Hi i just bought a project Volvo 740 turbo. The previous owner did some weird things to some of the wiring witch leads me to a problem. When I have the key in and turn it over to start it makes a popping sound and then turns off. Non of the lights work after. I have to unplug the battery for everything to go back to normal. I’m guessing this is a wiring issue if anyone has any idea please let me know.

 

1987 is bad year for the Volvo wiring harness. What was done by the PO? You have to replace parts of the harness, not cheap, or splice in and wrap individual wires which is fiddly and doesn't work great or lasts.

Post more info, pictures, etc.

 

From what I can tell the previous owner had put a Saab Ecu but nothing is connected to it, did a ac delete, installed a aftermarket cold air intake. He said it runs and drives but I’m having a hard time believing that. I don’t think anything is wrong with the harness but I could %100 be wrong. Ik some wires are not connected but I should still turn over right? My guess is it’s a starter or solenoid because I hear a click sound but then everything turns off almost like a safety feature. If u need any info or pictures just ask

 

You can see the wrapped wires, so the PO did address that, for starters... The rest, hard to say. You may be right about the starter--test it by measuring voltage going to it when you turn the key. Don't envy you, looks like quite a project!

 

weird, that oil filter looks like the configuration used on turbo 740/940.

 

Turns out that the solenoid connectors where rotted really bad and causing it to get no electricity. Thank you for the help.