mine are generally within about .3 volts of each other.... with the fuel pump voltage almost always being higher. there are exceptions, like when a large electrical draw is kicked on (fans, lots of brake lights(8 on a 88-96 grand prix), A/C etc). then all bets are off, since battery voltage will always dip, yet fuel pump voltage may stay close to where it's at, sometimes it will also drop. may depend on which load causes it.