P0171 P0174 yet again - please help!

[2000LXS]

I bent the rail up and I could sneak the pump bye with no problems just be careful not to bend anything taking it out of the tank.

 

[tlestan]

Sucess!!

OK, to follow up with this project, I actually just put in the new fuel pump tonight. 50 bucks for a used one with 80k miles on it, and 90 day warranty, so how can I lose?

Anyway, no codes after 25 miles, and the lie-o-meter is saying 20.9 mpg, whereas this morning it was reading 12.8 mpg on the same round trip. The pressure being so low was causing the O2 sensors to show lean, which caused the PCM to widen the pulse on the injectors to compensate with more fuel. It would hit the limit on the correction, and throw lean codes. The mpg meter on this truck always ran 19-20, so that's a good indicator that my problem is fixed. I just have to patch the hole under the seat. No sweat. By the way, if you cut the floor to do this, do a clean job and wear mechanic's gloves. The connectors are harder than hell to reach and I cut my hands up pretty bad. I'm sure they'll sting in the morning. Thanks again for all the input, especially 2000LXS for backing up my theory. I found my pump at Jantz Yard 4 in Kenosha, WI. www.yard4.com and they are awesome. Part was pulled and waiting for me when I showed up on lunch today.

 

[2000StreetRod]

Congratulations!

Thanks for posting the solution.

 

[tlestan]

Oh, special thanks to 2000streetrod too, he clued me in that my system had a higher pressure than earlier years. That was the key piece of info right there.

 

[2000LXS]

Glad to hear everyone seems to think intake gaskets all the time. Now we can begin to help people with fuel pump lean banks more seems you get the big drop in gas milage.

 

[ragajungle]

Congrats on solving this!

 

[ThePhoenix]

i am beginning to think I need this...I cannot get above 17 mpg, mostly highway

 

[tlestan]

Hey Phoenix

Low mfg displayed on the mileage computer could be caused by this. Mine had dropped to 16-17 before my codes set. Check the fuel pressure and make sure it's in spec. When's the last time you changed the filter? If you're truck is older than 1998, your pressure regulator is on the rail, and that will cause low pressure if it's leaking or the spring is faililng. My '99 is in the tank, so I think the actual problem was a bad regulator, as the pump never stopped working. I'm going to take the old regulator out of the assembly and use an air compressor and regulator to see where the fuel pressure regulator opens up. I'm betting it's at 33 psi, not 62. It was just easier for me to drop the whole new (used) assembly in the tank than fool around with it. Too cold here to play around. I'll take the old pump into the basement workshop and tinker when I'm bored.

 

[tlestan]

Update

The Mountaineer is still running great 9 months later, and now at 247k miles. No more lean codes. The $50 used fuel pump was a good investment. Trans is starting to slip now and I have the flashing O/D light. More fun under the old pig.