[Refugee]

Testing without a meter.
First buzz test all the pickup wires and establish the inputs to the amplifier and the ground wires With no wires on the pickup.
Put one input wire on one pickup terminal and buzz test all the others on the pickup making a note of the loudness of the buzz. Repeat for each pin.
You should find two pins that buzz louder in both directions. These are the ground pins and should be connected to the ground wires to the amplifier and the other two to the amplifier inputs.
If you scan the pickup with a magnifying glass you might find some markings.
I suspect that there is a link inside the pickup between the two ground pins just lurking there to confuse you. The pin-outs are often not logical on pickups.