My fuel guage (analog) has started to jump around erratically. It's always been rock solid... sure it would move around a touch depending on whether I was going uphill, downhill, etc. but it wouldn't be noticable.

Now, it twitches -- sometimes by as much as a 1/4 tank fluctuation. It's pretty steady when idling... mostly moves when driving. It's actually mostly accurate, though. I'm sure it's showing the correct reading when it's steady.

Funny thing is that right before this tank of gas I was running on as empty a tank as I ever have. Didn't run out of gas, but thought I was close. I filled it up and then noticed this. Probably coincidence, but who knows.

Any ideas?

 

the "float" in the take for the variable resistor is acting up, or you have a short in the signal feed wire from the pump to the gauge...

 

Would that be kind of a funny deal with your friends in the car. Floor the car and the fuel gauge needle goes down by a 1/4 tank. I've had friends with old muscles cars that would do that.....but they really were down a quarter tank!

S

 

Shoot... so it sounds like it's not coincidence after all. Maybe taking the tank down to fumes the other day whacked out the float.

I'll also start tracing the sending wire to the gauge.

Thanks.

 

Try giving it a few fill ups first and see if it stabilizes too....it could be that it's just out of whack because you ran the car close to dry. If it doesn't help, then you gotta fix something.

S

 

Sarin's got a point...the float may be sticking, or something...a couple of fill-ups may clear it up...

 

My Nova SS gets about 8-10 MPG... but there is a 40 Ford
Tudor that runs a 502 BBC and a 68 Camaro that runs a blown
and injected 468 BBC... both of these cars you ask, "How many
gallons to the mile do you get?"!

Scott

 

you can also try disconnecting the sending unit wire at the fuel pump, and then driving and seeing if the problem continues, but really the only way to do that is to cut it. you can't disconnect the harness for the fuel pump because it wouldn't turn on, and the car won't run. according to the FSM for my 88 maxima, you should have these wires at the fuel pump connector:

Black is the ground.
Green/Yellow is the fuel gauge signal wire
Orange is the low fuel warning light signal wire

there will be 1 or 2 more for power.

if you haven't isolated it yet, disconnect that green/yellow wire, then turn the ignition on. the fuel gauge should drop below E. drive for a few miles, or until the problem normally starts. the gauge should stay below E still. if it's still jumpy, assume you have a short to ground somewhere between that connector and the fuel gauge. if the needle didn't move at all, assume you have a bad variable resistor in the sending unit. now with the ignition on, touch the green/yellow wire to ground. the gauge should shoot the whole way up to F.

if you'd like instructions for testing the sending unit, I can look it up.

Dan
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