E21 323i fuel pump relay

[David Mc]

Has anyone ever studied one of these things? They are not just a simple 4 pin relay and mine has a small printed circuit board with what appears to be a timer circuit (contains a 555 IC chip). Do the aftermarker fuel pump relays also contain this circuit, or are they simple 4 pin relays? The only reason I ask is that I was considering replacing the dodgy electro-mechanical relay with a state of the art solid state job for the ultimate in reliability, but even with a circuit diagram am having difficulty in identifying the pin outs.

[nas80]

Id be guessing.I think they fit some sort of timer circuit in so it don't run the pump constant when the ignition is on but engine not running.