Are PD fuel pumps - polar sensitive ?

[Classic Mini]

Tried unsuccessfully to convert my Mini 850 from positive earth to negative earth. Changed battery terminals round, coil leads round and also "shorted" the dynamo big & little terminals. Engine spins but will not fire up. Reverted to positive earth and it all works properly. Looked at fuel pump tonight - I am 99% sure its a PD type as it has 2 spade terminals.....Is it just a case of swapping these round as well ? Any assistance much appreciated

[DanGT]

Yes the pump has to be the right way. Its got to be a DC motor so if the wrong way round the motor will go backwoods.