Help!!!!!! Has anyone ran into this problem??? My gas gauge only shows full when running and at 1/2 full it is totaly out of gas it . With the ignition off it returns to empty. The truck has been converted to 12-volt. Should I buy a gauge, float or both? With the price of gas inquiring minds want to know.
Check the ground at both the guage and at the tank. Also, pull out the sender and make shure the rod to the float isn't bent so that it doesn't read the levels correctly. Also make shure the resistor is right for the 6v guage. If none of this works, start by replacing the sender. Truck shop has a great 12 v guage for cheap.
Fuel Gauge Testing You've gotta do it by the numbers else you'll chase your tail forever..... Take a jumper wire and connect it to a shiny part of the dashboard , clip the far end of it to the sener wire at the sender , turn on the key , this should drive the gauge to empty . if not , there's either a ground problem at the gauge (typically there's missing nuts & star washers holding the gauge head to the dashboard) or the gauge head is bad . Once you've ascertained the gauge head is good , then you can try messing with the sender , remove it and leave the two wires connected , turn on the key and move the float from one extreme to the other , watch the gauge ~ it should go from full to empty , if it only uses 1/2 the gauge's travel , you have the wrong impedance sender .
Thanks Guys! I bet is is a bad ground cause sometimes it goes to empty while the ignition is on. Is the impedence sender in the float?
Fuel Gauge Sender Impedance No ; it's built into the windings in the top of the sender assembly , the float just sits on the end of the movable arm . BTW : if you should happen to have a good metal float off the old dead sender , use that ~ the new synthetic floats occasionally get saturated with fuel and thence sink just enough to make the gauge read wrong... Taking the various hardwares apart and wire brushing is always helpful as is adding a bit of Moly grease to the contact surfaces of each connection ~ NEVER use dialectric grease ! . I like to add a brass or stainless steel screw to the sender for adding a ground wire that follows the harness all the way up to the dahsboard.... Just replace one of those Clutch Head screws holding the sender into the fuel tank . There's a push fit connector underneath the cab , it occasionally gets corroded or loose , clean and grease it or better yet , run a new two wire sub harness from the gauge head to the fuel tank for maximum accuracy . There are differing impedance senders used over the years in GM trucks ~ I forget the year model break but some are 0 ~ 30 Ohms and others are 30 ~ 90 Ohms IIRC , I know someone posted the details in the past so if you look in the archives under ' fuel gauge ' or ' gauge ' you'll find it but FIRST , do the basics so you know the gauge head is working properly....
Like Nate said, try the grounds first. After painting my truck and remounting, i found that the paint was so good that nothing was grounded properly. I assume your truck runs when the guage goes to empty? if not, then the ignition switch could be going on and off.
Actually , upon re - reading his last post , he says it occasionally goes to empty whilst driving ~ if it drifts slowly to empty , this indicates a lack of power wheras if it moves rapily to empty , this would indicate the sender wire has a bare spot on it and is grounding out intermittantly.... I hope the firewal grommet was replaced when the harness was out as that's the only time it can be done ~ you must not slit it to facilitate installation ! .
