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Old 12-02-2019, 11:52 AM   #1
skyphix
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Join Date: Sep 2018
Location: Hampden, ME
Posts: 406
PSI Harness Hookup (How I did mine)

Hey everyone,
I pieced together a few different things I found to hook up my PSI Harness but it took a bit of trial and error. I thought I'd post how I did mine here and provide a place for anyone to ask questions that I might be able to answer. I'll update the thread with photos tonight.

Bulkhead image borrowed from several places floating around the internet, modified for my uses.

1) I moved my battery to the drivers side and used the donor battery cables. I routed the positive battery cable the same as the donor - mounted the junction block to the side of the accessory drive, routing the positive battery cable under the accessory drive tight against the block, under the exhaust manifold, to the starter. The ground I connected directly to the side of the block where the accessory drive bolts on the side (not the face of the block.) My donors negative battery cable had an extra wire coming out of it, so I grounded that to the drivers side fender.

2) I ran the two power wires from the PSI engine-side harness (red wires, big ring terminals) to the same stud on the starter that the positive battery cable connects to. This provides a little tricky because they end up tight to the exhaust manifold - though not touching, it made me a bit nervous, so I tucked them inside the heat shield that snaps over the starter and wrapped the remainder in heat reflective tape good to 2000 degree non-contact and 500 degree contact.

3) I ran the pink wire (second down from the top on the left side of the bulkhead connector) to the "Ignition Signal" wire on the PSI Fuse block. I also used this to trigger the fuel pump relay.

4) I grounded the passenger side of the block (I used the AC mounting holes - any unused threaded hole in the block that is away from the exhaust will work) to the passenger side of the frame using a Grounding strap. I picked up my grounding strap in the Help section of the local parts store.

5) There is a ground with a ring terminal in the engine side of the PSI harness - I grounded this to the rear of the drivers side head.

6) I ran my harness through a 2" hole I drilled just to the rear of the intake on the drivers side. I had a couple of square holes here, and I just drilled the 2" hole around one of them. This put the harness entering the cab behind the heater controls. This worked great for me, but I have a non-AC Dash... so you may need to adjust yours if you have AC.

7) Fuel tank wiring: This was actually pretty easy - I used the same pink wire I used for ignition signaling to signal the fuel pump relay. A simple T-Splice and adding the PSI supplied terminal, then plugging into the relay per their instructions. I then added a 15A inline fuse to the "power feed" wire that I connected to the terminal on the relay, again, per PSI instructions. I used a 12G wire for this - probably overkill but I don't like fires. I picked up some 2 pin weatherpak connectors (I bought mine with pigtails from Del-City - expensive but cheaper than the Weatherpak tool) to connect to the 1987 Fuel pump sender. Grey is power, Purple is level signal. You should already have a wire going to your original sender if you don't have a factory EFI tank. I used that single wire and hooked it to the purple side of the weatherpak connector, and my new fused power wire to the grey side.

8) For the ground on the in-cab portion of the PSI harness (black ring terminal) I just used a self tapping screw through the firewall. Probably not ideal but it works.

9) I currently have my wiring harness and PCM mounted up behind my dash... pretty much with just zip ties. Its not perfect, but its secure and keeps everything out of the way and hidden. I wanted to maintain my glove box so I didnt want to put it there. Again, having a low option, no AC dash really helps with behind dash space.



That's everything I can think of right now... I'll post more photos tonight.
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1980 C10 SWB
2003 Chevy Suburban 2500 LT
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