If you've been following the chronicles of Deminimis, you'd know I've been throwing P1211 faults since Baja. Over $1k later, I'm still throwing that same cursed fault. I read of a long time diesel mechanic that was stumped by the same problem. He, like me, tried everything. Eventually, someone suggested looking at the in-tank sending unit as when Ford diesels get around 100k miles on them, the screen in the sending unit can get plugged. I spoke with Powerhouse diesel, explained my situation and Mike also suggested the screen in the sending unit/fuel pickup. However, he was clear to point out it was the screen encased in the plastic housing, not the big screen that you can easily see. Well got after mine today (yesterday was a new fuel pump...more money down the drain) and sure 'nuff, the two filters were 40-50% plugged with rust granules. Yes, rust granules. In fact, there was a fair amount in the bottom of the tank and the retun fuel line was nearly plugged. So cleaned the screens, the whole unit and cleaned out the tank.
Here's the sending unit showing screens after I cracked it open (three snaps):
Well, why stop there. Let's vent this Transfer Flow so I can actually fill it. It had two Ford vents. Those vent have pin holes and vent into a cap. Not very effective. So, first thing is I added a connection to the filler tube for my new vent tube. Not a pretty weld, but a weld it is (old valve cover vent from on my of VW buggy engines -Welded it up and then drilled through the filler tube wall.)
I took the Ford vents apart (they come out of the tank with just a 1/4 turn AND you can get to them without removing the tank -the are a roll over valve). So, took them apart and opened up the hole. Did not reinstall the roll over valve parts as venting into the filler tube. Here are the Ford vents.
Well, how does it all work you ask? Dunno. I only have two hoses left to hook back up, but the heat was too much for me after being out in the sun for nine hours (I did other things today too). So will hook the filler hose and the orig vent hose, fill it back up and hope for the best in the AM, when its cool. So, if your Ford diesel is getting near the six-figure mark, time to clean out that sending unit. If I had it to do over again, I would have just replaced the unit.
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