I finally located a domestic source for one of the Pierburg fuel pumps mentioned above, and got one. Ninety bucks (shipping included)
from here:
https://www.rmeuropean.com/Products/113 ... FG244.aspx. It was sent out immediately from their wholesale supplier
in Georgia. Here it is installed in my mechanical fuel pump test rig (note that the fuel hose connections would normally be pointing in
the opposite direction):
It's pretty clear that this is the same pump made by the Italian firm BCD-Corona, and being sold here:
https://www.paruzzi.com/uk/volkswagen/e ... lines/4541
Those folks also sell a nice rebuild kit for the same pump, as item #4542.
The Pierburg pump I got has had all 3 of the BCD logos that were cast into the pump body ground off, and they did a nice job of it.
The first thing I did was take it all apart:
I didn't take out the internal operating lever because doing so would have disturbed the staking holding the lever
shaft in place. The pump is cleverly designed so that the entire diaphragm assembly can be removed after turning it
90 degrees. The diaphragm has a little tab on it so you can tell if its orientation is correct.
I then put it back together, preloading the diaphragm 5.5 mm (since it's an "alternator-style" pump), and did an output pressure test.
I initially had some difficulty getting a stable ouput pressure from the pump. At one point, I could get it up to 10.5 psi, but something
was clearly wrong, as all previous pumps I had tested smoothly pumped up to their max, and stayed there no matter how energetically
I operated the pump mechanism. My theory is that I didn't preload the diaphragm quite enough, and it was being stretched by the
inertia of the operating rod and thereby adding to the pressure provided by the diaphragm spring. At any rate, I added six gaskets under
the pump, the stack measuring 2 mm with caliper, but probably a little less after bolting the pump back in place. I was then able to
get a stable, smooth output pressure of about 4.5-4.3 psi.
This seems like a fairly well-made pump. The diaphragm is of real Effbe material, nice and thick. The input hose connection (top, black
plastic) is marked as such. The output connection is brass. The screws joining top and bottom are M4, rather than the usual M5. It was
leak-free with only moderate torque applied to the fasteners. I did notice a little ridge (pointed to by red arrow in one of the photos above)
on the operating lever that was causing a noise, and notchy movement, when the operating rod slid over it. I ground it down with
a carbide file burr in my Dremel tool, and all was fine. Although the mode of operation is identical with the old original VW/Pierburg
pumps, it seems that none of the parts are interchangeable.