87 Burb 4.8 swap

[nobox351y]

Got the 4.8 fired up today. Couple of small wiring issues to sort out. I followed lt1swap.com fairly closely to rework the harness and make it a standalone unit.

When I got the truck to start the first time, it ran good, but when I tried to shut the motor off it just kept running.
I have 2 pink wires which are listed as PCM Ignition Supply on the pin out list on lt1swap. One of these wires has 12 volts when the pcm gets 12 volts.

I cut those 2 wires out of the fuseblock and the motor still starts and runs fine. Im going to look at the pinout again and try to get it figured out.

Any thoughts on how a pink wire from the pcm has 12 volts. All the other pink wires are switched 12 volts.


Next issue: Cam sensor is throwing a code and it is causing a long crank on start up. Going to check 5 volt reference and ground in the morning. Best place to look before buying a new sensor?

[Matt Cramer]

Are there any relay coils that need to be fed switched 12V being fed constant 12V by mistake? Sometimes these can backfeed.

[nobox351y]

Originally Posted by Matt Cramer

Are there any relay coils that need to be fed switched 12V being fed constant 12V by mistake? Sometimes these can backfeed.

The fuseblock/relay I installed was being back fed. How a pink wire out of the pcm has 12 volts, I don't understand. Every other pink wire in the harness needs switched 12 volts.

Haven't had time yet today to sort it out.
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[nobox351y]

When I was taking the harness apart I pulled pins 19 and 20 out of the blue connector. PCM Battery Supply and PCM ignition supply. I swapped them in the connector when I put it back together. Got it corrected. No more back feeding.