Please help! Severe bucking, erratic fuel pressure

[ford141]

I just posted this over at F150online, but I figured I'd post here to see if any of you have experienced the same issue, hopefully someone has some suggestions for the problem that I just started having with my truck. First the current stats: 05 FX4, 5.4, K&N FIPK, Edge tuner on Transmission only tune, Magnaflow exhaust, 4.56 gears, 35" tires.

Within the last few days I have been experiencing an intermittent hesitation and bucking problem that comes on suddenly. When this happens, the truck feels like you are holding the throttle wide open, and turning the ignition on and off in 2-3 sec intervals. Shutting the truck off and immediately restarting it does not clear the problem, but if it sits for a while it might not do it for another day or two. I set the Edge to display the fuel rail pressure, and while it is bucking the fuel pressure is everywhere, dropping to zero, then up to 70, then leveling out to 30, then repeat the cycle. When it is running fine, fuel pressure is maintained between 38-41psi all the time.

The bad thing is that it is not throwing a check engine light. It just acts like it is running out of fuel in 2-3 sec intervals. At first I suspected fuel line freezeup (it has been -5 here in PA for a few day), so I put a bottle of HEET in the tank during fillup, but it didn't help. I then replaced the fuel filter with a Motorcraft replacement, but still no luck. Could the fuel pump be going? I've had fuel pumps go out, but usually when they quit, they are done, not this random intermittent crap.

The really weird thing is that about 3 weeks ago, I got a random check engine light when I started the truck up. It started fine, but I pulled the codes anyway. It had 3 codes: fuel rail pressure sensor failure, fuel pump driver failure, and fuel pump failure. It ran perfectly at the time, so I cleared the codes and they have not came back again. Now that I am having a problem, NO CODES...

I'm at a loss right now as to what the problem is. If I trust what the codes say from 3 weeks ago, I'd have to replace the entire fuel system. That seems illogical that everything can go bad at one time. Any suggestions on how I should go about narrowing down this problem?

Btw, truck is out of warranty.

 

[blacksnapon]

what happens when you remove the edge?

 

[ford141]

I have not tried removing the Edge, since I have been using it to monitor fuel pressure, plus I'm using it to calibrate my speedo for the 35" tires and 4.56 gears. It is not modifying the engine calibrations at all, only the speedo calibration and the tranny shift points. Not saying that it isn't the problem, but it has been on there for 3 years without any issues.

Here's what I found out last night:

I tried to drive home last night but it was bucking and stalling again, so I called my buddy with his '95 F350 Crew to get my trailer and come and pick me up. While I was waiting for him, I ran a diagnostic with the Edge and it came up with a code saying that the fuel pump driver module was offline. I did some searching through F150online and found a few threads where people have had the driver module bases rust out, allowing water to get into the module and short the circuitry, which then causes the fuel pump to run out of control, causing erratic fuel pressure fluctuations. I'm going to drop the spare tonight to see if I can locate the module, hopefully that is the only problem.

Has anyone heard of this problem?

 

[Truckin4life]

personally no, but it might be worth it to take a look at it.

Take it apart so you can see the bottom if its fine, then its likely not your problem....

 

[ford141]

The problem is now fixed. I bought a new fuel pump driver module and installed it this afternoon. The module is 2 piece, with a cast aluminum base and a sealed plastic cover. The factory mounts this module on a partially-flattened area on the tubular crossmember directly about the spare tire. The problem is that the mounting position allows water, dirt, and road salt to settle between the module and the crossmember, which corrodes the aluminum base. This corrosion, along with freezing of trapped water lifts up the module from the crossmember until it cracks the module in half and cracks the plastic cover on the top. Once the cover is cracked, water can get inside the electronics and kill the module.

Just a tech tip to anyone who drives in cold weather, especially where they use a lot of road salt, it would be worth your while to drop the spare, unbolt the module, and clean the backside of it before coating it with something to keep it protected. I sprayed the back of the new module and the crossmember with rubberized undercoating, then installed the module with the undercoating still wet to "seal" off the area so that water and dirt can't get between the mounting surface. This 10-15 minutes of preventative maintenance could save you from buying an $80 FPDM.

 

[slmann]

Glad to hear you got it fixed and thanks for the tip.

 

[TexasRho83]

The problem is now fixed. I bought a new fuel pump driver module and installed it this afternoon. The module is 2 piece, with a cast aluminum base and a sealed plastic cover. The factory mounts this module on a partially-flattened area on the tubular crossmember directly about the spare tire. The problem is that the mounting position allows water, dirt, and road salt to settle between the module and the crossmember, which corrodes the aluminum base. This corrosion, along with freezing of trapped water lifts up the module from the crossmember until it cracks the module in half and cracks the plastic cover on the top. Once the cover is cracked, water can get inside the electronics and kill the module.

Just a tech tip to anyone who drives in cold weather, especially where they use a lot of road salt, it would be worth your while to drop the spare, unbolt the module, and clean the backside of it before coating it with something to keep it protected. I sprayed the back of the new module and the crossmember with rubberized undercoating, then installed the module with the undercoating still wet to "seal" off the area so that water and dirt can't get between the mounting surface. This 10-15 minutes of preventative maintenance could save you from buying an $80 FPDM.

VERY GOOD INFO

 

[Boomer556]

I think the real problem is dissimilar metal corrosion between the steel frame and aluminum back of the module. Throw in some salt and the clock starts ticking. Borman salves this with rubber spacers to install between the unit and the frame cross-member.

 

[78F250SCCS]

Good tech info. I have a 05 and I do live in the rust belt. That is something I'll have to check.