Fuel pump question...

I have a 72 and a few years back I installed an edelbrock electric fuel pump. I just installed a Dakota Digital dash this week and now when I start the car, everything seems fine but when I turn on the directionals I can hear the pump make a surging sound as the lights flash. It almost seems like a ground issue but I'm not sure were to look. I never did install a relay in the power line as I didn't know if I really needed one for that pump. It's a mildly built 350. any ideas would be greatly appreciated. Thanks.