Replaced Fuel Sending Unit, Gauge Still Not Working!

gistecknician · #1 (**permalink**) 08-23-06, 09:21 PM

I started having problems with my fuel sending unit after a 1200 miles trip from New York to Florida in my 1992 Eldorado. The fuel gauge would do a full sweep to full, and then go back to empty and stay there.

After checking every single fuse in the vehicle and reading many threads with people that had the same problem on this site I concluded that the fuel sending unit must be bad. I ordered a new AC Delco fuel sending unit for $288 from Auto Parts Fast at RockAuto, let my car run until it died to expel all fuel in the tank (23 1/2 hours), and replaced the following:

Fuel Sending Unit
Fuel Pump
Fuel Screen
Fuel Filter

Guess what...the gauge is still not working! What could it be? Any suggestions would be greatly appreciated. By teh way, FedEx delivered teh Sending Unit in a pretty beat up box....should this has raised a red flag?

Krashed989 · #2 (**permalink**) 08-23-06, 09:39 PM

It could be one of three things:
1. Defective level sensor on the sending unit
2. open/shorted circuit between the level sensor and the cluster
3. Bad cluster.

The system basically works like an ohmmeter. The level sensor has a floater attached to a lever which is attached to a variable resistor. The cluster then reads the resistance given by the sensor and guages that to display the fuel level. If you find the wires and take a reading with an ohmeter, then fill the tank and take another reading with the ohmeter, you should get different results if it's working properly. If you get the same results both times (before and after filling the tank) then I would say that you need a new sending unit. Otherwise, you need to check the wiring to the cluster. If all the wiring is good also then it's the cluster.

gistecknician · #3 (**permalink**) 08-24-06, 09:42 PM

I will check the wiring to the cluster as well as the cluster itself, thanks for the reply.

I hope that it is not the brand new sending unit, as I would hate to have to drop the fuel tank again, it was very easy to do...but I just don't wanna do it again if I don't have to.