Fuel Level Sensor Diagnostic & Troubleshooting Guide

Notice: General Reference Only

This information is provided for general reference only and is not an exact or complete step-by-step installation guide. Every vehicle, tank setup, and installation situation is different. Customers must research their specific application, adapt to their unique circumstances, and use common sense and sound judgment to complete the installation safely. Additional steps, materials, or precautions beyond those described here may be necessary. If you are unsure how to proceed safely, seek assistance from a qualified installer before continuing.

Work safely around fuel. Disconnect the battery before working on the sensor or its wiring. Remove the sensor in a well-ventilated area, and keep sparks, flames and other ignition sources away from fuel and fuel vapors.

Ohm range	Boyd SKUs	Empty (float down)	Full (float up)
0-90	33001, 33020-9.5	0 ohms	90 ohms (85.5–94.5)
240-33	33025-x, 33002	240 ohms (228–252)	33 ohms (31.35–34.65)
75-10	33003	75 ohms (71.25–78.75)	10 ohms (9.5–10.5)
0-30	33006	0 ohms	30 ohms (28.5–31.5)

Step 1: Does the sensor read properly?

What to do: Check whether the sensor is giving a proper reading for the fuel level in the tank.

What you should see: A reading that matches the fuel in the tank.

If yes: The sensor is OK. Skip the bench test and go to Step 7 to investigate the other components.

If no: go to Step 2 to bench test the sensor. Do the same if you're not sure.

Step 2: Remove the sensor and disconnect all wiring

What to do: Remove the sensor from the tank and disconnect all wiring from it. Note the sensor's orientation as you remove it: the 5-bolt pattern isn't evenly spaced, so it only lines up with the tank's sensor flange one way. Every test from here on is a bench test with nothing connected to the sensor.

What you should see: The sensor out of the tank on your bench, with no wires attached to its terminals.

If yes: go to Step 3.

If no: Don't test it in the tank or with wiring attached. Remove it and disconnect all wiring, then return to Step 1.

Step 3: Is the float arm present?

What to do: Inspect the float. On a swing arm style sensor, check that the float arm and float are there. On a vertical style sensor, check that the float is there. Move the float through its full travel.

What you should see: The float (and float arm on a swing arm sensor) present and moving freely from the bottom to the top of its travel.

If yes: go to Step 4.

If no: Replace the sensor. Go to Step 6.

Step 4: Check ohms at full

What to do: Connect the ohmmeter between the signal terminal and the ground terminal. Raise the float all the way up (full).

What you should see: The full reading for your sensor's range, within ±5% (see the spec table above).

If yes: go to Step 5.

If no: Replace the sensor. Go to Step 6.

Step 5: Check ohms at empty

What to do: Keep the ohmmeter connected between the signal terminal and the ground terminal. Lower the float all the way down (empty).

What you should see: The empty reading for your sensor's range, within ±5%.

If yes: The sensor is OK. go to Step 7 to investigate the other components.

If no: Replace the sensor. Go to Step 6.

Step 6: Sensor failed the bench test: contact us

What to do: If the float or float arm is missing, or the full or empty reading is outside ±5%, the flow chart result is replace sensor. Contact us before you buy a replacement.

What you should see: A missing float or float arm, or a full or empty reading outside the ±5% window.

Next: Sensors are covered by a 1-year warranty. Send us the items in What to Send Us so we can review a warranty claim, and we'll let you know the next step.

Step 7: Does your gauge match the sensor's ohm range?

What to do: Confirm your gauge (or ECM input) uses the same ohm range as the sensor. Watch our Ohm Range Video.

What you should see: The gauge and the sensor are the same ohm range, for example a 0-90 ohm gauge with a 0-90 ohm sensor.

If yes: go to Step 8.

If no: The gauge and sensor must be the same ohm range. Change the gauge or the sensor so they match, then recheck the reading.

Step 8: Is the sensor ground good?

What to do: Check the ground. Vertical sender: the black wire. Swing arm sender: the small post off center on the top plate (if there's no post, the ground goes under the mounting hardware). Follow it to the chassis.

What you should see: The ground connected to clean, bare chassis metal, or directly to the battery or a bus bar, with a tight, clean connection.

If yes: go to Step 9.

If no: Find or create a quality ground on raw metal, or run it directly to the battery or a bus bar, then recheck the reading.

Step 9: Is the signal wire connected properly?

What to do: Check the signal wire. Vertical sender: the blue, red, pink or white wire. Swing arm sender: the small nut on the center post (don't loosen the large nut). Follow it to the sender terminal on your gauge or ECM.

What you should see: A signal wire running to the gauge/ECM sender terminal with as few connections as possible, and no loose or corroded connections. Connectors should be weatherproof or weather-resistant and sized correctly for the wire and attachment points.

If yes: The sensor, ground, signal wire and ohm range all check out. Contact us with the items in What to Send Us.

If no: Repair or remake the connection, then recheck the reading.

The sensor only fits one way.
The fuel level sensor's 5-bolt pattern isn't uniform (the holes aren't evenly spaced), so it only aligns to the tank's sensor flange in one position. Rotate the sensor until all five bolts align before installing it.

Protect the threads.
Aluminum threads cross-thread and gall easily. Start every plug and fitting by hand and never install them dry. Thread damage from dry-fitted plugs or hardware isn't covered under warranty.