Grounding stock gas tank

[Matt Cramer]

I've changed out the fuel gauge and sending unit - both of which were completely dead. Now, the gauge works, but the tank is empty when the gauge reads about 1/4 of a tank! I suspect the tank isn't well grounded. Should there be a ground strap on it somewhere?

[VetteVet]

Does the gauge read full with the tank full? If so take the wire off the sender unit and ground it to a good ground and see if the gauge reads empty. While the wire is off turn on the key and check the fuel gauge. It should go to way past empty to about the three o'clock position.

If it does then your float arm is out of adjustment or it may be hitting the side of the tank.Or you need to bend it up slightly, . You might want to take the sender out of the tank and ground the flange and with the tan wire on and the key on, move the float arm up and down through it's travel and see if the gauge reads empty and full.

[cool68]

still looking for info on grounding sender - any way to ground the top plate that the sender wire attaches to? or have to rely on tank grounding? where can extra grounding strap be attached to?

[cdowns]

ground anything to anything is possible if u understand what a ground is

it is not rocket science

[VetteVet]

The sender unit should automatically be grounded to the tank when it is installed.

The tank should automatically be grounded to the cab when it is bolted in place.

The cab is mounted on rubber supports with bolts in the center but it should be grounded to the engine and the frame with ground straps to ensure good grounding.

The engine is grounded to the battery by the negative battery cable mounted on a clean place on the engine. Then the engine should be grounded to the frame with a ground strap to a clean and tight connection

There are several other items that require grounding to these major parts, such as the dash cluster to the cab, the wiper motor to the cab and the radio to the cab. As well as all the lights to the frame or radiator support, If you have good clean and tight connections on these grounds your electrical problems will be greatly diminished.

As CD says "it ain't rocket science".

[mrein3]

Originally Posted by cdowns

ground anything to anything is possible if u understand what a ground is

it is not rocket science

Originally Posted by VetteVet

snip
As CD says "it ain't rocket science".

For the non-rocket scientists out there:
All a "ground" is on a 12 volt, negative ground automotive system is a return path to the negative side of the battery. Most if not all systems on a 12 volt auto need 12 volts to work. A "good ground" is simply a connection from your accessory you are trying to supply 12 volts through to the "-" post on your battery.
You can measure your ground by putting your digital multimeter (DMM) or volt-ohm meter to the ohms setting, putting one probe on the "-" post of the battery and the other on the spot you are checking, and seeing little or no resistance between your two probes.
Little or no resistance = "good ground".
Tons or infinite resistance = "bad ground".
Good ground = the light, stereo, you name the 12 volt accessory works
Bad ground = the accessory doesn't work.

To make a bad ground a good ground you need to figure out a clean path back to the battery. In your cab you need to make sure the cab is connected to the frame which has to be connected to the "-" side of the battery. An alternative path would be to connect the cab to the engine which should have a battery cable connected from it to the "-" side of the battery.

Like they said, this ain't rocket science. You just need a difference of twelve volts between the + and - side of the accessory you are trying to run which allows the electrons to flow from the + side of the battey through the accessory to the - side of the battery.

[Matt Cramer]

Originally Posted by VetteVet

There are several other items that require grounding to these major parts, such as the dash cluster to the cab...

Is that done through the harness, or a separate strap?

Yes, it does read full when the tank is full. But the thing is so rusty that I have to wonder about the condition of grounds in general. I wasn't sure if the tank had a separate strap to ensure grounding, or not.

[VetteVet]

The stock factory ground had a small cable with a metal clip connected from the cluster to the cab dash. If your gauges work and the dash lights come on then the cluster is grounded.

Yes, it does read full when the tank is full. But the thing is so rusty that I have to wonder about the condition of grounds in general. I wasn't sure if the tank had a separate strap to ensure grounding, or not.
________________

In order to get a reading the tank has to be grounded. If you're reading a full tank then most probably the resistor is OK on the sender but the float is not traveling all the way to the 0 ohms resistance on the bottom of the resistor. The arm is probably hitting the bottom of the tank and restricting it's full travel. That's why I suggested that you pull the sender and ground the flange and move the float through it's range and watch the gauge to see if it goes to empty. If it does then try bending the float arm up so that it moves further down before it hits the bottom of the tank. This will give you a longer full tank reading but it will be more accurate on the empty side.

[luvbowties]

Originally Posted by VetteVet

The stock factory ground had a small cable with a metal clip connected from the cluster to the cab dash. If your gauges work and the dash lights come on then the cluster is grounded.




In order to get a reading the tank has to be grounded. If you're reading a full tank then most probably the resistor is OK on the sender but the float is not traveling all the way to the 0 ohms resistance on the bottom of the resistor. The arm is probably hitting the bottom of the tank and restricting it's full travel. That's why I suggested that you pull the sender and ground the flange and move the float through it's range and watch the gauge to see if it goes to empty. If it does then try bending the float arm up so that it moves further down before it hits the bottom of the tank. This will give you a longer full tank reading but it will be more accurate on the empty side.

V-vette is spot on with that phrase "but it will be more accurate on the empty side"--as it IS the IMPORTANT side...the FULL side will take care of itself!
Sam

[Hawghauler]

Have you been inside the gauge cluster? I noticed when I redid my cluster that I'd bumped the fuel gauge needle and moved it unintentionally. Now my gauge is 1/4 of a tank fuller than the tank is. I'll correct this when I put a tach in, but until then I refill at 1/4 tank.

[Chaplain]

Originally Posted by VetteVet

The sender unit should automatically be grounded to the tank when it is installed.

The tank should automatically be grounded to the cab when it is bolted in place.

The cab is mounted on rubber supports with bolts in the center but it should be grounded to the engine and the frame with ground straps to ensure good grounding.

The engine is grounded to the battery by the negative battery cable mounted on a clean place on the engine. Then the engine should be grounded to the frame with a ground strap to a clean and tight connection

There are several other items that require grounding to these major parts, such as the dash cluster to the cab, the wiper motor to the cab and the radio to the cab. As well as all the lights to the frame or radiator support, If you have good clean and tight connections on these grounds your electrical problems will be greatly diminished.

As CD says "it ain't rocket science".

Originally Posted by VetteVet

The stock factory ground had a small cable with a metal clip connected from the cluster to the cab dash. If your gauges work and the dash lights come on then the cluster is grounded.




In order to get a reading the tank has to be grounded. If you're reading a full tank then most probably the resistor is OK on the sender but the float is not traveling all the way to the 0 ohms resistance on the bottom of the resistor. The arm is probably hitting the bottom of the tank and restricting it's full travel. That's why I suggested that you pull the sender and ground the flange and move the float through it's range and watch the gauge to see if it goes to empty. If it does then try bending the float arm up so that it moves further down before it hits the bottom of the tank. This will give you a longer full tank reading but it will be more accurate on the empty side.

Originally Posted by VetteVet

Does the gauge read full with the tank full? If so take the wire off the sender unit and ground it to a good ground and see if the gauge reads empty. While the wire is off turn on the key and check the fuel gauge. It should go to way past empty to about the three o'clock position.

If it does then your float arm is out of adjustment or it may be hitting the side of the tank.Or you need to bend it up slightly, . You might want to take the sender out of the tank and ground the flange and with the tan wire on and the key on, move the float arm up and down through it's travel and see if the gauge reads empty and full.

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