Originally Posted by Sportwagon75
Well...I thought I had this elusive little problem solved.
. . .
Does anyone have any other suggestions or insight into this problem?? I've become pretty good at diagnosing 1975 F/I problems but this one has me scratching my head. -SD
PS - The tank is clean. Pickup sock, fuel pump & filters are all new.
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My only question is: You talk about a fuel "sock" ('75 tank and fuel pickup, right?) and that it's new . . . you did this personally or watched someone do it with a new, in the box NOS part, right? So, where did you find an NOS in-tank filter or was your filter merely "cleaned"? I'm NOT trying to be a smart-ass here, just trying to get the facts straight. It makes a BIG difference.
The '75 in-tank "sock" is really more like a very fine meshed metal screen filter than an actual sock over the tank pickup pipe. This IS a replaceable element about 1.9375" dia. x 2.1875" long with a 3/8" hole in the center at one end that slides over the pickup tube, which you already know if you replaced it. Sorry for any repetition here.
I have NOT found a way to reliably "clean" this filter and the mesh is SO fine that if there is the slightest trace of anything in the tank other than gas, the "used, cleaned" filter will clog up again very quickly, at least to the point where it will exhibit the EXACT symptoms you describe.
FI fuel pumps are designed as pressure pumps and their performance and that of the FI system it feeds degrades rapidly if you restrict the input fuel flow in ANY way.
MAYBE one other thing to look at . . . have you checked your return line for flow restrictions? A kink or restriction in your return line and it acts like a pressure regulator by not allowing unimpeded gas flow back to the tank.