Fuel Gauge jumps when RPMs move: Video added

[motorsports_3]

Unplugging the 3 pin one does nothing but when I jiggle it, I could see the gauge move a bit. Unplugging the 2 pin one shuts the gauge off. It falls from 3/4 to off.


It seems to be an electric issue. As I rev it up it dies. The guage didn't work when I first turned on the car, then I turned on the a/c and started working.

[Jean]

You may have a problem at plugs/pig tails, at the one with 3 pins. Because the 2pin and the 3pin ones are wired in series with each other unplugging either one should "open" the circuit OR in this particular case cause the gauge to drop. Since it's not doing that on one side, that's where I would check the wiring and/or cut that pig tail off and put another one (you can cut one wire at a time and see if the gauge drops as part of troubleshooting).

Get the ETM for your car.

[motorsports_3]

Okay, ill try that.

But if the pig tail is bad, wouldnt it cause the gauge to drop even if connected?


On another note, it seems that it may have something to do with volts. Since I dont remember if it was operational the last time I drove the car, before the motor swap, im thinking could it possibly be the alternator causing voltage fluctuations?

I find it hard to believe I was driving it with a bad fuel gauge before. And as you could tell in the videos it seems to be related to the revving. Earlier I turned the car on and the gauge didnt work, I then turned on the A/C and it worked as it has been doing.

[Jean]

Okay, ill try that.

But if the pig tail is bad, wouldnt it cause the gauge to drop even if connected?

Not if it's shorting, thats what you need to rule out.

[motorsports_3]

Cutting the wires did nothing.

Am I missing a ground somewhere? Is this setup grounded at a particular spot?

[motorsports_3]

Looking at the ETM, it gets wired into the OBC. I had changed to a 13 button, could that be a possible issue?

[motorsports_3]

Do you think that since I replaced the cluster with one from a eta, which would be 84-87 and mine is an 88 super ETA, that could be the issue.

The early ones used only one sender I think.

This thread brought the idea to my head.

http://www.r3vlimited.com/board/showthread.php?t=221618&highlight=fuel

[motorsports_3]

No one?

[motorsports_3]

What if the coding plug is different from the OBC and the cluster? What issue would that cause?

[motorsports_3]

So I have changed the cluster and the coding plug on the obc to a matching one and still nothing. Does anyone have an idea. This is really starting to blow my mind.

[motorsports_3]

It ended up being the round fuel level sender. I had replaced that one with a new unit, a few years ago, but I guess it went bad. Thanks for the help.

[Jean]

Nice! :)

The sender on the passenger side is 2 pin, it's like a variable resistor... The sender on the driver side is just like the one on the passenger side PLUS it's got an on/off switch for the low fuel light. The two senders are wired in series with each other, so if one is bad or faulty it will effect the overall result. BOTH have to be in working condition.