Good luck Steve! I seem to remember something in the past about someone having a faulty tacho causing all sorts of problems where the tach wire was shorted in the tacho its self. This could also mean that there would be no flyback pulse to liven up the speed sensing module and hence fuel pump relay. You can check for this by doing a resistance check between the green wire on the output of the radio suppressor and ground. If its over say 1000 ohms you should be able to eliminate that as a problem... if its under 200 ohms I would be a bit suspicious of anything connected to the tach wire.