Gas Gauge issues

[DoobieBrother]

Hello. New to the board. Just getting started on a `68 C10 handed down a couple of generations and needs a load of work.

Ok trying to fix the gas guage on this `68 C10. Father in law told me it needed a new float when I picked it up from him. I ordered one and this evening went about installing it. When I pulled out the old sending unit, all looked pristine including the little bag. I think maybe he already replaced it once. At any rate I decided to pull off the old float even though it looked fine. When I pulled it off I noticed it was heavy. So, I'm thinking ok, maybe it's waterlogged. Decided to put the new obviously light and hollow one on and just for curiosity sake float the old one in the sink. Old one sank except one corner held it up. Ok, maybe bad.

So, I put the new one in and reinstalled. Hit the key, and nothing. Well, here's what I noticed. Needle sits near "Empty" label. When you hit the key, though, it moves maybe a 1/16 inch or so further to the left (empty side). Unplug the sending unit wire from fuse box, hit the key and it goes all the way over to full+. Like 3 o'clock position. So, I'm trying to figure out...Bad sending unit? Maybe somehow positioned wrong? What?

Thoughts?

[jhow66]

Check here:
www.fix-a-gauge.com

[jhow66]

This should help also:
http://www.6066gmcguy.org/Electrical-02.htm

[68SHORTBOX]

If you take the wire loose from the sender and ground it does the guage go to empty?? If the guage reads past full at the 3:00 position when you connect it the sending unit is bad. Check the back of the fuel guage in the dash ground the guage and see if it reads empty. If not guage is bad. This may help with trouble shooting.

[GREASEMONKEY72]

is your tank still in the cab??? cuz mine would go to 3:00 position and then i grabed the wire and made contact again on the tank and its fine its only done that to me twice though but food for thought

[70c10]

If the new one reads empty it may have a bad float. The last sending unit I installed had a tiny break along the soldered joint and it was brand new. Take the new unit out and pop the float off and submerge it to see if it fills up or you see air bubbles. Just cuz it's new doesn't mean it's not defective. Good luck!

[DoobieBrother]

I got the following response on another board...

Sounds like a bad sending unit to me or it's missing the ground wire on the tank bung (Tank bung the round dealie) Should have a positive wire from the dash to the bung and a ground wire from the bung attached to the frame. You may have the wires on the bung reversed.

I responded with...

Doh! There's only one wire coming off the top of the sending unit. The positive. I was thinking the metal grommet made contact with the sending unit and the tank, and the tank was grounded by virtue of connection to the frame. Maybe that's it. Do you by chance have any pics I could check out?

I found this image...http://www.classicheartbeat.com/cata...ing%20Unit.htm

but I have no extra wire like that on the unit. I'll look tonight. I bet it's missing and I can add one in. I sure hope that's it.

...So, I'm thinking that may be it. Thoughts?

[wydomkr]

Dumb question, but how much gas is in the tank? I just replaced the sending unit on my 69, the tank had a bunch of crap in it, the sock was torn and the stem for the sender was plugged solid. When I put the replacement sender in, hit the key, it was still on empty. I thought crap, the used sender I had picked up was no good, but it looked like new. I went to the gas station, added gas and low and behold, it came up. It may not be 100% accurate, I don't know how much gas was in the tank to begin with, but it works. Mine only had the one wire for the power, no ground wire.

Keith

[LUV2XCLR8]

Originally Posted by 68SHORTBOX

This may help with trouble shooting.

Do you have this in a larger version?, very handy to have

If so please E-mail to luv2xclr8@charter.net (Subject 67-72)

[68SHORTBOX]

Will enlarge it and PM to you.