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Does the wire that go's to the fuel meter have 12v all the time an shuts off when the key is turned off?? Cause on my truck it shows it with power at all times,,

The wiring diagram is a pain, but I think yes, the power comes off the gage fuse and goes to the gage and then grounds at the tank sensor.

The power does come from the gauge fuse, however it should go off with the ignition.

Ya that's what i thought. On with key off with key, hmm guess ill have to frind that wire.. the truck only had 7 wires going back there. 2 of tham have power with the key off. I found the park, brake, lite wires. I think i have found the turns, but not sure sence they dont flash. Lol but ok ill keep trying.

If anyone can help that would be awesome .......
I dragged this truck out of a junk yard. Its a 79. Most of the wiring was missing or had been cut off. I put a 305 in it an im tryin to utilize most of the wiring that i can. I noticed two small plugs that lead wires down an back to the back of the truck.
Well i cut most of that off cause it looked like a rats nest under the bed. I replaced it with 7 wire trailer wiring. I have found both turns/brake/park. I have one wire that pulses an one that turns on when the key is being turned in crank/start. Once the key is in the run position it turns off. I have tryed looking at all kinds of diagrams an they dont really help..
If you have any clue about where the pulsating wire go's an the one that turns on an off with the key.

Honestly the one that pulses I would have guessed to be the fuel pump wire although I don't know why it would pulse or why it would shut off once the engine is started. Sounds more like a starter wire with a bad connection but I wouldn't know why it would be running to the back of the truck.

This ones got me stumped.

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When in doubt floor it. If you can't floor it then you've doubted yourself.

The wire that pulses would be the one to the fuel sender in the tank. The one that goes on in the start position only would be the fuel pump wire. It is powered in the start position and then is powered by the fuel pump relay after the engine starts.

Ok that makes sense. So i think i have it wires right then lol.. ill just eliminate the fuel pump wire back there sense the motor has it on it. . Thanks guys

Shouldn't the fuel sender wire be a constant voltage? The fuel guage sender works by resistance and the guage itself measures that amount. I would think the pulsing wire would be to either the turn signal or hazard lights and one of those switches just happens to be ON.
You may just want to save up some money and get an aftermarket harness if yours is hacked up as much as it sounds.

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I've never been wrong! Once I thought I was, but I was mistaken.
Rick
Loranger, La
1980 Stepside LUV (Again)

Well i found the left/right turn wires. Park an brake wires. An from what i could tell on a diagram i have the rite wire for the sending unit. An it shows or says YR for the sending unit. An that's the wire that pules soo. The plugs were there in the engine bay that went to the back of the truck along with the wires. It was under the box were it was a HUGE rats nest lol.. if i can figure out how to post pics from my droid phone, sense that's how i have internet i would have to show lol

The gauge regulator is a pulsing type regulator. It pulses at about a 1-2 per second rate or so and supplies power to the fuel and the temperature gauges.
The gauge movements are dampened and can't follow the rapid pulse movements so they get an average voltage of about 8 volts. The sender unit in the tank completes the ground circuit and would help dampen these out. But with an open circuit I'm sure you would see the pulses.
Maybe more information than you wanted but just trying to help a bit.