I have been fighting with my fuel pumps all summer. So I feel for you and I'm wondering what to do.
1996 Volvo Penta FI. (Ford 302)
Initially, my high pressure pump quit. I replaced it, and it ran well for about a week.
Then the Low pressure pump was not pumping enough, so I replaced it and it ran well for another week.
That low pressure pump broke. I replaced it, and it ran well for a month, but then my High pressure pump started screaming. (motor still runs fine)
Check the fuel pressure on the resevoir tank while high pressure pump is screaming. I have no pressure. (I figure thats my problem)
Just completely reconfigured the low pressure pump. (after 2 have broke, I'm going a different route)
I put a Holley Marine 6psi pump in with a seperate fuel filter and ran it straight to the Fuel Resevior tank.
I now have 4 psi on the reservoir tank itself. (2-4psi is where it should be)
My high pressure pump is still screaming at idle and at speed.
Pulled the return line off between the Pressure regulator and the resevior tank. Cranked it up, and that line was pouring fuel. I was told if that happend, the pressure regulator was working properly and not clogged. (I have no idea if that is the correct way to check a regulator)
Currently. Motor runs fine. 34psi on the fuel rail which is where its suppose to be.
4 psi on the resevoir tank, also where its suppose to be.
And a high pressure pump thats screaming like no tomorrow.
I'm about to rip all of it out and put a carberator on there.
Then I can complain about not being able to tune that.
any ideas on mine? and how do you check a pressure regulator?