I'm trying to resolve what I believe is a fuel pressure problem with
my '88 240. The car will barely idle and has no power. I replaced the
in-tank pump (was definitely bad) and the fuel filter. Main fuel pump
is working, and passes the volume test (1L @ 30 seconds).

When I pinch off the return line from the pressure regulator, car runs
fine. This suggested to me that the regulator was a dud (not holding
pressure). I replaced the regulator - problem still there, but
everything is still fine with the return line pinched off.

I checked the current draw on my main pump. 3.5 Amps without the
return line pinched, 8 Amps with the return line pinched.

Any ideas... perhaps my replacement regulator was a dud too? I was certain that the regulator had to be bad with the engine responding to artificially increasing the pressure with the return line pinched.

Thanks,
Andrew