Hi Paul,

I'm no expert on this but looking at the wiring diagram the in tank fuel pump runs with the same polarity all the time. I think the main job of this fuel pump is to transfer the fuel over from one side to the other. It is run until the engine starts or when under high load I guess to help supply the low pressure injector pump (in the main injection pump) with the fuel it needs.

Sorry for the confusion, the MTPro is the abbreviated name of the Autodiagnos MultiTester Pro as mentioned on this site quite a lot (good & bad). It is well known for having good Volvo coverage.

Regards

Sean