This was consistent until the problem occurred. Suddenly, the fuel gauge has become far less sensitive. The gauge now reads about full when there is 240 to 280 miles on the tank. When we fill the tank, it takes 12 to 14 gallons as it should, based on the mileage. The gauge rarely reads below half no matter what the mileage, though we never put even 300 miles on the tank.
I took the van for service at the GM dealer three different times. The first time they changed the “Fuel Level Sensor.” The second time they ran some diagnostics and indicated the sensor was performing to GM specifications. The third time they removed, tested, recalibrated and re-installed the sensor.
None of these procedures did anything to fix the problem. I was charged $300-plus for the first appointment and nothing for the next two. When I turn off the van, the gauge drops to zero as do all other gauges, so it does not appear to be a mechanical problem.
Do you have any suggestions as to what this could be?”
Halderman: This is a very common problem and it is caused by a poor ground connection.
Usually rust is the cause. Take the van to a shop and ask that the ground connection for the fuel gauge circuit be checked and repaired as needed. It is usually under the van near the rear where road salt can cause corrosion.
The high resistance caused by a poor electrical ground connection causes the gauge to read higher than normal.
I ran out of gasoline one time because of this fault. The gauge showed a full tank but I ran out of gas. Fixing the corroded ground connection restored proper operation of the gauge.
General Motors vehicles use a variable resistor attached to a float to sense fuel level.
• Low fuel level is a lower resistance
• High fuel level is a higher resistance
Therefore, when the resistance is increased in the fuel sensor circuit, the dash gauge reads the level indicated by the circuit resistance.
James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
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