sending unit

[va_tlc]

my gas gauge doesnt work, i pulled the seat after grounding out the gauge on back of dash it worked, well i check the wire that runs to the sending unit and yep have juice there too, pulled aanother sender from a parts truck and hooked up b4 i droped it in the tank it worked while moving the float up and down ohh installed a new float also. well after i put it into the tank it wont work,,, forgot to mention while out of tank i grounded it against the tank, question is should i run a ground wire? or is it suppose to ground out when putting the metal hold down ring on? hope this is clear enuff for yall to understand thanks in advance, with 4.55 gears i just gotta know how much gas i have, or better terms dont have ohh and i looked for new sending units and it list 3 diff ones my cab is a 72 auto originally 6 cly 2wd... now its a 72 3/4 4 speed v8

[JHART]

there should be a ground that clips onto the sending unit. Is it there?

[northerngmc]

Take a look here.....

http://www.6066gmcguy.org/Electrical-02.htm

A good diagnosis on gas gauges.

I used it last weekend to fix mine.

Mine was a 69 GMC and I understand the 72's are a little different, but mine grounded through the ring that holds it in.

I would try holding a small piece of wire from the unit to the tank and see it that helps.

[GREASEMONKEY72]

mines a 72 and it just has the tan wire going from the tank to the gauge

[northerngmc]

I think the wiring is the same, but the piping to hook up the fule line is different.

[va_tlc]

thanks just got home, yea on my 72 theres just a single wire back to the fuse box, but as i looked at all 3 diffrent sending units 1 did have a ground wire also, im gonna try a extra ground today, cause when i had it outa the tank and grounded the sender to the tank it works, but drop it in he tank and no workie??? ya think the metal ring is suppose to ground it and its not doing like its suppose to work? thanks guys