Is my gas gauge working correctly??

[hotwls13]

I think it’s working, but thought it would read higher. My new to me 70 gmc lwb 1/2t 350/350 had a half done blazer rear tank swap when I got it. I think I have everything hooked up right etc. when I first got the truck when started I “think” I remember the gauge going way to the right. Found neither sender wire (ground or the brown wire) were hooked up. I hooked them up but only had like an inch of gas. At that point the gauge read a bit below E. Today I finall got time to get 5 gallons in it. Now it reads about 1/8?? Thought it would read more like 1/4 since I “think” it’s a 21 gallon tank.

Thoughts?

[dmjlambert]

I think it looks good. You'll have more information when you do a fill up. I bought a nice clean new wooden dowel from the lumber store to dip in the tank and see how much gas I had and compared the reading on that to the gas gauge. I did that for a while through the whole range of full to empty. Just to get a feel for the situation.

[hotwls13]

Originally Posted by dmjlambert

I think it looks good. You'll have more information when you do a fill up. I bought a nice clean new wooden dowel from the lumber store to dip in the tank and see how much gas I had and compared the reading on that to the gas gauge. I did that for a while through the whole range of full to empty. Just to get a feel for the situation.

Yeah truck is still kinda torn apart. Bed is off. I’d rather know the gauge is working before putting the bed back on. I’ll probably have to lug another 5gallon gas can (or two) to verify it’s going up properly. I think I had read where the “new” metal floats were filling with gas (causing low readings) and guys were replacing them with Jeep floats.

[Smitty]

Suggestion: Vent to both sides of the tank. The guy who installed mine just did the vent on the passenger side and it is a pain in the ___ to fill. Am having the vent hose added on the nipple on the drivers side as well. So it will vent faster when filling it up.

[dmjlambert]

Are you all using roll over valves?

[hotwls13]

Originally Posted by Smitty

Suggestion: Vent to both sides of the tank. The guy who installed mine just did the vent on the passenger side and it is a pain in the ___ to fill. Am having the vent hose added on the nipple on the drivers side as well. So it will vent faster when filling it up.

I’m planning on only doing the drivers side. The large 1/2” vent line right next to filler on the tank. Planning to run that up into fender.

[hotwls13]

Originally Posted by Smitty

Suggestion: Vent to both sides of the tank. The guy who installed mine just did the vent on the passenger side and it is a pain in the ___ to fill. Am having the vent hose added on the nipple on the drivers side as well. So it will vent faster when filling it up.

I'm not sure which are vents and which are supply lines on mine. I believe at least one of the small ones is for fuel injected engines. So the lines may go to bottom of tank instead of just venting at the top. Pretty sure the big one next to fill is main vent though.

[Grumpy old man]

this thread should help

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

[demian5]

You could pop for a new sender, and make sure all the grounds are good and clean.

[hotwls13]

Put another 4+ gallons in. It’s moving up so it’s working. Just not sure how accurate it is. I’d guess about 8 gallons in a 21 gallon tank.

[hotwls13]

Originally Posted by demian5

You could pop for a new sender, and make sure all the grounds are good and clean.

I grounded to the tank bolt that bolts tank to the frame. Looks like it’s moving so I’m guessing it is good. I’m gonna keep adding fuel as I can get to the gas station. Maybe have it full soon.

[demian5]

Originally Posted by hotwls13

I grounded to the tank bolt that bolts tank to the frame. Looks like it’s moving so I’m guessing it is good. I’m gonna keep adding fuel as I can get to the gas station. Maybe have it full soon.

Good ground at the cab to frame and cluster to cab?

[hotwls13]

Originally Posted by demian5

Good ground at the cab to frame and cluster to cab?

No idea if those grounds are good or not. Wouldn’t a bad ground just cause it not to work at all?? It’s working, it’s going up when I add gas. I just wasn’t sure if it’s eyeball accurate.

I’m done troubleshooting it for now (too many other things to do). Once it’s full if it’s not reading full, I’ll get back to testing things.

[Grumpy old man]

Ok , You know the gauge is moving when more fuel added raised the gauge level . just remove the tank pick up and straighten the float rod a bit to make the gauge move up ,you may have to adjust more than once to get it close , with a 21 gallon tank that you added 8 gallons to it should be just below 1/2 on the gauge. carry a small gas in back and drive the truck until it reads empty . the small can of gas is in case it runs out . don't chase electrical gremlins when a simple adjustment of the rod will do the trick !

[WorkinLonghorn]

Yep, that's the ticket right there ^. Listen to Grumpy.