Hey guys
The patient is a 2002 F-150 4.6 extended cab 4x2 Lariat (308,000 Miles). I lost my fuel pump 2 yrs ago had (wiring issues). I had to replace it again about 4 wks ago and again last week. I purchased the OEM wiring diagram and mapped out the wiring as follows....I have checked each leg of wires all the way back to the pump (connector to connector) each section of wire gave consistent results (12.7 volts applied [via power probe], 11.8 volts on meter at other end of wire) ...I know it is a 0.9 volt drop, but because it was the same for each section I checked I figured it must have to do with the wires/connectors I was using to take the measurements? I know low voltage can prematurely kill a fuel pump but is the 0.9v drop enough to do that (if 11.8 is even accurate, I felt during the testing that it was likely 12v but the jumper wires I was using for testing may have been sub-par, or like I stated earlier not the best alligator clip connectors)

I changed the fuel pump, fuel filter and air filter, and after a week I got a PO171 (lean mixture) indicative of a dirty MAF sensor or a weak fuel pump? (I am also hearing some pinging when accelerating up a hill).

I really would like to get this figured out before the 4th pump goes out.

any ideas would be greatly appreciated.

 

I don't even understand what you're doing

What kind of wiring issues did you have? What did you mess up and how?

You just plug the connector in on the fuel pump and it works...... Why are you checking wires?

What indicated to you there was some kind of wiring issue and not a fuel pump issue? Since you apparently can't find one....

Lean mixture can be caused by a lot of things..... Clogged injectors, clogged fuel filter, bad fuel pressure regulator, air leaks after the maf, etc. fuel pumps usually just work and put up pressure, unless the strainer in the tank is clogged up.

What do your fuel trims show.... Does it apply to both Banks or One Bank

 

trying to figure out why I have to keep changing out the fuel pump?

 

So, the initial time the "wiring issue" ended up being an oxidized pin in one of the connectors (I didn't mess anything up, just cleaned the pin and everything was fine until 4 wks ago). I went out to start it and it wouldn't start (no fuel pressure -0 psi...nothing came out of the shrader valve on the fuel rail). changed the pump (not the filter..my bad). and last week was sitting at a light and it died on me, checked the shrader valve on the fuel rail while I was sitting in the intersection (no gauge with me) and got a very weak stream of fuel. tried priming it multiple times before starting to see if could build enough pressure to get out of the intersection, but best it would do is "almost start", had to have it towed home. Put a fuel pressure gauge on it the next day 0 psi. looked up likely causes of premature fuel pump failure 2 primary reasons I found were 1) partial blockage (likely fuel filter..old pump may have thrown shaving/shrapnel into filter when it failed), or 2) reduced voltage to the pump. Figured it was the filter issue since I didn't have the forethought to change it at the same time, so this time (last week) I did the pump and the filter. in the days leading up to the latest pump dying I heard the same pinging, so I deduced that fuel flow actually was probably restricted causing the failure and not a low voltage issue..I checked the voltage through the system 1) because it was an issue on my first failure.2) I wanted to make sure everything was good while I had everything apart so I wouldn't have to either pull the bed off or drop the tank again (I've done it both ways now...both are a pain in the *** to do by yourself). So the lean mixture code I got is not my primary concern...therefore I haven't checked fuel trims. Like you said fuel pumps should just work! except mine keep failing (i have bought each pump from a different store hoping if one brand was notoriously bad or just had frequent failures I would not be buying the same thing. What Im trying to figure out is why these fuel pumps keep dying so I don't have to keep replacing them. the PO171 code appeared for the first time last night (despite hearing pinging [reviously) my concern with the code is when I looked up causes "weak fuel pump" was one of the first issues listed and is consistent with the problems I have been having.

 

[QUOTE=mbb;7816405
Lean mixture can be caused by a lot of things..... Clogged injectors, clogged fuel filter, bad fuel pressure regulator, air leaks after the maf, etc.[/QUOTE]
mine was from the driver's side timing being off just a skotch from a broken guide...just throwing that out there.

 

most common reasons an electric motor will die is excessive heat
1. overworking the pump because your filter or anything downstream is partially clogged.
2. low voltage causing high amperage draw (heat)
3. always running your truck with low fuel. The submersion into the fuel is what cools the pump.

 

Can you post the pumps you've used thus far.. easily ? Any other pressure readings to share. Perhaps before and after a filter change ? What were pressure readings w/regulator disconnected and was it steady under load/during drivecycle.

A new pump should last 90,000 miles on average. Longer if you tend to keep it above 1/2 tank normally.

 

No msg

 

Check the pressure regulator. It may not be a pump problem.