78z Fuel Gauge is not working

[gotham22]

I did a bunch of searches but I am still unsure how to test the system properly.   My fuel gauge is not moving.  It had previously worked.  So I have a few questions:

1- How can I test the gauge on the bench to make sure it is not an issue with gauge itself?

3-When the wires are disconnected from the fuel sender is there a way to test and see if the gauge moves?

2-Anything else I should know?

 

I attached the two pictures, the wires at the sender and the gauge

Thanks in advance for your help.  

 

[Yarb]

Ground the sending unit going to the gauge. It should swing all the way to the full position.

@SteveJ please correct me if I have lost my mind which is very possible!!

Edited May 7 by Yarb
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[SteveJ]

12 minutes ago, Yarb said:

Ground the sending unit going to the gauge. It should swing all the way to the full position.

This test should only be done with the gauge in the car. The voltage regulator needs to be connected for the gauge to function properly.

@gotham22 Here is a video of setting up a bench test. Follow the wiring exactly. If you're not sure how it should be wired, stop and ask questions, otherwise, you could damage a gas gauge. 

 

 

12 minutes ago, Yarb said:

@SteveJ please correct me if I have lost my mind which is very possible!!

I have not been able to ascertain the state of your sanity.

[gotham22]

Ok so I will test it with the gauge connected in the car.  How do I ground the sending unit to the gauge?  Sorry for the dumb question.  I am not a wiring guy and I don't want to mess anything up.

 

 

[Yarb]

My Sanity is in question so I will have to surrender to @SteveJ

[SteveJ]

9 hours ago, gotham22 said:

Ok so I will test it with the gauge connected in the car.  How do I ground the sending unit to the gauge?  Sorry for the dumb question.  I am not a wiring guy and I don't want to mess anything up.

You have to use a small piece of wire to jumper the black and yellow terminals where the wiring connects to the sending unit at the tank.

[gotham22]

So I jumped black to yellow and then black to yellow/blue.  The gauge did not move.  I tried this with two different gauges. I guess thats good news that it is not the gauge or the sending unit.  Where should I look next?  

[Yarb]

@SteveJ If I may, most probably in the harness. Have not gone back in the thread, did you test the gauge itself?

[SteveJ]

11 minutes ago, gotham22 said:

So I jumped black to yellow and then black to yellow/blue.  The gauge did not move.  I tried this with two different gauges. I guess thats good news that it is not the gauge or the sending unit.  Where should I look next?  

Was the key in ON?

[gotham22]

Key was in the on position

[gotham22]

I have not bench tested the gauge yet

[SteveJ]

Is there any chance that the dash harness to body harness connector was disconnected?