Starter Wiring Help

[Jferrante]

I have a 6.0 with a PSI harness and am having trouble wiring this up correctly.
I have the main hot from the battery on the main post, the 2 black wires on the same post (per PSI instructions) then I have the Red wire that comes from the drivers side fuse block - this is where I am having an issue. If I put the red wire to the main post it doesn't turn over, if I put it on the small post of the starter I get it to run the starter but even when the key is off.

My troubleshooting is either the wiring at the relays is wrong or I am missing something altogether at the starter. I should only have starter full circuit with the key in the on position....
Any help is appreciated.

[Wildkarde]

I've never actually seen a PSI harness in person, but looking at the pictures in the instructions and reading them, the red wire coming out of the fuse block should go to a "ignition" source. The two black ones with the ring terminals go to either the large post on the starter or the battery "+" directly. On an ignition switch there are basically 3 different outputs. Accessory, which has power when the switch is in ACC and On, but not when cranking. Ignition, which has power when On, and when cranking. And Start which only has power in the cranking position.

You need to find a wire that has power when the key is on and while the engine is cranking. I like to use the one that powered the Ignition coil since it will already be in the engine compartment. Also, there is no actual cranking wire in that harness, you will need to either use the one that was already on the truck or run a new one yourself.

[davepl]

In my case starting the car was completely outside the scope of the LS harness.

There are two wires that go to your starter:

1) The big starter cable that runs to the battery post
2) The smaller purple wire that runs from the solenoid to ignition switch (and through the neutral safety)

You want the purple wire from the key to the solenoid. When you turn the key, the purple wire will go live and energize the solenoid. That in turn kicks the starter into action, drawing from that main starter cable.

Now it's up to your LS harness and computer to recognize that the engine is on and turning and to start firing the injectors and coils. For that it needs power and so on, which it gets directly from the battery. There is also an Ignition sense line (typically pink) that the ECM has that tells it when the ACC/IGN is ON.

What system is this?

[truckdude239]

The red goes to the big post and then u need to find the facotry signal wire from the igntion switch there is no signal wire in the ls harness

[Jferrante]

Thanks - the truck was running before I tore it down to the frame so I was working off what was there and I am missing something obviously. I just tested a direct line from the small post to the ignition switch and that gets it to turn but now I need to figure out where that wire needs to go on the other side of the relay to make it all work.

[Wildkarde]

is this the harness you have https://www.psiconversion.com/instru...structions.pdf

If so, what I said in my earlier post is correct. That small red wire energizes one of those realays, which then powers all stuff on the engine that needs switched 12V, coils, injectors, O2 heaters, ECM, TAC module and a few other things. The two large black wires that are down by the crank sensor go to the large battery post.

If you still have it, the coil/distributor wire works well for triggering the switched 12V relay.

[mongocanfly]

I used a psi harness...the psi doesn't do the actual starter cranking ...you need to use original truck starter wiring that cranked your old engine....

[Jferrante]

Originally Posted by mongocanfly

I used a psi harness...the psi doesn't do the actual starter cranking ...you need to use original truck starter wiring that cranked your old engine....

This is where I was missing - I ran a wire from the starter to the ignition on the truck harness and all is good now. Now i need to figure out why my fuel pump wire from the PSI harness isn't sending a signal in ACC mode.

[mongocanfly]

acc or switch on?
my pump doesn't run in acc.....only switch on...really no need for it in acc

[Wildkarde]

The fuel pump should be controlled by the computer, will run for ~3s when you first turn the ignition on unless the computer detects the engine spinning.

[binford]

Correct, when you turn the key to ON the fuel pump runs for a few seconds. When you turn the key to Start, the starter will spin and the PCM will be pulsing the fuel injectors. So the fuel pump is on, but you can't hear it over the engine.