Don asks, "Can you give me any leads?"
Sure. First a scribbled diagram for you to look over. This diagram I scratched out will give you a good idea of what you need, even the "name" of the switch you need.
Dual Fuel SystemBig image but fast loading. Scroll up and down.
Download my drawing then save it somewhere or simply print it.
An "SPDT" switch is simply a toggle switch or rocker switch which has 2 "on" positions. Some will have a middle "off" position. You can hook up 2 devices and turn on one or the other but not both. This is to switch between sending units.
A "DPDT" switch is 2 switches in one like having 2 SPDT switches in one box, single toggle or rocker works two switches inside, at the same time. This is to switch sending units and to switch an electric fuel valve.
An electric fuel valve usually has only one "hot" wire, then your usual ground wire. A device inside slides to one side when power is applied, spring pushes it to the other side when power is turned off. This switches between fuel tanks.
Study my diagram so what follows will make sense to you. Once you have a good mental image of what you need, then you can find parts on your own and save money.
I am splitting up posts to address each topic individually. More to come.
Billyray
