Hi,

1996 F150 4.9 with dual tanks. My front tank pump died. I tried finding a Motorcraft pump, but it looks like its discontinued and no NOS available, so I bought a Delphi pump (FG0198). Truck ran fine, until the rear tank started filling the front tank. The Delphi's check valve had failed! Parts house exchanged me without issue. Now, I'm getting P0171 and P0174 codes whenever I run the front tank. I checked the fuel pressures and I found:

Front Tank (Ford manual says 45psi to 60psi is spec).
36psi @ idle
35psi @ 2000 RPM
Disconnect vacuum to fuel pressure regulator: 35psi

Does it look like my front tank pump is again defective? Any other brands of pump I should try? I thought a Delphi would be a decent brand, but I guess not since I received two duds in a row now.

Here's the pressures from my Rear Tank
44psi @ idle
42psi @ 2000 RPM
Disconnect vacuum to fuel pressure regulator: 52psi

Rear Tank pump has about 30k miles on it and it is a Motorcraft pump that I replaced about 7 years ago. Does it look like I ought to also replace my rear tank pump? I don't get any codes when running off the rear tank.

Fuel Filter was changed about 30k miles ago (when I changed the rear tank pump). Should I also try changing the fuel filter?

Thanks in advance!

 

I think they gave you a V8 pump
They have a lower pressure spec than your 4.9 (30-35 psi lust like your readings)
After putting 3 pumps in my 04 Heritage, I resorted to putting one of my (expensive as hell now) one way valves on it
Look for one of these at the junkyard on a 1993-1995 truck
Or pay big money for one on Ebay

I still look for these at the junkyard when I remember to. Worth 300 bucks a piece on Ebay. (I give mine away) out now

 

The fuel pressure regulator is responsible for controlling the fuel pressure, not the pump. All these pumps are capable of producing over 100 psi, but the regulator reduces it to the book's specs. Since your other tank is producing book specs, the regulator is fine and your pump has failed or is not getting enough volts to produce enough pressure. The fuel selector switch on the dash has a tendency of burning out and reducing fuel pressure.

I'm not sure how the 04 check valve since it will further reduce pressure by causing a restriction.

 

That is what I was initially thinking
Those one way valves cause no restriction
Either way, replace the pump (again)

 

I will have to keep an eye out for these. I just noticed again that my rear tank is filling my front tank. Another defective fuel pump!

Where would these be installed on the 93-95 trucks? Are they placed on the pressure output right at the fuel pump? I'll have to take a peek next time I'm at the pick and pull.

 

The external check valve goes on the supply side of the pump. It's a band-aid fix for a failed check valve on the output side. If the shuttle valve on the return side is bad it will not "fix" your problem.

 

I hate to resurrect an old thread, but I wanted to share something for the next person.

1) In October I ended up sourcing a Bosch fuel pump for my front tank and it provided the correct fuel pressure for my 4.9. The two Delphi pumps that I originally put in did not provide the correct fuel pressure. In addition the check valve on the Delphi didn't work so when I used the rear tank, it filled my front tank.

2) The Bosch pump is part number 67000 for the front (19 gallon metal) tank. It is discontinued from Bosch. I found a NOS one from my local Napa and I was excited to see that it was Made in USA (vs the China made Delphi pump). I opened the Bosch and found it had a Walbro pump inside. I blew into the tubes and it looks like the check valve and shuttle valve was functional. I installed it and my gas mileage improved, fuel pressure was correct, my OBD codes complaining about the engine running lean disappeared, and it looked like the tanks weren't cross-filling. I was happy.

3) Fast forward to yesterday and I noticed that my rear tank was filling my empty tank. It looks like the check valve on the Bosch pump had failed. I'm going to have to look for those external check valves and hope that its only the high pressure check valve that has failed. If its the shuttle valve, I'm back to square one again (I didn't keep the original pump - I should have). If I'd kept the original I could just swap the pump motor.

4) For the check valves, there's TWO lengths of the check valves. See the photo in Post #2 from @manicmechanic007. Due to clearance issues with the bed, if you use the longer check valve, the hose kinks slightly and the hose rubs against the bed. I need to source the shorter check valve (which to my dismay - none of the local pick and pulls have). The shorter one is the one with the orange tag in @manicmechanic007's photo. EDIT - @manicmechanic007 just schooled me. The shorter check valves are for the lines with the plastic retainer clip. If your fuel lines need that special disconnect tool, you need the longer check valves.

Long story short:
If your fuel pump wasn't cross filling and it is just the pump motor itself that died - take it apart and only replace the pump motor. Find a Walbro pump as it seems to be the only one that can provide the right pressure. The newer pump assemblies seem to not have very well made shuttle valves and check valves - they all seem to leak and cross fill.

 

The longer check valve is for the metal lines (extra room to use the special removal tool)
The shorter ones are for the plastic lines with the removable retainer
If you put a short one on a metal line, you'll never get it back off without a cutoff wheel
Right, those try to kink the lines when installed
I bend the line coming out of the sender, when installing one, so it has more clearance to the bed

 

Oh man. Thanks for letting me know that!!! I've got the metal lines. I'll head back to the pick and pull and grab those longer ones and just bend the lines coming off the hanger/sender unit.