Hey what the size of the fuel tank in a 1989 IROC Z my gas gauge is acting up and im tying to figure my range based on avg. observed mileage which is 16.5-17 mpg when not playing with it LOL

 

If it was never swapped, 15.5 gal.

 

Call it 14-16 gallons and you're in the ballpark. To the best of my knowledge, all the tanks 82-92 are the same physical size. The internal pump, baffling, etc displace more fuel than a car with just a sending unit and pickup, so the published capacity varies. If you look up the replacement tanks on Rock Auto, they're all listed as 14 gallons.

Of course the correct answer is to fix your gas gauge. Chances are pretty good it's the sending unit in the tank, but you'll need to troubleshoot it.

 

Yea I know but money is an issue right now so this helps thanks for the reply😉👍

 

Sorry to hijack this thread, but it is relevant to my issue. I changed the fuel pump before I had ever started the car and may have a bad gauge or I have the float in the tank flipped the wrong way. What can I do to test the gauge to make sure it is not that before I do all of the work in taking the tank back out to fix this. I have it full of gas right now and the gauge doesn't seem to move much from where it is at. Reads between quarter and half tank on the gauge. It will not read higher than that, but may read lower. I would have to run it out of gas to make sure on that.

 

Very possible that the gauge is bad. It's common for the gauges to stop reading correctly.

 

Is there any test I can do to determine it is the gauge and not the float or sending unit?

 

I removed the gauge from the dash because mine was dancing all over the place and would show 1/4 when full. I plugged a meter into the jacks the gauge plugs into and went for a drive and monitored the voltage on the meter. Since the voltage wasn't dancing and remained fairly constant, I knew the gauge was bad.

 

Since you indicate the gauge won't read higher than 1/2, an easy way to see if the gauge is capable of reading higher is to simply disconnect the fuel pump/sending unit connector under the car. You don't need to drop the fuel tank as there's a connector through the floor pan by the tank. Once you disconnect that, turn the key to On and see if the gauge reads full - as it should.

The gauge reads by measuring resistance through the fuel float. High resistance (or open) makes the gauge read high/full and low resistance makes the gauge read low/empty.

 

Ok cool. Thanks for the information guys. I'm going out of town this weekend, but I have all of next week off and plan on working on the car. So I will be trying this stuff out to see what I find. Thanks again!