Streetgliderx
1/2 ton status
my gas guage cances when i move as if the float it movin to the sloshing gas. sittin still its still. what gives?
CK5
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gas guage dancing
- Thread starter Streetgliderx
- Start date
wannabehero
1/2 ton status
mine does too dont worry about it. everyone ive spoken to says its from the gas sloshin around and its typical of older trucks
Your gauge is bad.
The "resistance" to changing fuel levels (like after you fill up, turn the truck on, and the gauge *slowly* goes to full) is done through the gauge.
GM states in the gauge testing procedures that you need to wait up to a minute for the gauge reading to accurately reflect fuel level.
If the gauge fails, it simply reads the float level instantaneously, which as you are seeing, changes quite a bit, and fast.
The "resistance" to changing fuel levels (like after you fill up, turn the truck on, and the gauge *slowly* goes to full) is done through the gauge.
GM states in the gauge testing procedures that you need to wait up to a minute for the gauge reading to accurately reflect fuel level.
If the gauge fails, it simply reads the float level instantaneously, which as you are seeing, changes quite a bit, and fast.
Sooo, technically speaking, the gauge is bad, but still works?
Yeah, I'm not sure how the gauge "dampens" the reading from the sender, but that is one of it's functions. Seems odd that only that portion of it can quit working correctly to me, but without knowing how they work internally, I don't know why it happens.
My truck was doing that before I replaced the gauge (and I went through the sender as well, testing) and it read fine as long as I wasn't moving, or was cruising with no bumps. Since the dampening effect was gone, as soon as the fuel settles down, the reading is immediately accurate. Just annoying hitting speedbumps and the like.
My truck was doing that before I replaced the gauge (and I went through the sender as well, testing) and it read fine as long as I wasn't moving, or was cruising with no bumps. Since the dampening effect was gone, as soon as the fuel settles down, the reading is immediately accurate. Just annoying hitting speedbumps and the like.
ditto.
Streetgliderx
1/2 ton status
its not enough for me to start tearin dash out. but i know now when it stops dancing just before the E its time to fill cause there aint enough fuel to splash around
Mine is doing a different dance, the electrical sort. Even sitting still its flying all over the gauge face, I guess my sending unit is shot, anyone know what ohm these senders are, I may as well pick up an aftermarket gauge for the dash Im building too.
pvfjr
1/2 ton status
The short isn't necessarily in the sender. You might have a signal wire flirting with ground. When the wire grounds out, it goes to empty. Or, if the wire becomes disconnected from the sender, the guage goes up past full. From my experience, these two options are very common, and the senders are usually fine.
My gauge did weird things and the wire going back to the tank had gotten hot close to the header and had the old green copper going on, I spliced in a new section of wire and it has been fine for years with the only problem that it is off a quarter of a tank with the topper and tail gate off.
1978Blazerk5
1/2 ton status
my speedo doubles as a bump meter past 40 mph. Lol it will bonce everytime I hit a hard bump. I hit a bump so hard it bonce to 90, then to back to 30, then it went back to 50mph. lol
pvfjr
1/2 ton status
Your tank may not be grounded properly. Does it read a quarter tank high?
I dont understand the quarter tank high, but it is out of gas at a quarter of a tank mark on the gauge and full is way past full mark. I think its elevation, the rear lifts 1.5 inches without the top and tailgate.
I doubt it's elevation, likely you've got an issue with the fuel gauge circuit.
Mine does the same thing, (and my truck is very close to level) really haven't spent enough time tracking it down, but with two different senders/different grounds the gauge reacts the same way. E is about 1/8-1/4 tank, F is about 1/8-1/4 over as well.
Mine does the same thing, (and my truck is very close to level) really haven't spent enough time tracking it down, but with two different senders/different grounds the gauge reacts the same way. E is about 1/8-1/4 tank, F is about 1/8-1/4 over as well.
pvfjr
1/2 ton status
Meaning, the guage reads a quarter of a tank higher than what's in there. So, you tank is empty at 1/4 on the guage. That's what'll happen when there's a bad ground on your tank. Make a new ground wire and re-ground your tank, and I'll bet the accuracy will improve. The guage simply measures resistance through your sending unit to ground. At the factory, a small ground wire was clipped onto the top of the sending unit and run to the frame. They are little and weak, and susceptible to corrosion, and often break off. Then the tank is "kinda" grounded, through straps and whatnot. But there will be a small amount of resistance added into the path for your signal wire, usually about 15 ohms or so. You can test it by taking an ohmmeter to your tank. Measure from the tank body, to the frame of the truck. You *should* have 0 ohms, I'll bet that you don't.
pvfjr
1/2 ton status
You could have a bad connection, somewhere past the switch, if it applies to both tanks. Or the guage itself could actually be inaccurate, but I haven't seen that before. You can actually bench test the guage out of the truck. I have a cigarette outlet in my computer, and I usually use that to tinker around with 12v stuff inside the house. If you want to know how to check the guage, lemme know. But I wouldn't blame you if you just left it there. Usually takes me years to get around to that sort of thing.
Appreciate the offer! I'm thinking I may start a fuel gauge circuit diagnostic post, I've got some testing questions myself for the sender, since I could never get the resistance as my multimeter read it, to vary even close to 0-90 ohms, even though they work when connected to a gauge. Would appreciate your input if/when I start the thread.
I forgot about that little ground wire, I have to look while no guts are in the truck right now. Elevation thing is bad enough I have to adjust the headlights, although, cant wait until I have the mula and CanBack gets the soft tops made starting this month.
pvfjr
1/2 ton status
No problem, just hit me up whenever you get around to it. That's something I've always thought of doing, just never did. I have fixed a LOT of gas guages though, so I've got a bit of input to pass along. Looks like I'll be working on an '82 tomorrow, with one of the more complicated valve/switches. They were pretty simple back in the 70's when there was a one-wire solenoid valve, but you never knew for a fact that you were running off the tank that your guage indicated. I switched to the left tank once, the guage went up to full, then I ran out of gas cause the solenoid never got switched.
The guage was lying to me the whole time. Those 80's setups had the momentary switches at the dash, and the sending unit wires were actually switched at the valve, so no more false readings....supposedly.
viknguy
Registered Member
How hard is it to get to the ground wire on the tank
