Hi, new to this forum. My truck is 1987 GMC Sierra R3500, with 7.4L and TBI, duel fuel tanks. Just got it restored, but I can’t select fuel from both tanks, I don’t hear any clicking sound in the fuel selector valve, nor the sending units. Only when I turn the key to on, I can hear the driver side fuel pump. I checked the electric on the selector switch (no power), checked the electric to the fuel valve selector no power, so are the fuel sending units. I’ll be replace both sending units with new ones, But why no electric power? Any thoughts?