Hello there. Starting this thread as this issue seems to be wide spread but I want to be as thorough in describing it as possible. I've a 2003 with the 3.0 FFV engine, and almost 195,000 miles. Truck's been great but in the last few years P0171 and P0174 have been intermittently popping up and I've been going through changing and fixing things as they arise. I will list below said fixes. In December of 2019, codes were present and it was recommended I replace the Fuel Pump Assembly. I went cheap and bought a Spectra from Rock Auto. Recently I replaced that Fuel Pump Assembly under warranty twice for two separate problems unrelated to P0171 and P0174. I found an unused Motorcraft FPA on eBay, replaced it, and in a few weeks P0174 came up with a pending code for P0171. Took it to a shop today for some routine maintenance and asked for a smoke test and a fuel pressure test. No vacuum leak was discovered, however my fuel pressure tested at 30 PSI. I asked the tech if it could be the injectors or maybe a clog in the line, but he believed neither were the cause. He recommended seeing if the FP Assembly was still under warranty. Any advice is appreciated. Thank you.

• A faulty fuel pressure regulator/damper - CHANGED
• A weak fuel pump - CHANGED
• A clogged fuel filter - CHANGED
• A dirty or faulty mass air flow sensor - CHANGED & CLEANED
• Faulty oxygen sensor - CHANGED
• Leaking positive crankcase ventilation (PCV) valve - CHANGED
• Clogged exhaust gas recirculation (EGR) Port - NOT ON THIS MODEL

 

Welcome to the forum

3rd party fuel pump assemblies will often fail in the first year, some only last days
So yes replace it under warranty
And keep the DATED receipt because you may need to replace it again
All electric fuel pumps can generate up to 90psi

In a 2003 Ranger there are TWO things on the fuel pump assembly that can cause 30psi pressure, should be 55-65psi
The fuel pump, of course, could be leaking so can't build pressure
But there is also a Fuel Pressure Regulator(FPR) about 1/2 way up on the assembly, its round with metal center and two hoses

You fuel filter has 3 hoses, in from pump and out to engine like all filters
The 3rd hose runs back to the tank and to the FPR, the FPR is set for 55-65psi so when pump is on the FPR allows fuel to return to the tank to maintain that 60psi average

If its broken then you could end up with 30psi same as if pump was broken

The 1998 and up Ranger computers calculate air/fuel mix based on RPMs, load, injector size(lb/hr) AND fuel pressure at the injectors
Rangers have no "fuel pressure sensors"
1998 and up use 60psi as expected pressure, so if computer opens an injector for 100milliseconds it knows EXACTLY how much fuel will come out at 60psi
If pressure is below 45psi then computer will have to add more fuel based on O2 sensor feedback, i.e. Lean Burn
Same as if there was a Vacuum leak, extra air throws off computer calculations, same as less fuel flow

 

Thanks for the welcome, RonD! You seem a prominent presence on this forum, and I appreciate the help.

CEL came back on today with both of the lean codes. If either the pump or FPR are faulty, am I looking at replacing the whole assembly again? I haven't checked any of the local auto parts stores so I may be in a pickle if I can't score another Motorcraft.

Also, is there anything else that could cause the low fuel pressure? Something I remembered today was the previous assembly replacement was due to a faulty fuel line connection on the assembly that was causing a P0442 EVAP leak code. In an attempt to fix that, I duct taped the hell out of it, just to make sure it wasn't a loose gas cap causing it. In the meantime the lean codes returned. I cleared them, and eventually that EVAP code returned, which lead to my search and purchase of the Motorcraft FPA since I knew what was casuing that leak and aI figure the lean codes might have been associated with the P0442 code.

 

The Pump and FPR set the fuel pressure, only other thing that could lower pressure is a fuel line leak, and you would smell that, or a stuck open injector and you would get RICH code and smoke out the tail pipe

EVAP system is separate, it just puts in a slight negative pressure in the gas tank to prevent gas FUMES from escaping and polluting the air
If EVAP valve was stuck open it could cause a Vacuum leak situation and "maybe" a lean code, but a long shot on that, more likely to just cause a high idle after warm up

No, the 30psi is the issue not any other system

 

Copy that, and thanks again. Any recommendations on a replacement brand that isn't a Motorcraft? The internet isn't yielding any search results.

 

There is no other brand that's tested, so just pick one

If you have a local parts store then ask them what brand gets returned the most
I would recommend using a local parts store that stocks the brand you choose, to make warranty return/exchange easier if needed

 

Hello again. I finally replaced that fuel pump assembly, and just in time as the old one appears to be shot. However it's been a week and my Check Engine Light just came back on with the lean code. I had a feeling it would since the truck seemed to still behave the same: no real get up and go while accelerating, and intermittent rough idle on start-up that clears fairly quickly(usually when I've made several short trips in a close window of time). I haven't performed any tests, nor have I had it checked out by a professional. I was praying this new assembly would be the solution. I'm this close to going to the dealership and asking their crew what's the problem.

Assuming it's not any of the parts on the assembly, is there anything else I can try? Maybe the damper on the fuel rail?

Thank you in advance!

 

Get a vacuum gauge and test for clogged exhaust
Hook up gauge
Start engine
Idle should show 18-21" of vacuum and steady
Raise RPMs to 2,500 and hold, vacuum will drop and then come back up and stay up as you hold RPMs steady, if vacuum is slowly dropping you have clogged exhaust
This also causes Lean code(s), because oxygen can't get out

Check vacuum line on Damper, if there is no gasoline in it then its fine