Gas gauge problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jessechop · 05-02-2011, 01:20 PM

Gas gauge was on empty for some time now, just moving the truck in and out of the shop, around the yard etc. so it wasnt a big deal, I just figured it was empty. Well yesterday I figured I better dump some fuel in it. i put 5 gallons in and it gave me 1/8th of a tank. I disconnected the sending unit wire and the gauge seems to work fine. Ideas?

68gmsee · 05-02-2011, 01:58 PM

Could be that it may need more gas. If it was completely empty, it takes a few gals to move the float from the bottom.

The float does not rest on the very bottom and by the time the fluid reaches it you'll have a few gallons on the bottom and your gas gauge won't show the whole amount. As you know, on most cars and trucks when the gauge reaches empty you still have some fuel to go farther.

Jessechop · 05-02-2011, 02:13 PM

Quote:

Originally Posted by 68gmsee

Could be that it may need more gas. If it was completely empty, it takes a few gals to move the float from the bottom.

The float does not rest on the very bottom and by the time the fluid reaches it you'll have a few gallons on the bottom and your gas gauge won't show the whole amount. As you know, on most cars and trucks when the gauge reaches empty you still have some fuel to go farther.

I actually thought about that. These trucks have a 20 gallon tank, I think? I just figured it would of been closer to quarter, but again I dont know how much was in it either

68gmsee · 05-02-2011, 04:17 PM

I've had mine down to empty in the past and never been able to put 20 gallons in it. The gauge is just a "ballpark" type of gauge. They're not super accurate and 1/2 tank may not mean you have exactly 10 gallons in it. You could have 11 to 12 left in there.

The best way to tell if the sending unit/gauge are working fairly close as a unit is to fill the tank up and see if the gauge goes all the way to full when the pump clicks off. Don't overfill it and make sure you don't park at a slant with the drivers side lower than the passenger side otherwise it may seep out of the fill tube.

Dark Knight · 05-02-2011, 07:37 PM

According to my owner's manual, the stock in-cab tank holds 18.5 gallons. My truck usually takes 15-16 gallons when the gauge is on 1/8 of a tank.

cparman · 05-02-2011, 07:46 PM

disconnect the sending unit wire, connect a test light to it, and look carefully. You should see a pulsing dim light. If you do the wiring and gauge should be good. The float could be full of gas, and reading empty all of the time. The brass floats had ends soldered on them, and will leak fuel into them. If the tank is really empty, remove the sender and then remove the float from the hanger and shake it. If you feel something in it, there is your problem.
Chip

**70STOVEBOLT** · 05-13-2011, 12:50 PM

I have the opposite problem, sort of. My gauge always worked correctly until recently, I noticed when i fill it up the gauge goes WAY past full. What would cause this?

dmack91 · 05-13-2011, 04:53 PM

Quote:

Originally Posted by 70STOVEBOLT

I have the opposite problem, sort of. My gauge always worked correctly until recently, I noticed when i fill it up the gauge goes WAY past full. What would cause this?

Probably the sending unit. If you ground the sending unit wire, it should go back to empty, if memory serves. That would eliminate the gauge as the problem.

Mine was the same issue. Sending unit was bad. And by bad, I don't just mean it wasn't working - the PO had cobbled together a "universal" one with a bunch of hose clamps, a coat hanger, and rubber line.

Cheapest replacement I found was Classic Chevy - $30, where LMC was 50.

pritch · 05-13-2011, 10:16 PM

Quote:

Originally Posted by 70STOVEBOLT

I have the opposite problem, sort of. My gauge always worked correctly until recently, I noticed when i fill it up the gauge goes WAY past full. What would cause this?

That's what mine does on my new '68. It's slowly working it's way up the list of Things To Fix Next

wh1skea · 05-13-2011, 10:44 PM

Today, the fuel gauge on my 68 seemed to quit working. when I parked it yesterday, it was at 1/2 tank. Got in it today and it was reading 1/8 tank. Went and put gas in it, cause I figured someone siphoned my tank (also bought a locking cap), but now its reading dead empty.

dmack91 · 05-13-2011, 11:28 PM

Make sure the wire is good from the sending unit to the fuse block, and that it is connected. Tank ground should be good too.

Sender should read between 0 and 90 ohms if good.

68 IRON · 05-14-2011, 04:27 PM

I personally don't like the locking caps. If someone wants the gas, they're alreading prowling around with tools to rip or pry open hatches, caps or what ever. This tells me if they do that to a Chevy gas cap that locks....the tank neck could get buggered up also.

