Have a real head scratcher.

Bought a used 2003 FX4. Ran fine, had a few mechanical non drive line problems, but that was known.

Third day I had it the fuel pump died four hours from home in the check point getting on base. Good thing the Army guys are strong, we pushed it to one side and waited for the tow truck. Got it towed and the pump replaced. Now comes the weird part.

Since the pump replacement it stumbles shortly after filling up, and ONLY after filling up.

Replaced the filter. Placing it right above the transfer case cross member was not a smart idea Ford!

No change.

Swapped the gas cap with a retired ranger.

No change.

Just for grins I popped the gas cap for a while as if I was filling it... Again no change. This was done after a recent fill so the tank was nearly full.

Next step is to run it down a bit and pop the cap without actually filling it and see if it reacts.

Thought about checking the pressure, but I don't see a test port. Or I'm looking in the wrong location.

Hooked up my bluetooth ODBII reader, it gives fuel flow, but not fuel pressure so That's out.

There's gotta be somebody smarter than me on this one.

 

You should find two test ports on each fuel rail. That's how it is on the 4 cylinder (only one because one rail) and my 3.0 v6. I'd imagine the 4.0 is similar. Definately an odd problem.

 

Welcome to the forum

Some of the early 2000's 4.0l SOHC engines didn't have fuel pressure test ports

If it was there you would see it, usually passenger side fuel rail toward the back by cylinder #3

If you over fill the tank you can get fuel into Charcoal canister, EVAP system

Usually you will get EVAP codes and CEL(check engine light) will come on

You don't mention any codes.

Could the stumbling be related to the engine off time when filling up, vs adding the gasoline to the tank?

I.E. is there any issue when you stop for 5-10minutes any other time?

Stumbling and bogging down are classic Dirty MAF sensor complaints, easy to clean these and take that off the table.

 

When you fill it up, do you continue to top it off after the pump automatically shuts off? If so this could cause the vapor reservoir to get fuel in it and could find it way into the engine, resulting in the stumble. I had this happen once when I purposely tried to get as much fuel in the tank as possible. It is also possible something is wrong inside the tank that allows fuel to get into the reservoir. I don't have a clue as to what that could be. When you add fuel to it the next time, try not filling it all the way to see if that helps.

 

Found the test port on the back of the passenger rail... pointing to the fire wall. Go figure. I'm picking up a fuel pressure test kit next time I go past Harbor Freight, $20.

Did not think about the canister, but I didn't have any problems prior to the fuel pump going out, and I'm leery of it being connected to that somehow because I didn't do the job. Out of town breakdown.

Anybody know where the canister is located on the 4 x 4 ?

Will give it a try on the next fill up, but on all my vehicles I fill the same way, and they are all Fords, two of them Rangers. Full tilt until it clicks off. Give it a second for the foam to settle then one more time on the lowest notch until it clicks off a second time. Same way I filled prior to the pump going out with no problems.

No codes / check engine light.

 

If I'm not mistaken, it's somewhere around the spare tire carrier. It's rather large and, black of course.

 

Will have to crawl under and take a look. As far as I know they only dropped the tank and driveshaft to change the pump.

Oh and of course they just 'had' to sell me the whole assembly and not just change the actual pump...

 

Had to stop by the dealership for other things today, and the Mechanic agrees it's probably tied to the evap canister system.

Did a little research and some systems use a check valve built into the canister ( horizontal PVC can back by the spare tire ) and some use a check valve built into the connection on the top of the fuel tank.

As this problem appeared with the dropping and reinstalling of the fuel tank I'm leaning toward the latter, but I don't want to go through dropping the tank just to verify the check is in the fitting.

Anybody have access to the manual showing the tank connections or evap system? Or have recently dropped a tank and could advise?

 

Remove or lift the bed, 6 bolts and tail light wiring, and you don't have to drain the tank, plus much much easier to see and work on everything.

Loads of videos on the different moving bed options and tools needed.

Didn't included unhooking filler tube because you have to do that either way.

 

If you have the fiberglass bed, it will be VERY heavy. The non-stepside version however not so much.

 

4-30 Update

Well I think I HAD a problem with the vent fitting on the top of the tank. I reached up tracking the line from the canister just to make sure there wasn't a link or something. Everything seemed fine, wiggled the tube and stuff, no apparent problem. She took it on a road trip with the warning of the chugging after a fill.

And there was no problem!

I got one minor hick up when I filled a few days later, but I only noticed it because I was looking for it. I would guess the plastic housing for the check valve in that top of the tank insert was binding some how and that either the long drive or my wiggle / twist somehow set things right.