One of my troubleshooting tenets is - what just happened?

Do not go swapping stuff as you may be introducing other problems.

You should check over all that you did when you pulled the engine and put it back.

Check all wiring that you took apart and make sure all your grounds have been restored.

Pull on some of the wires and see if they come apart. Maybe you broke one of them internally

WHAT ???? On our 88 745 GLE my daughter had a headlight out. A new headlight did not solve the problem. I had voltage at the plug but no light.

I pulled on each wire and one of them broke!

When I stripped the wire, I found a lot of black gunk, but only 1 strand of copper.

I got a new plug and the wires back to the firewall at the junk yard and connected it in to fix the problem.

I had 12 volts at the connector, but not enough current to light the bulb.