Hi,
Had a bunch of help on here with my 7.3 IDI. I really appreciate your experience.
I just installed an electric fuel pump past the tank and before the split line from plastic to metal.
ran a line to the cab, but cant find which ignition wire to tap into for key activation and deactivation.,
using a fused line for now to work the pump. plug in fuse, start and run engine,,,, shut off engine,,, pull fuse.
yes its rigged, but I'm new on here... learning a ton about diesels from all you guys.
Thanks for your input...

 

Use a standard "ice cube" relay. Fused line for power to the relay (can get that at the stud on the fender-mounted solenoid). Then trigger the relay from the FSS (fuel shutoff) wire on the injection pump. That's the connector on top that's closer to the front of the truck. The other powers down when the coolant gets warm enough so you don't want that one.

 

That's pretty cool! Thanks! So I'm not sure which wire to connect where, I get power coming in from starter solenoid, and I also get putting a spade connector on the fuel shut off on the IP and connecting a wire to that ,. but not sure where to connect the wire to the electric fuel pump on the relay, should the relay be a 3 prong relay? that would make sense.
the relay probably has a wiring schematic on it. that might answer my question.

 

I think there are other threads showing the wiring, but definitely do your homework so you don't fry anything

Here's a typical base diagram of the relay (yours may not have the pin 87a, just get a four-pin relay).
12 Volt DC 50 Amp Continuous Duty Relay Bosch Relay 0 332 209 138

From hot stud on starter relay/solenoid through a 10 amp fuse to pin 30 of the relay.
Pin 87 of the relay to the fuel pump.
Pin 86 to the FSS wire.
Pin 85 to ground.
And of course the other fuel pump lead to ground

​​​​​​​Hope that helped!

 

DrCharles went over that well.

Just in case the OP is more visually minded, like me, then you can use the diagram on the top of the relay to wire it up.



Basically, that diagram shows two unrelated circuits. The 86-to-85 circuit powers an electromagnet. The 30-87-87a circuit is completely separate from that 86-85 circuit, except for the fact there is a metal switch opening or closing that circuit. That switch is the diagonal line in the diagram.

When you power the 85-86 circuit, the electromagnet engages, and its magnetism moves that metal switch (displayed with the diagonal line) from the 87a position to the 87. When the power is shut off in the 85-86 circuit, the electromagnet disengages, thus turning off its magnetism, and the metal switch returns to its rest position of 87a.

Since the electromagnet is TINY, it draws a negligible current. This means it can be added into an existing stock circuit (like a cigarette lighter or radio circuit) without impacting the load or current of that stock circuit. Since the 30-87 circuit is separate from the 85-86 circuit, you can run higher gauge wire from the battery to your aftermarket accessory, and put a larger current to it without overloading the stock circuit.

Some relays will not have the 87a position. This is called the NC (Normally Closed) position. This allows you to make a circuit that stays closed, until the 85-86 circuit is engaged. The 87 position is called "NO" (Normally Open). That only closes when the 85-86 circuit is powered. For example, I use my NC relay to open circuits like my solar panel charging wires. They should NOT be charging my batteries when the engine is running, so when I turn my key, that powers my NC relay which opens the 87a circuit, thus braking the circuit that allows my solar panels to charge my van batteries.

Most people never use the 87a circuit, because NC situations are rare. Most relays are NO relays, and all you have is the 30-87-86-85 leads. Wire it up as DrCharles explained. HTH