05-02-2011, 01:20 PM	#1
Jessechop Registered User Join Date: Sep 2003 Location: maine Posts: 191	Gas gauge problems Gas gauge was on empty for some time now, just moving the truck in and out of the shop, around the yard etc. so it wasnt a big deal, I just figured it was empty. Well yesterday I figured I better dump some fuel in it. i put 5 gallons in and it gave me 1/8th of a tank. I disconnected the sending unit wire and the gauge seems to work fine. Ideas?

05-02-2011, 01:58 PM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Gas gauge problems Could be that it may need more gas. If it was completely empty, it takes a few gals to move the float from the bottom. The float does not rest on the very bottom and by the time the fluid reaches it you'll have a few gallons on the bottom and your gas gauge won't show the whole amount. As you know, on most cars and trucks when the gauge reaches empty you still have some fuel to go farther.

05-02-2011, 04:17 PM	#4
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Gas gauge problems I've had mine down to empty in the past and never been able to put 20 gallons in it. The gauge is just a "ballpark" type of gauge. They're not super accurate and 1/2 tank may not mean you have exactly 10 gallons in it. You could have 11 to 12 left in there. The best way to tell if the sending unit/gauge are working fairly close as a unit is to fill the tank up and see if the gauge goes all the way to full when the pump clicks off. Don't overfill it and make sure you don't park at a slant with the drivers side lower than the passenger side otherwise it may seep out of the fill tube.

05-02-2011, 07:37 PM	#5
Dark Knight Registered User Join Date: Dec 2008 Location: Pleak, Texas Posts: 420	Re: Gas gauge problems According to my owner's manual, the stock in-cab tank holds 18.5 gallons. My truck usually takes 15-16 gallons when the gauge is on 1/8 of a tank. __________________ -1967 Chevrolet Fleetside LWB- 350 V8 w/thumpr cam, NV3500, 3.08 gears, A/C, PS -1983 Chevy Silverado C1500- 383 stroker, TH400 -1989 Chevy Silverado K1500 SWB- 5.3L swap, 700R4, 3.42 gears -And a '66 Ford Mustang- 200 I6, C4 trans, rust bucket "The only thing we have to fear is fear itself." -FDR (and maybe rust too) You've gotta be able to stop and steer before you can go fast!

05-02-2011, 07:46 PM	#6
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: Gas gauge problems disconnect the sending unit wire, connect a test light to it, and look carefully. You should see a pulsing dim light. If you do the wiring and gauge should be good. The float could be full of gas, and reading empty all of the time. The brass floats had ends soldered on them, and will leak fuel into them. If the tank is really empty, remove the sender and then remove the float from the hanger and shake it. If you feel something in it, there is your problem. Chip

05-13-2011, 12:50 PM	#7
70STOVEBOLT Senior Member Join Date: Jun 2005 Location: Winona Lake, IN Posts: 6,266	Re: Gas gauge problems I have the opposite problem, sort of. My gauge always worked correctly until recently, I noticed when i fill it up the gauge goes WAY past full. What would cause this? __________________ 70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Power windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear

05-13-2011, 10:44 PM	#10
wh1skea Registered User Join Date: May 2011 Location: Chattanooga, TN Posts: 53	Re: Gas gauge problems Today, the fuel gauge on my 68 seemed to quit working. when I parked it yesterday, it was at 1/2 tank. Got in it today and it was reading 1/8 tank. Went and put gas in it, cause I figured someone siphoned my tank (also bought a locking cap), but now its reading dead empty.

05-13-2011, 11:28 PM	#11
dmack91 Registered User Join Date: Jan 2011 Location: Redmond, OR Posts: 758	Re: Gas gauge problems Make sure the wire is good from the sending unit to the fuse block, and that it is connected. Tank ground should be good too. Sender should read between 0 and 90 ohms if good. __________________ 68 Chev C20- son has it now 83 K20 - bought from son 70 C20 - in progress

05-14-2011, 04:27 PM	#12
68 IRON Registered User Join Date: Sep 2010 Location: Olympia, WA Posts: 736	Re: Gas gauge problems I personally don't like the locking caps. If someone wants the gas, they're alreading prowling around with tools to rip or pry open hatches, caps or what ever. This tells me if they do that to a Chevy gas cap that locks....the tank neck could get buggered up also.



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