1980 242 wiring diagram

Looking specifically for where the green wire on the 8 pin connector on the main engine harness goes to. I've replaced the engine harness with an updated one, and am adding an oil pressure gauge. There is a green wire on the car side, but I can't see anything obvious under the dash as to where it goes. Trying to keep the install clean, and would rather not have a rats nest of wiring everywhere if I can use what is already there.

The green wire is used to provide power to the under hood light switch from fuse 8.

He's right. If you have an existing GREEN wire in that 8-pole plug (firewall), it goes to the fuse box for power to an optional engine compartment light.

Your 240 did not come with a green wire for a 2-wire oil pressure gauge, so you need to add one to the 8-pole plug and run it to the 'G' pole in the gauge.
Dave B
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You guys rock. Just the info I was looking for. Thank you.