Luvrv8 wrote:
It will not back feed to the starter. Remember a relay uses a low amp power to pull a magnet down to energize a higher amp load. By adding power straight to the fuel pump power will not jump to the pull down side of a relay that in this case is on the start circuit.
Think of it this way, on a starter like ours the battery is connected to the starter at all times, if your theory is correct then power would back feed to the starter switch, the starter switch only energizes the starter solenoid and never cross feeds to the main battery cable. It only pulls a magnet to contact the main battery power to the starter motor windings.
Take another look at the wiring diagram, (the 79/80 diagram is the same cirtuit but much easier to read). With the fuel pump relay in the "relaxed" position the starter solenoid and fuel pump power is connected together. This is so the fuel pump will run in the "start" position of the ignition switch. So--no mater where the power is applied they both are energized.
After the engine starts the alternator charging pulls the fuel pump relay contacts open, disconnecting from the starter circuit and connecting to the alternator/voltage regulator circuit.
Kind of a complicated circuit I know, but that is how it works. Luv fuel pump circuit 101.