I have a 86 IROC 305 carbed that I'm working on for my niece and the Fuel Gauge is erratic 90% of the time (it bounces everywhere) regardless of gas pedal/brakes/car movement. From what I have been reading on searches, everyone here seems to think it is the Fuel Sending Unit in the tank.

I also have an 88 IROC, L-98 TPI with a known good Sending Unit. Can I use this Fuel Sending Unit as a direct swap into the 86 or is it different? I know it's a pain to get too, but I'm already swapping the rearends and it would be the perfect time to tackle both jobs.

Also, where and how do you read the OHMs to verify it is the sending unit and not a bad gauge?

Thanks,
Magman

 

They should be a direct swap.

Also Summit sells some after market sending units but they will require some mods (easy ones).
http://store.summitracing.com/egnsea...115+4294776442

Once the sending unit is out out of the tank, (but the way the sending unit is part of an assembly including 4 fuel lines and the fuel pump), measure across the 2 wires on the POT, which is attached to the float.

You should change the fuel pump and filter before reinstalling or you'll hate yourself it goes out down the road and to remove the gas tank again.

 

OK, thanks. I'm not sure what youre speaking of regarding the "POT". I'll search some more and see if I can find a diagram since I'm not curently working on it. I thought there was a way to read out the wires at the connector in front of the gas tank for the 0-90 OHMS?

 

"POT" is the short form of Potentiometer, a Variable Resistor; similar to a dimmer switch for lack of better example anyway depending on the level of fuel in the tank it should read between 0-90Ωs.
Without pulling the sending unit out of the car you will only be able to read one value, hopefully somewhere between 0-90Ωs. You can do this by measuring the Resistance between the Violet wire and ground. At least that's the color on my car.
Even so it won't tell you much because you can't move the float inside the tank from empty to full and see how it acts during the full range of motion.

I hope this explanation helps.

 

Thanks man. I'm familiar with a potentiometer, learned all about it with my TPS! My guess is that I wouldn't read one value at the connector outside the tank, since the gauge is erratic the values should be fluctuating. We'll see... Thanks again for your help.