Narrative:

In cruise at FL360 east of abc VOR; we received a 'fuel configuration' EICAS message some time after turning off the center tank fuel pumps with 1;000 pounds remaining in the center tank. We ran the fuel configuration irregular checklist. We confirmed the fuel crossfeed switch and closed and compared the totalizer and calculated values; confirming they were very close in value. We disconnected the autopilot and noted the airplane was left wing heavy and needed extra units of right rudder trim. We called dispatch and maintenance and the connection was less than good. Dispatch and maintenance could hear us but we could only hear dispatch; not maintenance. So dispatch was the relay between us. Talked about a possible fuel quantity indicator problem and to monitor it and call back if the situation got worse. They logged the item with these details: fuel calculation = 27.0; totalizer = 26.0; and the overhead fuel quantity indicators read: left = 14.4; center = 1.0; right = 10.9 and the fuel flows matched at 3.5. The problem did get worse as the right quantity was decreasing at twice the rate indicated by the fuel flow of 3.5. We timed it several minutes to confirm. We called again with the same bad communication connection between maintenance and us; using dispatch as the relay again. We had run the fuel leak irregular checklist noting that the totalizer and calculated fuel values were agreeing closely with the 'flight plan fuel.' maintenance was now talking about a possible fuel leak and we all agreed to make a diversion into ZZZ which was out in front of us about 35 minutes away. We declared an emergency in case we did have a fuel leak and headed for ZZZ. As we began our descent; we received several messages from maintenance; one of which asked us if the crossfeed switch was closed and if we had cycled the crossfeed valve switch. We then cycled the crossfeed valve switch and soon after we noted the left and right fuel quantity indicator values start to decrease at a rate comparable to the fuel flows. In other words we stopped seeing the right side decreasing as fast as it had been. The only message on EICAS for the recall/cancel part of the approach descent checklist was the 'fuel configuration' and nothing involving the relationship between the crossfeed valve and switch position; if there was a problem with the valve. The approach and landing were uneventful and taxi to the gate was also normal with the emergency equipment following us. After engine shutdown at the gate; we noted the fuel values: totalizer = 19.8; calculated = 19.8; fuel used = 33.2; the overhead indicators were: left = 12.7; center = .9; right = 6.1. We briefed maintenance with our details and proceeded to the new gate to fly to ZZZ1 with a new aircraft. Callback conversation with reporter revealed the following information: reporter stated the right drip stick reading he requested demonstrated that the right tank fuel quantity gauge was in fact reading correctly; not 1;600 pounds less as the MEL deferral stated. The initial log write-up noted a fuel imbalance had developed between the left and right tanks. Reporter stated since the right tank drip stick reading and quantity gauge were in agreement; the deferral for the right quantity gauge was not correct. The real issue was an uncommanded fuel transfer or fuel leak inflight of approximately 1;600 pounds. Maintenance supervisor refused to correct the MEL deferral; even though his line mechanics were telling him the incorrect deferral would make flight crews believe they have 1;600 pounds more fuel than what the quantity gauge read. The next outbound crew refused the same aircraft for the same reason. Reporter stated if a drip stick reading had been performed initially; the uncommanded fuel transfer or leak would have been realized and would not have been deferrable.

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Original NASA ASRS Text

Title: A B757 fuel crossfeed valve malfunction permitted the right fuel tank pumps to feed both engines after the crossfeed valve was closed because center tank fuel usage was ceased. A fuel imbalance resulted. An emergency diversion was made to nearby airport.

Narrative: In cruise at FL360 east of ABC VOR; we received a 'FUEL CONFIG' EICAS message some time after turning off the center tank fuel pumps with 1;000 LBS remaining in the center tank. We ran the fuel configuration irregular checklist. We confirmed the fuel crossfeed switch and closed and compared the totalizer and calculated values; confirming they were very close in value. We disconnected the autopilot and noted the airplane was left wing heavy and needed extra units of right rudder trim. We called dispatch and maintenance and the connection was less than good. Dispatch and maintenance could hear us but we could only hear dispatch; not maintenance. So dispatch was the relay between us. Talked about a possible fuel quantity indicator problem and to monitor it and call back if the situation got worse. They logged the item with these details: fuel calculation = 27.0; totalizer = 26.0; and the overhead fuel quantity indicators read: left = 14.4; center = 1.0; right = 10.9 and the fuel flows matched at 3.5. The problem did get worse as the right quantity was decreasing at twice the rate indicated by the fuel flow of 3.5. We timed it several minutes to confirm. We called again with the same bad communication connection between maintenance and us; using dispatch as the relay again. We had run the fuel leak irregular checklist noting that the totalizer and calculated fuel values were agreeing closely with the 'flight plan fuel.' Maintenance was now talking about a possible fuel leak and we all agreed to make a diversion into ZZZ which was out in front of us about 35 minutes away. We declared an emergency in case we did have a fuel leak and headed for ZZZ. As we began our descent; we received several messages from maintenance; one of which asked us if the crossfeed switch was closed and if we had cycled the crossfeed valve switch. We then cycled the crossfeed valve switch and soon after we noted the left and right fuel quantity indicator values start to decrease at a rate comparable to the fuel flows. In other words we stopped seeing the right side decreasing as fast as it had been. The only message on EICAS for the recall/cancel part of the approach descent checklist was the 'fuel configuration' and nothing involving the relationship between the crossfeed valve and switch position; if there was a problem with the valve. The approach and landing were uneventful and taxi to the gate was also normal with the emergency equipment following us. After engine shutdown at the gate; we noted the fuel values: totalizer = 19.8; calculated = 19.8; fuel used = 33.2; the overhead indicators were: left = 12.7; center = .9; right = 6.1. We briefed Maintenance with our details and proceeded to the new gate to fly to ZZZ1 with a new aircraft. Callback conversation with Reporter revealed the following information: Reporter stated the right drip stick reading he requested demonstrated that the right tank fuel quantity gauge was in fact reading correctly; not 1;600 LBS less as the MEL deferral stated. The initial log write-up noted a fuel imbalance had developed between the left and right tanks. Reporter stated since the right tank drip stick reading and quantity gauge were in agreement; the deferral for the right quantity gauge was not correct. The real issue was an uncommanded fuel transfer or fuel leak inflight of approximately 1;600 LBS. Maintenance Supervisor refused to correct the MEL deferral; even though his Line Mechanics were telling him the incorrect deferral would make flight crews believe they have 1;600 LBS more fuel than what the quantity gauge read. The next outbound crew refused the same aircraft for the same reason. Reporter stated if a drip stick reading had been performed initially; the uncommanded fuel transfer or leak would have been realized and would not have been deferrable.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.