Within the time I own the E28 I’d never replaced the fuel pump. I replaced the filter back in 2015 but I trusted the pump though. Until the last day of my Wales roadtrip!
After some research I found out the fuel pressure regulator delivers 3.5 BAR at the injectors and my original 520i fuel pump only supplied 3 BAR. So that’s no good! I found a decent 4 BAR fuel pump on ebay: the Johns KSP5014002.
After some hours of trying to loosen the 30 year old clamps: