Well something that's long been on my mind is the electric fuel pump to feed the MFI system, and specifically the MFI fuel filter console. At first glance the fuel system feeding the MFI pump seems overly complex:
This post focuses on the thicker lines in the picture above. Even the arrangement at the fuel tank seems overly complex at first, but it's not quite as bad as it seems. The original style fuel pump had a third nipple (I'll come up with a limerick about this later) that was a return path for the internal pressure regulator. So that can be ignored, or, indeed, replaced with a "regular" pump.
Now a bit of a disclaimer, this is all very temporary, and will be improved upon later... I just wanted proof of concept before I made any more commitment to part locations and cutting actual fuel lines, etc:
My "normal" fuel pump feeding the MFI pump on my test rig (see above disclaimer!)
It's a run of the mill Bosch pump for a 84-89 3.2 Carrera. I chose it because it is readily available, inexpensive, and has a plain hose attachment on the suction end that matches the diameter of the tank filter screen outlet on the early style tank. Although it will produce much more pressure than called on in this application, it doesn't have to.
I was pretty elated when I hooked everything up in the factory configuration and the pressure at the MFI pump head was 12 psi or so. I tested the pressure at each point in the system and there were no surprises (see dry break test fitting on the banjo inlet of the filter console):
I initially used clear plastic tubing so I could see if I was getting any cavitation or air bubbles, etc. - I added some red colored fuel injection cleaner to my test fluid so that's why the hoses look pink:
The test fluid is more or less non-flammable, and somewhat low odor - it smells suspiciously like mineral spirits.
So that's that. But it still doesn't explain the fuel filter console and why it's so complicated. Why does the fuel go in, and out, to the MFI pump and back, then through it a second time? Turns out the passages in the console are connected somewhat. I always assumed this had to do with supplying high pressure, fresh, fuel to the cold start solenoid:
