Narrative:

At 35 minutes into flight at cruise; fuel imbal light on right main tank illuminated. Verified cross feed valve was closed and main fuel pumps were on. Center tank fuel was 0.00. Started fuel leak- engine checklist in QRH. Suspected fuel leak and requested diversion to ZZZ which was nearest suitable airport. [Advised ATC] minimum fuel. Landed and contacted maintenance control. Maintenance determined cross feed valve malfunctioning. Aircraft was grounded.as an addition contract maintenance was instructed to stick the tanks which confirmed that there was a fuel imbalance but there were no other tests done as far as finding a leak or checking the fuel system. Maintenance stated to me that there was nothing else to test and they thought everything was fine and to take the plane to destination. I insisted on more investigation which revealed that the cross feed valve was allowing fuel to be transferred from the right tank to the left tank with the cross feed valve in the closed position. During this lengthy process the gate agents were pressing me to board the aircraft for departure. I stated that we were not finished with the testing and to hold off until I advise her. We came to find out that our maintenance personnel were making comments to the contract mechanic that 'the pilots don't want to fly today' and 'they wanted to come here'. Comments like that are very unprofessional and are not conducive to a safe operation. Contract maintenance confirmed that the cross feed valve was not functioning correctly and informed maintenance control.

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Original NASA ASRS Text

Title: B737 flight crew reports diverting for a possible fuel leak and a fuel imbalance.

Narrative: At 35 minutes into flight at cruise; fuel IMBAL light on right main tank illuminated. Verified cross feed valve was closed and main fuel pumps were on. Center tank fuel was 0.00. Started fuel leak- engine checklist in QRH. Suspected fuel leak and requested diversion to ZZZ which was nearest suitable airport. [Advised ATC] minimum fuel. Landed and contacted Maintenance Control. Maintenance determined cross feed valve malfunctioning. Aircraft was grounded.As an addition Contract Maintenance was instructed to stick the tanks which confirmed that there was a fuel imbalance but there were no other tests done as far as finding a leak or checking the fuel system. Maintenance stated to me that there was nothing else to test and they thought everything was fine and to take the plane to destination. I insisted on more investigation which revealed that the cross feed valve was allowing fuel to be transferred from the right tank to the left tank with the cross feed valve in the closed position. During this lengthy process the gate agents were pressing me to board the aircraft for departure. I stated that we were not finished with the testing and to hold off until I advise her. We came to find out that our Maintenance personnel were making comments to the Contract Mechanic that 'the pilots don't want to fly today' and 'they wanted to come here'. Comments like that are very unprofessional and are not conducive to a safe operation. Contract Maintenance confirmed that the cross feed valve was not functioning correctly and informed Maintenance Control.

Data retrieved from NASA's ASRS site 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.