68 GMC Sierra fuel gage/electric
 

Greetings
1. My friend’s 1968 GMC Sierra fuel gauge is not working, I checked the wire from sending unit to the fuse box it was good, however the wire connection to the fuel box have no electricity at all (it plugs to the top of the fuse box it indicates fuel gauge)
Anyone knows why no electricity and how to check/fix/resolve it?

2. As I know, the 1968-1972 sending unit has only one fuel port that goes to the fuel pump, this truck has 2 ports, one is venting hose, however it’s inside the cab, and cab smells fuel.
Do I cap it, or do I extend the hose to outside and where?

Note: this truck is fully restored.

Thanks

Re: 68 GMC Sierra fuel gage/electric
 

This should get you through your fuel guage issue.

http://67-72chevytrucks.com/vboard/s...d.php?t=640615

I am not much help with the fuel port, except to encourage you to do a search using the box above. I know there are lots of threads about this. Year and whether it was a California truck make a difference too.
Good luck.

Re: 68 GMC Sierra fuel gage/electric
 

HO455, thanks for your help

Re: 68 GMC Sierra fuel gage/electric
 

Just so you know, there was no such thing as a GMC Sierra in '68. That trim package came along later.

Re: 68 GMC Sierra fuel gage/electric
 

The sender with two ports is for a 72 if I remember correctly that extra would go the the purge canister witch you don't have . BUT if you have the right gas cap for your year it is vented and then if that indeed is the case you can plug that port with a vac cap no problem. Jim

Re: 68 GMC Sierra fuel gage/electric
 

Thanks for info,
This one has Sierra Grande on the side, and on the glove compartment,

Re: 68 GMC Sierra fuel gage/electric
 

The wire to the top of the tank is a ground wire, the 12 volts comes into play behind the dash at the gauge and to the fuse panel.

Re: 68 GMC Sierra fuel gage/electric
 

The problem is that no indication at the fuel gage, the fuse beside where the Tan wire (coming from sending unit) is not workin. My knowledge this wire your taking about (on top of sending unit) should be the 12v, sending unit is grounded by the tank.
Temp gauge is moving slightly when engine is idling

Re: 68 GMC Sierra fuel gage/electric
 

I’ve a 72 and it only has one port,
For this truck, I’m not sure about fuel cap.

Re: 68 GMC Sierra fuel gage/electric
 

Nope it's a ground wire, the tank to the body just completes the grounding circuit. The negative feed from your battery to the sending unit in this illustration is completed by your metal tank to the cab/body, the wire from sender to gauge is a continuation of that grounding to complete the grounding circuit.

https://auto.howstuffworks.com/fuel-gauge1.htm