Fuel pump relay buzzing

[Cyrix2k]

I'm trying to diagnose my '91 e30 that has a full '92 M50NV swap. The fuel pump wasn't turning on with the key when I got the car but it turns out the harness adapter had a faulty connection for the fuel pump relay. I fixed that and now the fuel pump relay makes a buzzing sound (it's rapidly turning on and off) - that can't be normal can it? I've tried two ecus (a red label and a blue label) that came with the car, but I have access to a third, known working red label that I can also try after I verify there are no more wiring faults. Anyway, do you guys have any ideas as to what would cause the FP relay to buzz?

P.S. I sincerely doubt this has anything to do with the leak.

[Cyrix2k]

Update: is it supposed to buzz? because the car runs...

[Todd Black 88]

Measure the voltage at the coil of the relay. If its below spec, find the wiring issue causing the voltage drop. If its within spec, replace the relay.