19sixty5

I have a 67 Cutlass with an LY6/4LE85. The car was running fine last Saturday, parked and did not start Monday afternoon. It will crank, but the fuel pumps, cooling fan, and gauges do not power up. I have switched out relays on the ECM fuse panels also to no avail. The ignition switch passes 12 volts as the accessories (turn signals, wiper, radio, etc are functional. I also used my scan tool and it cannot communicate with the vehicle, it says.
I am not super comfortable poking around, but have removed and re-seated all connectors, etc. I also did not build the car, the previous owner seemed to think the relays were possibly bad.
Any idea of where to start? Could the ECM just die?

Thanks!!!

Professur

You better believe it. That's why so many of us choose to stay old school

oldcutlass

John unfortunately you need to find someone familiar with that setup to help you troubleshoot it. You might do a search to find someone on here that has done a swap like yours or perhaps visit one of the LS boards. Most of us old timers wouldn't know where to start.

z11375ss

Your car has rejected the transplant! Just kidding. I hope you find your problem. I nearly did one of these for my buddy. We went with a 502 chevy instead.

MDchanic

+1.

You've angered the gods.

You need to find a "tuner" of riceburners to massage its electrons.

I can help you figure out how to install a carburetor and points ignition on it, though.

- Eric

garys 68&72

Your gauges are not powered through the ecu, unless the dash from the LY6 was swapped over. You have a voltage feed problem between the ignition and ecu. Could be as simple as your ignition switch. With the key in run start checking for 12V. If the harness is original, all the pink wires should be hot.
Another thing to be aware of is GM cars from the 60s used an ignition switch that fed power to one circuit in run (the ballast resistor) and another while cranking (bypass to the coil). Because of this some LS swaps have some "creative" wiring to get 12V to the ecu in both run and crank.