Fuel Gauge help - am I stupid?
 

Morning all and Happy Fathers Day!

Apologies for the radio silence, still here, still pick away, but a small challenge at home has meant I have not been as active on here as late.

Anyway, I needs some help.

Background.

Have moved my fuel tank to the back of the truck using a Jeep tank and a Blazer fuel basket and sender.

Deluxe dash.

Rewired using a loom that I cant remember sitting here at my desk.

Anyway, fuel gauge didn't work. Tested wiring and gauge and deducted gauge faulty.

Ordered new gauge and box of tricks to enable old gauge to work with new sender.

Installed both.

Gauge now goes to full whatever I do with sender.

Tested Continuity - all good.

Tested voltage across gauge - 12 volts?

So... This is my questions (s)

Which wire goes where on the gauge - picture below.

https://67-72chevytrucks.com/vboard/...1&d=1749989013

Should there be an insulator that goes between the gauge and the metal 'pod' it fits in to stop the gauge earthing out against the 'pod'?

I have the insulator that goes across the terminals once it is bolted into the 'pod'.

It feels as if I am missing something but my brain is too tired to work it out.

Hopefully it is just me being stupid and quite happy for me to be told the error of my ways.

Any help and advice always welcome and appreciated.

P. :D

Re: Fuel Gauge help - am I stupid?
 

Usually pegged full is a no ground situation. Do you have a ground wire from the sender to the frame of the truck?

Re: Fuel Gauge help - am I stupid?
 

Thanks Roger.

It is the same earth as shared with the electric fuel pump so should be good but will check.

Does the gauge have to be grounded to work as at the moment it is all hanging lose.

P. :D

Re: Fuel Gauge help - am I stupid?
 

Can you load the pic of what you're doing? It may help.

Re: Fuel Gauge help - am I stupid?
 

The sending unit is a variable resistor that takes a positive signal from the gauge and grounds it with variable resistance to control the needle position...a quick test would be to ground the wire at the sending unit...that will send the gauge all the way one way...disconnecting the wire and not grounding it will send the gauge all the way the other way...that will tell you the gauge and wiring are more than likely ok...if there is no reaction then a wiring or gauge problem exists...if there is power at the sending unit it comes from the gauge...that is an indication the wiring is ok as long as the ground to the sending unit is good...

the gauge itself provides power to the sending unit.
(I've always felt the term 'sending unit' is a bit of a misnomer)

The sending unit has only two connections:
- to the gauge "S" terminal
- to 'ground'

The gauge works by measuring how much current flows
from the "S" terminal, through the sending unit,
to ground.

If the gauge is not being supplied with 12V power from the ignition switch,
it can not supply any power to the "S" terminal.

Re: Fuel Gauge help - am I stupid?
 

Sorry for the late reply Gents, my children all came home, fired up the Braai and provided me with burnt offerings for being Dad.

Nice.

Anyway. This is what I think I have worked out.

If I ground the wire to the sender I get full movement.

Gauge, Wiring, Sender unit are all new.

I 'think' the issue is that the gauge is not grounded through the dash panel as it is currently floating in free air as I wanted to make sure everything was working before re assembly.

Therefore, when I switch the ignition on the gauge goes to full as it is not earthed.

As I am now full of meat and 4 beers deep will check my theory by putting it all back together in the morning, as now have 2 weeks off.

Will report back on my findings with either a confirmation that I am stupid or a plea for help.

Enjoy your Sunday.

P. :D

Re: Fuel Gauge help - am I stupid?
 

Here’s a couple good YouBoob videos

Brothers: Short and sweet, 6 mins
https://youtu.be/ZTMXjITuO8A?si=sEashzvQXiIKLnDf

LMC: a bit more detailed, 19 mins but for newer C10’s, still good troubleshooting info
https://youtu.be/Bq3YfCLq4So?si=S1TGB6r0Br-X1Yto