Hi everybody im a new member. I actually need some help with me project I swapped the cab out on my 94 300il 5 speed 4x4 the old cab was shot got an 80 cab for free have the dash and firewall modified but I ran the wiring and now my head lights wont turn off fuel pump keeps running and I have no juice to the key. HELP!!!!!!!! pulling my hair out cuz im on a deadline got to get my dads garage freed up

 

Sounds like you mixed the wiring harnesses between the 94 and the 80. Best bet now might be to get the wiring schematics for both vehicles and go by the color code as to what wire goes where. If thats what you did.. I just did that between a 91 cab onto an 87 pickup and had to swap wiring harnesses in the cabs to match the original pickup. But that was because the 87 was diesel and the 91 gas and wasn't too bad because they were pretty close to the same. The 14 yr difference in what you did would create a significant amount of wiring differences I would think.
You just have wires hooked together that shouldn't be and need to change them, figuring which ones is the time consumer.. Good luck

 

I actually gutted both cabs and used the dash harness and steering column from the 94 so it is all original to the truck. I have the engine turnin over
but I keep blowing fuses on headlights and fuel pump. any ideas on what they have in common just seems weird I blow both of them soon as I turn the key.

 

Sounds like you have wires crossed somehow.

 

And the only way to resolve it is pure grunt work. You'll need a good wiring diagram, then start tracing things through to find out where things got crossed up. I know you have a deadline, and that's probably making you feel rushed. But you need to work slowly and methodically through each circuit. Don't stop when you find one mistake. You need to make sure that everything is run correctly.

What's common between the headlights and the fuel pump? My guess would by nothing but the battery and the ground. So maybe you have the headlights connected to something that is +12 all the time and then the fuel pump and proper headlight lead connected to the same source. A short in the wire with the fuel pump would take out both fuses. I'm not saying that's the case, but it is an example of what could have been done.

While you're working through it you might get a second person to read the wiring diagram and step you through it one wire at a time. But it shouldn't be your best bud that your going through a half rack with while you work on it, nor should it be your gf making you think of other things completely. You need to be focused.

Good luck on it and let us know what you find out.

 

You may have some pinched somewhere too, make sure none got behind a column support or under something on a fenderwell