dampener (despite it having a vac line on it).
During the model year, there was a switch to locating a pressure regulator on the rail along with a pressure sensor. Doing AI searches causes results to flip flop between these two versions, as it tries to rationalize the situation, giving spurious information.
I've replaced the fuel pump twice in its 295,000 miles. I'd never had i thought about the fact that there must be two different fuel pump designs in 2003; one for the single fuel line, i think it's termed "returnless", with an internal fuel pressure mechanical valve, and one for the newer version. Have i used the wrong pump previously?
Based on some real AI digging, i find only Motorcraft, Delphi and Bosch came up recommended for my system. Previously, i just bought whatever "2003" generic pump was available (i'm generally cheap). Anyway, Delphi pump coming from Rockauto tomorrow.

TLDR; despite all my interactions with this fuel system, i've only just found out about the two different designs in 2003.
Am i the last to know?!


Edit to add this info from 12 years ago on another forum, and for Rangers. It's disturbing because it mentions 60+ psi.

"1998+ Rangers utilize what is called a "mechanical returnless" fuel system. These returnless fuel systems have the following characteristics:

(1) there is no return line running back to the fuel tank from the fuel rail;
(2) designed to operate at higher fuel pressure - 64psi (+/-8psi);
(3) the fuel pressure regulator and check valve are now located in the fuel tank with the pump assembly, not on the fuel rail.
So then, 65psi fuel pressure is spot-on for your '98. It shouldn't deviate from that number all that much, even at different RPMS.
Did Autozone test for fuel pressure leakdown? You should verify that fuel pressure remains within 5 psi of the operating fuel pressure for 1 minute after the fuel pump is turned off.
The fuel rail "pulse damper", located on the fuel rail, reduces fuel system noise caused by the pulsing of the fuel injectors. It has nothing to do with controlling fuel pressure. The vacuum port located on the damper is connected to manifold vacuum to avoid fuel spillage in the event the pulse damper diaphragm were to rupture. As such, vacuum does not control the damper in the sense that you infer. I don't know of a test for the damper itself, or whether a bad damper can cause a "no start" condition."

 

[AWAR]

Does gas come out of the vacuum hose on the pulse diaphragm? Maybe it is ruptured. If your car is only rich on bank one it is possible that you have a bad (leaking) injector on that bank. Have you watched the oxygen sensor numbers?

 

[texasscot]

Does gas come out of the vacuum hose on the pulse diaphragm? Maybe it is ruptured. If your car is only rich on bank one it is possible that you have a bad (leaking) injector on that bank. Have you watched the oxygen sensor numbers?

Thanks for your help.

It's a longer story. Apparently got a flashing CEL on the highway and the driver (it wasn't me so precise details hazy) pulled off. I went to the car and ran a P0300 code for random misfire. I then had crank no start so had it towed home.
Based on the code, and because i had no more information, i just went into "cure the random misfire" mode.
Parts are cheap and my labor is free so i fired the parts cannon and changed plugs, coils and injectors. I did change the crankshaft position sensor relatively recently.
I had fuel in the vac line off the damper as you mentioned, so i changed that also. Except i changed it for the wrong 2003 part, which had two o-rings. Hindsight is a great thing! Why didn't i think "this part doesn't look right?" lol. A new proper one has arrived today.

I changed all the injector and coil plugs that had lost their clip function too, around 6 injectors and a couple of coils.
It now fires up but smells rich and throws a P1132.
I changed the pre-cat oxygen sensors. i'm reading around 3.7v at idle, and STFT Bank 1 read OL- fault. It won't go into closed loop.

I also did extensive smoke testing and did find a couple of vac leaks. Weirdly, the biggest one was at the brake booster/master cylinder connection where corrosion had crept under the rubber square seal. No leaks at exhaust or intake manifold.

I did a pressure test at the rail and it doesn't hold pressure properly after key on, key off. It starting dropping off almost immediately. I believe that's a faulty check valve in the fuel pump. While idling in open loop it sits at 61psi. Again the data is really mixed up on the internet. Some places say it should be 45psi and others 60. I couldn't find one coherent end to end data source for this non-returnable damper-fitted system. All the sources wove back and forth between this and the subsequent return system. it's very confusing.

i'm not now sure if i've fixed the original problem and introduced a new one! I got into pump specs and then explored injectors. Are the ones i bought over rated and dumping in too much fuel?

Where i'm at today, and my best guess at next steps: Delphi fuel pump coming and I'll throw that in Monday. I've switched back to the old injectors. I'll fit the new damper. I'll check the fuel pressure at the rail at idle.

I'll report back! Thanks again for your help.

 

[texasscot]

For completeness: New Delphi fuel pump fitted today, along with new fuel rail damper, fuel filter, and back to original injectors. Truck now goes into closed loop and no codes. For info, fuel rail pressure over 60 psi key on and at idle. Key off and fuel rail pressure now holds at 60 psi for at least a few minutes. Old pump had definitely lost its check valve function but to unclear why that really matters. I have no idea what the problem was and what fixed lol.
Proper road test tomorrow.