Hi gents, I have a 94 f150 4.9L 5spd dual tank. tank #2 was giving me trouble so I replaced the fuel pump. At first it was running great with the new pump then after three weeks it began bogging out like the fuel pump wasn't pumping properly. My mechanic pulled it out and replaced it with another new one. After that ,the truck was running great and then, I made a U-turn on a street and the truck began with the same symptoms again, it began bogging out. I don't think it could be another faulty new fuel pump. I need someones help. Hopefully someone has Gond through this and can help me. I really don't want to put in another new pump. Could it be an electrical issue? If so where do I start in finding where the problem is? Please hit me up if you know anything that I can do.
Thanks guys,
Raul

 

Which tank is "#2" front or rear? So just to clarify, it does only bog down when you are using thank #2? And is the truck having issues starting up? And is it having more trouble at higher or lower rpms? And you should check the fuel pressure.
I am more familiar with the 87-89 fuel system, but we will all try to help the best we can, the more info we get, the better.

 

Tank #2 is the rear tank and it starts up fine and works fine at the beginning and then when it wants to it just starts to sputter and I have to immediately switch to Tank #1 which works fine. When it acts up it starts to sputter and even if I floor it its like its not pumping the gas to the engine. It is really annoying because it is the second pump I put that is doing the same thing. I know it acts up when ai make a sharp turn or like I stated before, it began after making a U turn.

 

That sounds to me like it is not an electrical issue. Maybe there is a clog in the line restricting fuel flow, or if there is a lot of dirt in the tank, the fuel pump strainer could be clogging up too. These are just guesses. So Id say the next step would be to check fuel pressure.

 

Yes, that's very likely. What's the brand, PN, & source of the replacement pump(s)? Was any of them TESTED before replacement?Start by learning how the system is supposed to work. Then find out IF it's working that way. Click this & read all the captions:


(phone app link)

You blindly guessed that the root of the symptom was in the fuel system, and there are more systems that can cause it, so you probably guessed wrong. The most-likely cause of almost every symptom on these old trucks is BATTERY TERMINALS, because everything electrical & electronic relies on them. Compare yours to what this album describes:


(phone app link)