73-87 Chevy _ GMC Trucks > LT/LS Swaps

swapping 6.2 LS3 into 1987 that had TBI. The wires I dont need for engine?

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mmanship:
The 1987 TBI had a computer and many wires.  I have installed a PSI engine harness and had the ECM programed.  The old computer is out.  Has anyone done the LS conversion into a 87 that had the TBI?   270-779-3007  Mike

frotosride:
Any progress on this. If you haven't figured this out I will surely help you out with the odd and ends.

frotosride:
Depending on what all you end up keeping there can be a lot deleted. The first Pic is the whole harness unplugged and pulled out of the fire wall. Next (2 pics) is the bulkhead connector for your fuse box. Oriented the way that you see here (the top row left to right=orange, tan/white, dark grey, red{large gauge}), the orange wire is the 12vdc (+) to the relay positive, then an empty spot, and the tan white one is power to the pump from the relay and the oil pressure switch. If you desire to keep the original relay for the fuel pump then leave these two wires and use the green wire coming from the relay to the ECM as your switching power from the LS PCM. the major difference is that the trucks configuration only uses the relay to initially prime the pump. after that the switch supplies power to the fuel pump. This was a safety feature that isn't used in this manor anymore. I'm not sure if the OEM ralay can handle continuous running but it's worth a shot. Other than that the large gage pink wire is the OE coil primary 12vdc(+). you can use this to supply power to your aftermarket harness as it is Pink in color which means ignition 1 (2,3) key on power only.


Complete TBI harness unplugged from the ECM and pulled through the firewall.




The top row left to right=orange, tan/white, dark grey, red{large gauge}



I removed that whole row because I do not intend on keeping any of it, but here is what they look like.
There really isn't anything else to keep from the OEM TBI harness if you have an aftermarket harness. Simply hook up your switching power supply from the  (10ga pink wire) and all time hot to the Bulkhead splitter to the left of the brake booster and grounds. remember to ground the engine to the frame and frame to battery. Good tip... always try and run a ground from the alternator to the frame-battery ground bolt. The OEM Vehicle Speed Sensor (VSS) is mounted to the speedo, behing the gauge cluster. I do not remember the exact pulse rate of this one but I know there was doubt that it woul;d put out an acceptable signwave for the modern computer. A pass through adapter is the best option unless you are going all out and putting new gauges in right away. Personally I cannot afford the gauges I want right now so OEM it is for me...for a while.

frotosride:
Since I found out my pics are not loading properly (google's super secret special coding sauce) I made an album specific for the TBI harness. I will try and label the pics you you have a better Idea of what is what so you can decide to just start from scratch or cut and splice.

https://photos.app.goo.gl/c33hqCrmopzesk388

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