Chevy & GMC Vans

The manual I am using says I need to disconnect a brown wire before setting the timing. I can't seem to find this wire. I know you are supposed to disconnect the advance so you can get an accurate setting but don't know how to do that. Can anyone make a suggestion?

Thanks

If you track along the wire harness from the ignition control module in the distributor, you should find a single wire with a connector. Decoupling this connector is how you unplug the brown wire. Going from memory here, this disconnect is like 8 or 12 inches away from the distributor in the wiring harness.