Fuel Gauge Pegged Past Full - HELP!

[Georgeb]

So cut that pink wire and ground to frame to test? Sorry I'm an idiot lol

yes, or find any place where it was spliced and open up the splice to get to the wire. Then ground it to the frame. If you can disconnect it from the top of the tank ground that connector.

 

[Georgeb]

post some pics of the wiring you are working with. that will help a lot.

 

[Mikee]

I just grounded the pink wire to the frame. Gauge moves to empty. What does this mean? What should I do next?

 

[Georgeb]

You need to double check your ground and signal connections at the tank. If that all checks out it is the sender in the tank.

 

[Georgeb]

How this works in a nutshell..... The gauge looks for a signal from the sender. The sender completes the circuit to ground a varying resistance depending on how full the tank is. By grounding the wire completely you completed the circuit with no resistance pulling the gauge to empty. for some reason the circuit is open. you need to find where it it open.

 

[Mikee]

How this works in a nutshell..... The gauge looks for a signal from the sender. The sender completes the circuit to ground a varying resistance depending on how full the tank is. By grounding the wire completely you completed the circuit with no resistance pulling the gauge to empty. for some reason the circuit is open. you need to find where it it open.

So the only possibility now is a bad ground (which I have cleaned and re attached) or the sending unit itself.

 

[Georgeb]

So the only possibility now is a bad ground (which I have cleaned and re attached) or the sending unit itself.

If you have taken the connection for the pink wire off the sending unit on top of the tank and grounded it successfully forcing the gauge to empty then yes, it is either the sender or the ground lead. Have you checked the connections on top of the tank?

 

[Oldrider]

Does it make any difference if the lights are on or off?

 

[chengny]

So the only possibility now is a bad ground (which I have cleaned and re attached) or the sending unit itself.

The 1980 dual tank control circuit is kind of involved...

The PNK 30 lead - from the gauge - transits the firewall at the main bulkhead connector. That lead is then run way back to the area near the transfer solenoid. In that area it is spliced to a TAN wire - which is then lead all the way back to the firewall and to the dash mounted selector switch.

When the switch is toggled - to whichever tank is to be used - the contacts for one of two sender leads are closed. The selected lead then runs all the way back to the associated sender. These two leads are TAN/WHT or LT BLU.

The point is that the the loss of continuity in the sensing side of the circuit may be occurring in the dash selector switch.

Splice an extension onto the pink lead - eliminating the switch completely - and run the extension to the senders hot terminal. See what happens then.

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[Mikee]

The 1980 dual tank control circuit is kind of involved...

The PNK 30 lead transits the firewall in it's own grommet. That lead is then run way back to the area near the transfer solenoid. In that area it is spliced to a TAN wire - which is then lead all the way back to the dash mounted selector switch. When the switch is toggled - to whichever tank is to be used - another lead then runs all the way back to the sender. These two leads are TAN/WHT or LT BLU.

The point is that the the loss of continuity in the sensing side of the circuit may be occurring in the dash selector switch.

Splice an extension onto the pink lead - eliminating the switch completely - and run the extension to the senders hot terminal. See what happens then.

You must be registered for see images attach

Wow that is a lot of knowledge. We have dropped the fuel tank and are in the process of replacing the sending unit itself. If this does not fix the problem, I will try what you said. So can you explain in detail which wires I need to run? I am a bit slow when it comes to this stuff LOL!

 

[chengny]

Wow that is a lot of knowledge. We have dropped the fuel tank and are in the process of replacing the sending unit itself. If this does not fix the problem, I will try what you said. So can you explain in detail which wires I need to run? I am a bit slow when it comes to this stuff LOL!

Wow that is a lot of knowledge.

On the other hand, it might be a lot of ******** - you never know.

By grounding the sensing leg and getting an "E" reading on the gas gauge, you have confirmed that the PNK 30 lead is good - and that the gauge reacts low.

The fact that the gauge read high ("F") when the PNK 30 was not grounded - proves the gauge is good at the other end of the scale.

Whether you change the sender or not is your call, but it may not be bad. I would test the currently installed unit first.

I don't really know how that PNK 30 is run, but it may be in the same conduit that the leads to the rear lighting use.

The issue will be finding where the PNK 30 is spliced to the TAN 30A. When you locate that splice make an extension lead and connect it to the end of the PNK 30. Forget about all the rest of the wiring - since you have removed the extra tank it is all useless.

Once you have a long enough lead - that comes directly from the dash - connect the free end to the brass post on the sender. Turn the ignition switch to RUN, cross your fingers, and observe the gas gauge.

 

[MarshMobbin907]

The 1980 dual tank control circuit is kind of involved...

The PNK 30 lead - from the gauge - transits the firewall at the main bulkhead connector. That lead is then run way back to the area near the transfer solenoid. In that area it is spliced to a TAN wire - which is then lead all the way back to the firewall and to the dash mounted selector switch.

When the switch is toggled - to whichever tank is to be used - the contacts for one of two sender leads are closed. The selected lead then runs all the way back to the associated sender. These two leads are TAN/WHT or LT BLU.

The point is that the the loss of continuity in the sensing side of the circuit may be occurring in the dash selector switch.

Splice an extension onto the pink lead - eliminating the switch completely - and run the extension to the senders hot terminal. See what happens then.

You must be registered for see images attach

I have this exact issue. So you're saying oink runs to tank but spiced off before tank is brown 30a and that leads to switch. You're saying eliminate 30a basically?

 

[echo7bravo]

I have this exact issue. So you're saying oink runs to tank but spiced off before tank is brown 30a and that leads to switch. You're saying eliminate 30a basically?

Are you running dual tanks? I think what Jerry is saying is that if your tank is pegged past full you have an open circuit. If you ground out the circuit pink or even tan 30A to a known ground the gauge should shoot over to empty. If it does in fact do that then you know your pink/tan link is good and that your ground from your sending unit to your frame is not grounding good.

 

[MarshMobbin907]

Are you running dual tanks? I think what Jerry is saying is that if your tank is pegged past full you have an open circuit. If you ground out the circuit pink or even tan 30A to a known ground the gauge should shoot over to empty. If it does in fact do that then you know your pink/tan link is good and that your ground from your sending unit to your frame is not grounding good.

I apologize, didn't see the notification. I am running dual tanks but it doesn't switch to my passenger side. Every now and again my fuel pump on driver side will lose power, I'll have to crawl under and wiggle the connector then the pump starts working, even the gas gauge starts to work every now and again when I do that.

 

[foamypirate]

I apologize, didn't see the notification. I am running dual tanks but it doesn't switch to my passenger side. Every now and again my fuel pump on driver side will lose power, I'll have to crawl under and wiggle the connector then the pump starts working, even the gas gauge starts to work every now and again when I do that.

If you lose a ground, the fuel pump will stop running. Sounds like the ground may be your issue if that fixes both the pump operation and the gauge function.