84 ram 250 gas gauge testing?

[comet240]

hi a couple years ago i was redoing the camper top of my van and i redrilled holes in it but didnt know i drilled into the electrical, well i fixed all the wires i figured but the gas gauge still doesnt work so i wanna know how do i test it really at the pump i see the connector wire for the gas gauge u can pull it off but anyone know what i should be getting at the pump etc so i know if the wire is gone or if the pump gauge is gone or if the dash's gauge is cooked since i cant buy a fuel gauge anywhere just to test it. only oil prssure water amp and volts

[alloro]

The fuel sending unit runs on 5 volts. There's a wire (usually light blue) that runs from the instrument cluster connector to the sending unit. The second side of the sending unit is grounded. Because of this, you can test the sender wire for the 0-5 volts of power, but the power will remain constant unless you can change the level of the float within the gas tank.

The easiest way I've found to test it (short of removing it) is to disconnect the sender wire and connect an ohmmeter from the sender to ground. Once you have this all connected, go to the gas station and start putting fuel in. As you're filling, you should see the needle move on the ohmmeter if the sender is good. The downside to this test is if you end up having a bad sender, you just added gas to a tank that you have to take out.

[comet240]

ah ok ill try that so at the gas tank check if i get 5 volts or a ohm meter, so if that works ll just run a new wire under the van to the dash then just a beotch to take the dash off

[comet240]

ok i took the instrument panel out broke damn sperdomiter cable cuz it didnt coome out and i couldnt reach around so hopefully it works once i put it back in but at the gas tank there is a light blue cable that goes to the center of the pump and the other is just a clip on one witch is the gauge? and if its the center one at the cluster there is no sold light blue there is a light blue with a black strip any info guys

[alloro]

Originally Posted by comet240

at the gas tank there is a light blue cable that goes to the center of the pump and the other is just a clip on one witch is the gauge?

Actually both are for the sender. In 1984 the fuel pump was mechanical and mounted to the side of the timing cover, there is no pump in the gas tank. The blue wire you found comes from the gauge and the wire with the clip is just ground.

At the cluster the light blue with the black stripe wire is the one that goes to the sender. There is a connector where the color change takes place just before the wire exits the body through a rubber grommet.

[comet240]

ah ok but the wire with the cap is the blue wire the other wire on the side i figured that was the ground then and the center wire with the cap be the power wire or i guess not right

or maybe as power gets sent to the center and the return wire is outside but just verify for me

what i see is
center wire cap has a blue wire and clips onto a bolt
the side wire is unshielded and just a regular push on clip wire and that looks black but got old grease on it so i dunno where that wire goes anyways

[alloro]

The blue wire runs to a connector where it turns into a blue/black wire and then runs to the fuel gauge, the black side wire is just a ground and goes to a bolt on the body somewhere nearby.

The +5v goes to the gauge, the second side of the gauge goes to the blue/black wire to pick up a ground. The sender in the tank is a variable resistor to ground, not power. If you were to remove that blue wire from the sender and ground it, your gauge (key on) would shoot up past full.

[alloro]

Here is a general diagram of how a fuel gauge and sending unit is wired. Perhaps a visual will help.

[comet240]

ah ok now i see ya so center one is the postive wire so power goes from the guage to the tank not the other way around i thought

ok so ill clip off wire from the blue by the tank and the light blue black in the dash then

correct

[alloro]

Originally Posted by comet240

ah ok now i see ya so center one is the positive wire so power goes from the gauge to the tank not the other way around i thought

ok so ill clip off wire from the blue by the tank and the light blue black in the dash then

correct

Yes by George I think he's got it! LOL

Before you replace the wire, do as I suggested and touch the blue wire at the tank to ground. Then turn the key on and see if your gauge goes up. If it does the wiring is okay and the sender is bad. If it doesn't, then you know the wire is no good.