Hey i was searching on the board for a while about broken fuel gauges. I just had a question... i have an 84 Z28 and the fuel gauge is broken. How can i tell if its the gauge or sending unit? I took the gauge out yesterday to see if it was all connected. when you have the gauge out of the car should you be able to move the needle anywhere you want it and have it stay there or should it drop down to empty, cause mine just stays wherever i move it to. When i start my car the gauge will go all the way up to about a 12 or 1 o'clock position on the gauge and stay there, but when i turn the car off it slowly drops back down. is this a bad sending unit or the acutal gauge itself? thanks for any help!

 

Sounds like the sending unit.

Find the SU wire at the gas tank; with it disconnected the gauge should go all the way to full, with it shorted to ground it should go all the way to empty. If it does that, you need a sending unit.

 

How do i locate this wire and test it? Do i have to remove the tank or does it just unplug somewhere within reach? So if i disconnect it it should go to full and if i touch the wire to the chassis like a ground it should go to empty? and if this isnt the problem then may it be the gauges? also how hard is it to drop the tank and how much for a new SU? Would it be cheaper to go to a garage and just get the work done. I have just standard tools, wrenches, screwdrivers, impact wrench.... Can it be done with these and is it worth all the trouble or should i bring it somwhere? And roughly how much would it cost me to bring it to a garage to get done? thanks alot

 

I can't recall what color it is, gray maybe? It goes to the top of the tank. You might be able to get to it and disconnect it, I've never tried in one of these cars. Some cars you can, some it's impossible; seems like these might be doable.

A new SU is about $80-100. You would have to drop the tank to change that I'm sure. Probably not all the way out though, just low enough to get clearance to get it out and back in. There's no special tools required, just yerbasic sockets and stuff; except that a "gas tank socket" makes it alot faster to remove the nuts that hold the straps on.

 

hey, i had a question, i just filled my tank but not all the way, the pump didnt shut off and that was at 16 dollars and i was pretty low, but now when i shut the car off the gauge droped to 3/4 of a tank and stayed there till i put hte ignition in again and tunred then it went back to the 12 oclock position. you think it could be the gauge or will the sending unit read the right amount when its shut off? is that a possibility? also when a normal third gen without this prob is turned off does the fuel gauge drop to empty like all other cars or does it stay at the level? thanks alot.

 

There are several different systems for making a gas gauge...

The most popular way is to use a heating element inside the gauge. That makes the gauge VERY slow to respond, which can be a good thing; but it also makes it go to empty, slowly, when you turn off the ignition.

The gas gauges in these cars, and a fair number of other ones, use 2 coils; one that gets power whenever the ignition is on, and pulls the gauge toward zero; and one that is connected to the sender, which pulls the gauge upward. That makes it much faster to respond, which some people like better. That kind has no spring inside it, and consequently just drifts and goes wherever it feels like, when the power is turned off.