2005 Ford 500



January, 22, 2011 AT 4:52 PM

Do you have any suggestions to help figure out why 2005 F150 with 4.2L 6 cyl 2WD will not start. Had this problem approx 1 yr ago. Replaced crank sensor. Still would not run. Found Fuel Pump Control Module on frame was corroded and cracked. Replaced module problem solved. Now truck won't start again. Fuel pump not running. Dropped tank. Applied direct power to fuel pump and it will run. Checked all fuses and relay. Replaced module again. Fuel pump still will not run. Replaced fuel pump. New pump won't run. Can apply power to pump and it will run.


2 Answers


Clothes Horse

January, 29, 2012 AT 11:47 AM

I once had an associate back in my Navy days who could not start his van, we took most of his ignition system apart and could find no open wires or blown fuses that could account for his van not turning over, we sort of gave up looking and put everything back together, somehow once we put all the wires back, the van started up!

We all attributed this to a Naval acronym PFM, (pure FKIN magic).

From what you listed, it sounds like the simplest answer is that following the corroded control module trail, it seems likely that I'd try to find out at what point does the battery voltage get cut off from reaching the fuel pump terminals?

A corroded wire seems like an obvious source for this problem, if you can isolate the wires that supply power to the fuel pump or the control module, I'd check to see if corroded wires are open or have enough resistance due to the corrosion that the corrosion itself is dropping most of the voltage or the current required to operate the fuel pump or the control module itself.

Something I was taught in the Navy a long time ago, check the simplest items first, like the wires that connect the fuel pump or control module, we were always told to check the fuses first, then check for anything in the wiring or circuitry that could mimic a blown fuse or open wire or an increase in resistance which would drop the voltage necessary for normal operation significantly.

I'm still trying to isolate why my 2003 F-150 4.2L manual truck operated normally 3 months ago before I last disconnected the battery and now suddenly, the fuel isn't being delivered to the engine, until I check all the normal suspects, I'm lost for explaining why I didn't receive a hint that something like this was going to happen, I'd like to think that this is just a clogged fuel filter that I can easily replace if that's the source of my problem.



January, 29, 2012 AT 1:21 PM

To the original poster.
You have a module controlled, variable pressure fuel pump circuit. It uses a pressure sensor in the fuel rail and a pressure sensor in the fuel tank to make it's decisions and you really need a professional scan tool to command the FPDM while using a mechanical fuel pressure gauge to measure the response. He FPDM is the most common failure.

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