Ford on October 19th, 2010 has issued TSB 10-21-3 (Technical Service Bulletin) for 2011 Mustang V6 and GT’s, with 3.7L and 5.0L engines.
Some 2011 Mustang V6 and GT vehicles may exhibit a fuel gauge indicator dropping from approximately 1/2 to 1/4 full to E, and Message Center displaying 0 Miles to Empty. This concern may be intermittent. Customers may also notice that when refueling, the vehicle takes only 7 to 10 gallons of fuel (tank capacity is 15 gallons).
The Mustang has a saddle type fuel tank in that there is a hump in the middle of the fuel tank for the driveshaft. There is one electric pump and fuel level sensor on the driver side of the fuel tank, this is the Fuel Pump Module. There is a fuel pick up and fuel level sensor on the passenger side of the fuel tank.
The system draws fuel first from the passenger side of the tank. The Fuel Pump Module siphons fuel from the passenger side of the tank via the fuel pick up. Once the fuel level on the passenger side is too low to siphon fuel, there are check valve that close and the fuel will now be drawn from the driver side of the tank via the Fuel Pump Module.
The fuel level senders read the fuel levels on both sides of the tank. The two values are averaged for display on the fuel gauge. The fuel gauge system will drop the fuel gauge indicator to E if it sees a large difference in the fuel levels from the driver side to the passenger side fuel level sensors. The system is expecting the passenger side of the tank to go down before the drivers side. Sending the fuel gauge indicator to E and having the message center low fuel warning turn on warns the customer that he may fun out of fuel.
TSB’s are covered under the New Vehicle Warranty, if you see evidence of this problem contact you Ford Service Center for more info.
Download the pdf here: Ford Mustang TSB 10-21-03