Just did some work on my 86 fj, new brake pads and rotors upfront, and it had sat for about 2 weeks while I was working on the bike, Now when I turn it on the fuel light stays on, WHY??? And Yes it has gas!!
Fuel gauge working or just reading dead empty?
Checked wires from dash to sensor under the tank as best you can?
Checked fuses? I discovered the other day FJ's do crazy shit when a fuse goes.
Could be the sensor itself?
I do not know exactly how the FJ works but I know a corvettes very well, and I would assume they are close to the same idea. So on a vette the float moves a needle on a tightly wound wire and the gauge does a ohm reading of resistance between the needle connected to the float and the wire. On the vette if there is zero Ohms, broken wire, then it reads full but the FJ may be opposite. You can check the resistance on the two wires coming on the bottom of the tank. At that point you and decide if it is worth fixing or just read mileage instead...
If the circuit is open (unplugged, for example) it'll read hard empty. If it's directly shorted, it'll read full. If my memory isn't totally shot, at least.
Quote from: andyb on June 30, 2011, 11:18:19 PM
If the circuit is open (unplugged, for example) it'll read hard empty. If it's directly shorted, it'll read full. If my memory isn't totally shot, at least.
I agree with andyb
In my professional experience every fuel sender unit I've had to test have high resistance at the empty end of the gauge.
It's something of a fail safe so you don't think you have lots of fuel when you don't.
That's on japanese and aussie stuff anyway, couldn't comment about stuff from the USA as i've never worked on anything other than a clapped out jeep (shudder)
Kev
yup sounds like the connector is loose on the left hand side next to the battery .
mine was acting up a few years back and I just used some pliers to move the float up and down a few times and it has worked fine ever since.
Did you change any dash bulbs to LED? The fuel light will stay on (full bright) if changed to LED, it requires an electrical resistance and an LED is an open circuit. It will stay bright red all the time....