fuel pump kill swith

 NSGrimace,

 If he wires it that way, he will be ENERGIZING the coil of the relay to kill his fuel pump. I know a relay coil only draws 100-200 milliamps, but that is easily enough to flatten a battery in a few days. If he drove it every day he might be alright, but if he left it parked for a couple days, especially if it was cold outside, he would have a dead battery for sure. 50 milliamps is the absolute maximum IMHO for a key off current draw and most modern vehicles already draw 20-30 milliamps with thier onboard computers.

 rugerm44,

 You can use NSGrimace's instructions, but interrupt your fuel pump wire with terminals 87 and 30. That way you you will have to turn the toggle switch on to make the fuel pump run, and when you turn it off to kill the pump when your truck is parked, it wont be drawing any current from your battery. Use a good quality (Bosch or Hella) relay not one of those no-name ones you get at walmart. If the relay ever does go bad and won't turn on (pretty unlikely) just unplug it and put a jumper wire between the wires that were connected to 87 and 30 on the relay. You can make up a little 2 or 3 inch jumper wire with a male spade terminal on each end and keep it hidden in your glove box if you want.

 Another (probably better) way to do what you want to do is to simply interrupt the wire going to the coil of the factory fuel pump relay on your truck with a toggle switch. That way, you only have 1 fuel pump relay, not 2 and you don't have to buy a relay, just a switch.  

Sorry NSGrimmace, i didn't realize until just now that you meant to connect terminal 86 of the relay to switched power, not constant 12v. You are right, your method would work fine and also be more failsafe than using 87 and 30. 

I do still think that it would be better to not use a relay at all and interrupt the wire going to pin 85 or 86 (whichever is the ground wire) of the factory fuel pump relay with a hidden toggle switch.