i have a 1990 cummins 3/4 ton, and im having a problem with my electrical, the first problem is that my entire engine and my whole body always has power to it? and second is when i pull the switch for my head lights they dont turn on, but i have this buzzing sound? and is it normal if when i unhook my battery terminal my truck should turn off?

Thanks, DoubleNicoll

 

What on the engine is always powered up?

The headlight switches on these truck are a known weak point. Throw a switch at it, they're under $15 at most auto parts stores.

Yes, the truck should die if you unhook the battery. The fuel shutoff solenoid needs at least 8 volts to stay open.

 

Yeah, what part of the engine are you getting a voltage reading from? Where are you putting the leads from the voltmeter? How many volts are you seeing?

In a normal world, the engine/frame/body is the ground so I don't know how you'd be getting positive voltage on the block.