Gas gauge has me stumped?

[Got Smoke?]

My gas gauge has me stumped on my 79 K20. My cousin worked on it today while I was at work but here's what we've covered so far.
1) ground wire for sending unit was unbolted cleaned with wire brush and reinstalled. No effect.
2) All fuses were checked wih a test light and were fine.
3)The signal wire was cut between the tank and where it goes into the wire loom up by the starter. the reason for this was because I've had to bad spots come up in that short run of wire there before so we were thinking some moisture might have gotten into the butt connectors where my splices were.

Still no change gas needle is sitting in the 3 o'clock position and there is hardly any gas in the tank? Help!

[Captkaos]

Have you read this, this is a POPULAR topic.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=9072.0

[VileZambonie]

Since you say it's up by the starter I assume this is a single right hand tank? Ground the sending unit wire key on engine off (KOEO) and see if the gauge reacts.

[Got Smoke?]

Yeah its a single 20gal pass side mount tank. I will have him try grounding the sending unit wire today. I tried reading the link above from my blackberry but it only shows 3 or 4 posts and one with images it says is not viewable?

I am aware this is a common problem, I searched CK5.com yesterday and mostly came up with the same info we already tried. Guess only left to do besides grounding the SU wire is to drop the tank and check the ground @ the SU and I guess pull the SU and check with an ohm meter?

[Got Smoke?]

Since you say it's up by the starter I assume this is a single right hand tank? Ground the sending unit wire key on engine off (KOEO) and see if the gauge reacts.

Grounded the wire coming from the gauge to the sending unit and the gauge needle went from 3 o'clock to E. I suppose this means my sending unit's trash?

Local auto parts all want $70 + tax for more...rockauto.com wants $50..didn't check what they charge for shipping though?

[VileZambonie]

If it went from left to left then I would check your gauge and your wiring

[Irish_Alley]

how does something go left to left vile 

[Got Smoke?]

It went from 3 o'clock past full to EMPTY when I grounded the wire coming from the gauge. So is it my sending unit or the gauge?

[VileZambonie]

If it went from full to empty check the sender. When you said 3 o'clock to empty I assumed you meant the needle is swinging 

[Got Smoke?]

If it went from full to empty check the sender. When you said 3 o'clock to empty I assumed you meant the needle is swinging  

No with the tank in the truck (and about a half tank of gas in it) the gauge was reading 3 o'clock position past full. When I grounded the wire coming from the gauge towards the sending unit to the frame it went from 3 o'clock to E.

Pulled the sending unit out of the tank and checked it with an ohm meeter. 1 all the way down and 100 all the way up...I know I know GM sending units are supposed to be 0-90 ohm's but its a cheapie of my fathers. So this means the sending unit is good correct? Should I start tracing the wiring from the start area back into the cab to the gauge?  Geesh....I'm lost on what to do guys? I keep searching here, CK5 but keep coming up with the same things I've already checked?

[VileZambonie]

OK if it ohm'd out ok and the connections are good check the wires going to the gauge. If they're not corroded or chafed check the gauge and the circuit board. My 85 does the same thing. If you tap on the gauge it'll read correctly. I have to fix mine as well.

[Got Smoke?]

Thank you I will check that next chance I get to work on the truck.