Ok guys the fuel gauge in my 67 only went up to the empty spot when I start the car or put my key to the aux position. so I went out and bought a new sending unit and installed it and still it doesn't work. now here is the weird part. if I take the sending unit out of the tank and push the base of the unit to a solid ground the gauge works and then as soon as I install it, it doesn't work. is this thing supposed to be grounded?