Hey guys....I have a little problem with my truck and hopefully you can help. A little background info....my uncle let me use his 1975 Chevy C10 since I lost my job and couldnt keep my previous car. So I needed something to get around in. He bought the truck for 500 bucks. So its not in perfect shape. Anyways, the gas gauge does not work properly and I just want to find out what is causing it and how to fix it. He bought he truck to use for something but it didnt work out. So he bought another and let me use the Chevy. He had it parked at my grandmas house for about a month and a half..to the middle of July. When it was decided I would use it...I picked it up and drove it to my moms house to park there since it was not under my name yet. My uncle said he thought it was low on gas, so on the way to my moms house we stopped and put $20 in it. The gas gauge went all the way past F. Parked it at my moms, dont remember where the needle was at when I turned it off. The truck was parked there for another month or so until a few days ago I got the truck in my name and took it to my house. While it was parked at her house it was never driven. We just started it up a few times while fixing some minor issues. SO today I came over to her house to visit and noticed the gas gauge is at the line right past 1/2 tank towards F. When I turn the truck off. The needle stays at the same spot. So if all of this made any sense....do you guys have any ideas on what to check or how to fix?
Check tank ground and guage wire connections at the tank. This is not an unusual problem with older trucks. I've had three of them.
I was thinking something with the wiring too. Are your gauges stock or are they aftermarket.
does it have dual tanks?????/ which fuel valve does it have ???? a 3 port valve or a 6 port valve..3 port valves have the tank sending units switched back and forth at the back of the switch..6 port valves have the switch built into the 6 port valve... i agree with dave... start with the grounds between the frame and the tank... the wiring to the back of the truck on that model.. i seem to recall comes out the firewall... through a round rubber grommet.. with a flat ribbon cable.. the tan wire from the tanks is the sending unit wire... you should be able to set an ohm meter to 200 ohm scale and read between the tan wire and ground some where between 10 and 90 ohms.. if you giggle the truck with your ohm meter attached.. you will be able to see the fuel sloshing in the meter readings.. ohm meters are fast to respond.. gas gauges are slow to respond.. stops them from wearing out do to constant swinging.. the tank wire also goes into the back of the cluster... you can measure it there also... should read the same as what you had at the tank... there is a tan wire that runs forward... to the high beams... but i hope you can see that they go different directions..
On my 76 GMC the first 1/8 of needle movement equaled about 1/2 tank. The calibration sucked for those 70's trucks.