'78 fuel pump turns on when brakes pressed

[Quintanamobay]

Hello everyone.

I have a 78 bay window, converted to carbed. I have never been able to get the tail lights working right, finally bit the bullet and had a shop look at it. They said it appears there was a fire at one point and a ground or lead must have melted. They recommend having the main harness replaced. I bought this car as a project and I would like to try to fix it myself before paying them to rewire it. Problem is, I am a total amateur at this.

As of right now, headlights, blinkers, emergency flashers for the front all work as expected. when you have the headlights on, car off no key in the ignition and press the brakes, the fuel pump kicks on.

Can anyone point me to a guide, or explain to me how I may go about tracking down the issue? All I can figure right now is maybe it is hooked up wrong up front. I found fuse box diagrams online and it tells you what circuits are attach to what terminal. Does it matter what plug on the terminal you use?

Thanks!

Edit: In the Haynes repair manual, the newest wiring diagram is for 72 onward. Does that diagram apply to my bus?

[Randy in Maine]

How do you have the fuel pump wired up?

[Quintanamobay]

[KentABQ]

[Tcash]

This is how you read the wiring diagram.

[Abscate]

Ill guess the brake lights are shorting to the reverse lights are shorting by back to the coil , which is incorrectly wired and the hot side is supplying fuel pump current via your wiring

You can try pulling the reverse light connector off but a melted loom could be shorted anywhere so it’s a weak diagnostic

Run a new wire with a fuse from B+ to your fuel pump would work , though.
_________________
.ssS!

[Ghost Rider Llc]

Just had the same problem on my new to me 76. Someone had replaced the brake bulb with a single filament bulb 1156 instead of the two filament bulb 1157. With the lights on and car not running it would power on like it was running “eg fuel pump running”. Plus the brake light didn’t work. Change bulb all good. Hard to believe one bulb could do all that.

[Quintanamobay]

[Abscate]

That’s very common for cables or connectors to go bad.

Take some pictures of your battery connections so we can tell you how ugly they look.

Warning! The first step of any electrical work is to ALWAYS remove the negative battery terminal so that you don’t cause any more damage.

OLD VWs have several circuits that aren’t fused, so if you touch one of these to ground, you burn your harness somewhere in your Bus that you can see, or maybe you burn the whole Bus.

If you had a wiring fire your entire loom is a ticking time bomb waiting for melted insulators to Touch somewhere. You can you tube shorting auto battery to see what this looks like.
_________________
.ssS!