The fuel gauge on my 87 4runner is acting strange. Between full and 3/4 it acts normally. Anything below 3/4 though, it has a tendency to swing violently between full and empty. You can hear the needle slap the limits of its range. The slapping generally happens over bumps, turns and the like; anything to make the gas slosh around in the tank. So I figured this is a bad sender, since it seems to be the fuel moving around that causes it. I have a replacement sender, just waiting for an empty tank and decent weather to lower the tank and swap them. (which from posts here seems to be the way to change a sender) However, before I can do that (it could be a couple of months) I am getting concerned that the gauge needle slapping the ends of its range can't be good. And I am also wondering if something else is wrong here. Aren't gas gauges supposed to average their reading, so that every little bump and turn doesn't cause the needle to react immediately in a big way? Could there be something else amiss in this circuit so that each bump and turn is causing this extreme travel in the gauge needle? TIA

 

theres supposed to be some sort of fluid inside the guage that keeps it from sloshing like you said, normally its suppose to take about 30 sec to go from E to F when you fill up and if it takes over 90 it needs replaced so im guessing if it jumps quick then the fluid might not be in there?? good time to swap to SR5 cluster if you dont have one

 

No fluid in there now, just air. Hmmm, maybe I need a new gauge cluster not a sender...

 

The float in the gas tank works on a swing arm that raises and lowers resistance against what looks like a coil winding. Apparently if a wire breaks then the gas gauge works fine until it hits the break. If you're break is at 3/4 of a tank then as the gas sloshes around it's probably hovering around that broken wire.

That's my guess.

I just read someone else's writing about this recently, I haven't experienced it myself. I did just change my gas tank though and I checked it for wear before using it again. Mine was fine.

 

Yeah, probably worth trying the float assembly first; especially since I already have a good replacement.

What I was hoping to do is unplug the current float, just to keep the gauge needle from damaging itself. The replacement one I have (from a PU not a runner) has about a 10" lead on the top which goes to a plastic connector. I thought I'd be able to find that connector and unplug it, but I could not find it in looking around underneath. Is it tied up above the tank, or does it go thru the floor somewhere that one can access it from inside? Anyone know?

 

Don't know about the connector, but my '88 Pickup did this same thing. Gauge worked fine until about 3/4 and then would just drop to E and stay there. I had to use the mileage as a guide for how full/empty my tank was. I wrecked the truck before I could fix it.