fuel pressure

[krakoosh]

I have an '03 5.4. I had to repair the relay in the fuse box but before that the pump was replaced, bad job of troubleshooting for sure. I now have a lean condition and mechanic says he's only getting 38lbs at the rail. The pump has been in since January working just fine. Problems started about 1 month ago with a slight miss that felt like the transmission slipping. It started to take a hair longer to fire up and finally threw PO171 and PO174. Replaced PVC hose assembly. It now takes considerably longer to fire up with PO171 coming back which is why I took it in for a look. He's saying bad pump. Has anyone ever had to replace the pressure regulator? Is that part a works or it doesn't item? I didn't check the pressure after new pump was installed so I can't say what it was at the rail then.
Just wondering if anyone has some idea where to go from here.

 

[Bedrck47]

When you replaced the pump Did you replace the fuel filter??

 

[Bedrck47]

Part 1 -Troubleshooting P0171 and P0174 (Ford 4.6L, 5.4L)

 

[Bedrck47]

http://www.expeditionforum.com/f42/about-egr-pcv-dpff-evap-iat-tps-maf-23583/#post191356

 

[stamp11127]

Good time to invoke the KISS method of trouble shooting. Verify fuel pressure is within spec first.

 

[Bedrck47]

5.4L 2V key on, engine off kPa (psi) 379 (55)
5.4L 2V engine running kPa (psi) 379 (55)

 

[docraymund]

You could check the fuel pressure regulator by attaching a hand vacuum pump to the vacuum port of the regulator. Or you could pull out the vacuum hose, wait a few mins. and watch if fuel comes out of the vacuum port which will indicate a leaky diaphragm. Also try cleaning the MAF semsor. It could also cause a lean condition.

 

[krakoosh]

When you replaced the pump Did you replace the fuel filter??

Yes. I'm going to try a new one in the morning as well...

 

[krakoosh]

Good time to invoke the KISS method of trouble shooting. Verify fuel pressure is within spec first.

He said he wasn't getting 55 but I need to see him Monday morning as I couldn't get there before he closed. I may go borrow a tester tomorrow and see what I get.

 

[krakoosh]

Part 1 -Troubleshooting P0171 and P0174 (Ford 4.6L, 5.4L)

I've read all that. Thanks for the link tho.