Fuel Sending Unit Questions and Troubleshooting Information

A fuel sending unit measures the fuel in the gas tank by measuring ohm resistance by way of a rheostat connected to a float and lever. This is connected to a gauge located on the tank or in the cabin of the vehicle.

When purchasing a fuel sending unit you must match it up to the gauges in the vehicle or aftermarket company specs. The Ohm rating is the resistance rating used to identify what gauge goes with which fuel level sensor. Below is a list of applications for gauge and sender compatibility.

• Ford up to 1986 - 73-10 Ohms
• Ford 1987 & up - 16-158 Ohms
• GM up to 1964 - 0-30 Ohms
• GM 1965-1997 - 0-90 Ohms
• GM 1998 & up - 40-250 Ohms
• Mopar up to 1986 - 73-10 Ohms
• AMC 1950-1977 - 73-10 Ohms
• Autometer -240-33 Ohms is the most common however other ohm ranges are made
• Classic Instruments - 240-33 Ohms (excluding vehicle specific gauge kits which use factory ohm range)
• Dolphin - 0-90 Ohms
• Dakota Digital - Programmable to work with most Ohm range senders
• VDO - 10-180 Ohms

The first number represents the empty Ohm reading and the second number is the full reading.

FAQ

I Bought a new sender but my gauge only reads empty:

Depending on the ohm range you are running it could be the following problems.

1) For 0-30 and 10-180 Ohm Fuel senders - the ground wire is grounding out on the body of the vehicle or the terminal of the sender itself. 

2)For 240-33 or 73-10 ohm Fuel senders most likely the lead wire is grounding out somewhere. or the enter terminal on the fuel sender itself is grounding out against the body of the car.

I Bought a new sender but my gauge only reads Full:

Depending on the ohm range you are running it could be the following problems.

1) For 0-30 and 10-180 Ohm Fuel senders you may not have a proper ground or the lead wire is grounding out on the body of the car or there is a break in the lead wire.

2) For 240-33 or 73-10 Ohm Fuel senders - the ground wire is grounding out on the body of the vehicle or the terminal of the sender itself. 

Fuel Sending Unit Bolt Pattern = SAE 5 Hole 

The holes on the sending unit are the standard SAE 5 hole type. However the 5 holes are not evenly spaced effectively causing the fuel level sensor install only 1 way. 

Will The Fuel Sending Unit work with 6 or 24 volt systems? 

Yes, Fuel level sensors only measure resistance to ground, so they can be used with 6, 12, and 24 volt systems.

How can i test my fuel sending unit to see if it is working?

If you have a multimeter; set the meter to ohm Ω function on the multimeter and put the red test probe on the post that the gauge hooks to, and put the black probe on the ground post or body of the fuel lever lender. Move the float up and down from empty to full and record the readings on each end. This will tell you its working and will tell you the ohm range your sender is working at.

My Gauge Reads Backwards!

1)First thing to find out is if you have the proper fuel sender for the gauges you are using.

2) Second is make sure the float swing arm and float are coming out the correct side of the rheostat, it may be swinging the arm backwards and sending the opposite readings. also make sure the Rheostat is installed right side up. 

I took My Fuel Level Sensor Apart And Now It Does Not Work! 

1. Make sure that the main down bracket is in full contact with the flange at the top. There should be full continuity between the metal strip between the rheostat and the bracket and the bracket and the flange.
2. Make sure that the gauge lead post in the center is isolated from the flange and bracket. If the center post is grounding out it will only read zero ohms on a gauge or multimeter.