gas tank sending unit

[hdixon]

Can anyone shade a little light on gas tank sending unit. I have a LMC 20 gallon gas tank rear mounted that I installed and am a bit confuse or loss on how the sending get it's power. I've notice that there is a black wire on connected to the top ring and appears to be a ground wire. where dose the positive 12v power from? Do it come form the dash bezel and all I need to do is make sure the unit is grounded not sure any help would be great I am loss again.

[VetteVet]

Originally Posted by hdixon

Can anyone shade a little light on gas tank sending unit. I have a LMC 20 gallon gas tank rear mounted that I installed and am a bit confuse or loss on how the sending get it's power. I've notice that there is a black wire on connected to the top ring and appears to be a ground wire. where dose the positive 12v power from? Do it come form the dash bezel and all I need to do is make sure the unit is grounded not sure any help would be great I am loss again.

The power to the gas gauge comes from the fuse panel when the key is on and goes to the cluster plug for the dash and then to the gas gauge.


The gas sending unit does not get any power, it is a path to ground for the gauge. the arm on the sender is connected to a variable resistor to ground and it changes the connection to ground as it moves up or down with the amount of gas in the tank.
Think of it as a light bulb with power to the light bulb (gas gauge) and a ground from the bulb (sender wire) that has a lot of resistance to ground or little resistance to ground. IF the resistance is high the bulb will be dim (gauge reads full) and if the resistance is low the bulb will be bright, (gauge reads empty).

The gas gauge sending unit wire runs from the gauge back through the fuse panel down under the drivers sill plate to the gas tank sending unit. The sending unit is grounded to the tank which must be grounded to the frame to finish the circuit.


Hope this helps.

[rockyrivermark]

Don't run a full 12v power to the sender!
On the top of your fuse panel there is a connector that's says fuel.
It's a lower voltage power for the sending unit.
Run that to other wire (not ground) on sender.
Mine also needed a ground from the sender to chassis.
Also give vehicle info. Sometimes these things are year specific.

[hdixon]

Originally Posted by VetteVet

The power to the gas gauge comes from the fuse panel when the key is on and goes to the cluster plug for the dash and then to the gas gauge.


The gas sending unit does not get any power, it is a path to ground for the gauge. the arm on the sender is connected to a variable resistor to ground and it changes the connection to ground as it moves up or down with the amount of gas in the tank.
Think of it as a light bulb with power to the light bulb (gas gauge) and a ground from the bulb (sender wire) that has a lot of resistance to ground or little resistance to ground. IF the resistance is high the bulb will be dim (gauge reads full) and if the resistance is low the bulb will be bright, (gauge reads empty).

The gas gauge sending unit wire runs from the gauge back through the fuse panel down under the drivers sill plate to the gas tank sending unit. The sending unit is grounded to the tank which must be grounded to the frame to finish the circuit.


Hope this helps.

I am going to use a painless wiring harness p/n# 10206 I see a place on the fuel panel for a electric fuel pump but nothing as far a sensor anyone have this type of wiring harness that you know?

[VetteVet]

Originally Posted by rockyrivermark;8447756[B

]Don't run a full 12v power to the sender! [/B]
On the top of your fuse panel there is a connector that's says fuel.
It's a lower voltage power for the sending unit.
Run that to other wire (not ground) on sender.
Mine also needed a ground from the sender to chassis.
Also give vehicle info. Sometimes these things are year specific.

I can't stress this too much, putting positive voltage on this wire and connecting
it to the fuel sender is a direct path to ground AKA a short. Although it runs through the intank resistor, it will create heat in the resistor windings, and depending on the position of the arm, the resistance to current will be enough to make the windings heat up enough to possibly ignite any fuel vapors in the tank.

[hdixon]

Originally Posted by rockyrivermark

Don't run a full 12v power to the sender!
On the top of your fuse panel there is a connector that's says fuel.
It's a lower voltage power for the sending unit.
Run that to other wire (not ground) on sender.
Mine also needed a ground from the sender to chassis.
Also give vehicle info. Sometimes these things are year specific.

Thanks and I understand what you are saying about the sending unit and a direct 12v however I am going to be installing a painless wiring harness and it only shows a electric fuel pump not a sensor port on the fuses panel

[VetteVet]

Originally Posted by hdixon

Thanks and I understand what you are saying about the sending unit and a direct 12v however I am going to be installing a painless wiring harness and it only shows a electric fuel pump not a sensor port on the fuses panel

Do not worry about the missing FUEL terminal on the fuse panel. It is merely a connection point for the sending unit wire to connect the sending unit to the fuel gauge. You can connect the two wires with any removable connection as long as you don't ground the connection or either end of the wire.
A solid splice would work but you would have to cut the wire if you ever needed to remove it.

You must not be using a fuse panel designed for your year truck since the 67 to 72 did not have an electric fuel pump. I noticed that you didn't say what year truck you have but you described the sender for a non electric pump sender in the tank. VV

[hdixon]

Originally Posted by VetteVet

Do not worry about the missing FUEL terminal on the fuse panel. It is merely a connection point for the sending unit wire to connect the sending unit to the fuel gauge. You can connect the two wires with any removable connection as long as you don't ground the connection or either end of the wire.
A solid splice would work but you would have to cut the wire if you ever needed to remove it.

You must not be using a fuse panel designed for your year truck since the 67 to 72 did not have an electric fuel pump. I noticed that you didn't say what year truck you have but you described the sender for a non electric pump sender in the tank. VV

thanks for all your support with this issue

[michael bustamante]

are you running a under the bed tank or behind the seat tank? if behind the seat I have a good fuel guage wire up for sale. good connectors.

[hdixon]

Originally Posted by michael bustamante

are you running a under the bed tank or behind the seat tank? if behind the seat I have a good fuel guage wire up for sale. good connectors.

I am running a under bed gas tank from LMC

[michael bustamante]

ok well if you need this sending unit wire you can lengthen it and itll work for you. 12.00 shipped to you. theres apic of it in the for sale section under misc. wiring

[hdixon]

if you take 10.00 its sold

[michael bustamante]

sure why not... help a brutha out..pp is
sidestep1967@gmail.com

[hdixon]

Originally Posted by michael bustamante

sure why not... help a brutha out..pp is
sidestep1967@gmail.com

I can't find the pic of the wire

[hdixon]

Originally Posted by michael bustamante

sure why not... help a brutha out..pp is
sidestep1967@gmail.com

Hi Mike had a little family problem but do you still have the sending unit connector?