Fuel pump teaser?

[320Touring]

I've had a fuel pump failure on my 1988 320i. Pump has been tested with 12v, did not run.

no problems thinks I, and fitted a spare pump. No Joy,

removed that pump, checked for 12v at the pump feed wires- all good.

test ANOTHER spare pump with a 12v bench power supply-spins up lovely.

fit the other pump to car, no luck-pump not running. fuse ok, rely clicking, 12v at pump end

any ideas folks?

[maxfield]

When checking for 12v I'm assuming you used the same earth as the pump?

[Grrrmachine]

When checking for 12V, did you use a meter or a bulb?

[320Touring]

When checking for 12v I'm assuming you used the same earth as the pump?

Yeah checked at the 2 wires tat connect to the pins on the pump

When checking for 12V, did you use a meter or a bulb?

It was a meter used..

are you both thinking earthing issues?

[Brianmoooore]

A meter is rarely the test instrument of choice when voltage testing around a car. On an unloaded circuit there can be a series resistance (bad contact, corroded joint, etc.) of several thousand ohms, and the meter will still read as if the line is in perfect order.
Always use a simple 12 volt bulb of at least a few watts for testing this kind of thing. I've posted this once or twice before!