Instruments - New Fuel Level Sensor Testing Caution

GROUP 16
Fuel Supply Systems

Bulletin Number
16 04 98

Woodcliff Lake, NJ
May 2000
Service Engineering

This Service Information bulletins supersedes S.I. 16 04 98 dated January 1999.

SUBJECT:
Fuel Level Sensor Gives False Resistance Readings

MODEL:
E31, E32, E34, E36 (including Z3), E38, E39, E46, E52, E53

Situation:
A fuel level sensor unit has open circuit, or high resistance when tested out of the vehicle.

Cause:

1. Replacement fuel level sensors are oiled to prevent contact corrosion. If a replacement fuel level sensor is tested prior to vehicle installation, dust particles which are attracted to the oiled surface, may falsely indicate an open circuit or high resistance condition, as the float arm is moved through its operating range.

2. When a multimeter on "Auto" range is used to test a fuel level sender's resistance, the multimeter momentarily shows an "out of range" display as the fuel sender's float arm is moved through its operating range. This is caused by the meter switching between ranges but can be misinterpreted as a momentary open circuit in the fuel level sensor.

Correction:

1. Clean the resistor card prior to testing a replacement fuel level sensor, using aerosol electrical contact cleaner. Allow the contact cleaner to evaporate, and then proceed with the test using a multimeter set on "Kohm" range.

2. Select a multimeter (for example Fluke 83) which can have the range manually set. Set the multimeter range to "Kohm", then slowly sweep the float arm through its full range of movement in both directions, at the same time observing the multimeter display.





General Information:
For information, fuel level sensor resistances are as shown.