Wiring

I have checked the inertia switch. There seems to be power to the relay and to the coil on the relay but there is some kind of funky switched ground or something.

Yes ECM grounds check fuel pressure can hear pump run? check for spark was check engine light on?

On this model, are you getting power to the engine computer? the relay is controlled by the PCM and once it grounds inside the PCM it delivers power to the inertia switch and ultimately to the fuel pump. You should have voltage only for two seconds when turning the key on or while cranking, checking any other time will give you false readings.