1974 Dual Gas Tank Ground

[mntoy]

The fuel gauge recently quit working and is pegged past full. I have read on this site that this is either a bad ground or bad 12v power wire. I got under the truck and cannot find where the ground is located for the tank/tanks. Is it located under the tank/tanks or am I simply not finding it? Is there one ground for each tank? Do I have to find it? If it is a bad ground can I simply attach another ground wire to the middle of the tank/tanks where both halfs seam together and connect that same wire to the frame? Any help would be great.
Thanks,
Mike

[Irish_Alley]

if you get a bad reading from both tanks and this happened at the same time i would think its a broken wire between the selector valve and the gauge. might even be in the switch

[Takilma]

Mike,
I haven't had one in front of my face yet, but others on this forum state that the grounds on the fuel tanks are "up top" and you must drop the tank or pull the bed. You could try your idea of grounding at the seam BUT, EXTREME CAUTION! if you are drilling on or any where near the tank, gas (or fumes) may penetrate that fold further than you think, I would use some kind of clip or crimp. Also I don't know if it's the tank body that grounds or the actual pickup/gauge unit assembly...hopefully one of the more knowledgeable readers will have better data for you... 

[mntoy]

I have not used the second tank in years (mostly due to gas prices and the cost to fill both tanks at once) and the tank selector is a push/pull cable. I dont know if the fuel gauge would work if I switched to the second tank. I mentioned tank/tanks because I was not sure if each tank is grounded separately or the ground was wired together and to the frame in one location. If each is grounded separately and the grounds are above the tank that is why I cannot find them. Hopefully someone who has done this recently on the older model truck will chime in. Also I never thought about drilling through the seam and causing an explosion, thought it was just extra metal to ground to. Again anyone actually perform this check recently?

[Irish_Alley]

the ground should be attached to the sending unit to the frame.
this might help you but it not the same year.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=9294.msg62470#msg62470
how the fuel tank selector valve is controlled by a cable is the gauge the same way? meaning if you pull on the cable it switches the tank for fuel and the sending unit? i never touched one of these old styles

[hatzie]

Each tank is grounded separately at the sender.  I believe the cable system still had a dash switch to control which sender feeds the gauge.

[mntoy]

Irish,
Thanks for the reference to the previous post on dropping the gas tank. From the pictures in the post it looks like there is one wire to the sending unit itself and the ground wire is attached to one of the bolts that holds down the ring around the sending unit. Based on the pictures I am going to try to attach a second ground to the side of the tank before I drop the tank and check the wires at the sending unit. Unless someone else knows better.
Thanks again,
Mike

[enaberif]

Just leave it on the sending unit but put new grounds on and extend it so you can drop the tank with grounds attached.