Narrative:

Noticed fuel imbal of 1200 pounds between the left main and the right main tank 40 NM east of ZZZ. Open xfeed to correct fuel imbal. That seem to correct the fuel imbal. Over ZZZ check the fuel remaining, we had 8.5 and the flight plan said we should have 10.2. When we were about 40-50 NM west of ZZZ noticed that fob was 8.0 decreasing faster than normal. We checked fuel burned and fuel total remaining we were coming up 2000 pounds short. At this point we ran the communication procedure 2.28.9 fuel leak procedure. We thought it was more appropriate than the 2.28.14 because all fuel quantity indicators appeared normal. Call dispatch and explained the problem and told him I thought we should divert to ZZZ because our fob was indicating 6.8 and could not determine the source of the leak or fuel lost. Both fuel tanks left and right were indicating approximately the same quantity 3.4/3.6. We divert to ZZZ and landed with about 6.8 fob. We noticed that fuel total remained pretty constant while diverting to ZZZ. At the gate when shut the engines down fuel remaining was left main 3.2 and right main was 3.6. About 1 1/2 hour later, while waiting at the quantity in the right main was ready 4.180 and the left was 3.180 fob or total fob of 7.3, 500 pounds more than we landed with. But still could not account for the large difference in fuel. The longer I hung around ZZZ and talking to maintenance controller, I suspect that maybe the right fuel quantity indicator is erroneous. But at the time we diverted to ZZZ we thought we had a fuel leak. On aug/sun/04, call maintenance control, and was advised the right fuel quantity indicator was bad. Aug/wed/04, the right fuel quantity indicator was written up as erroneous, maintenance did a byte test on the digital indicators/check normal/replace right fuel quantity indicator at ZZZ.

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Original NASA ASRS Text

Title: A DC9-30 AT FL350 NOTED FUEL IMBAL OF 1200 LBS. ADVISED DISPATCH. DIVERTED DUE TO SUSPECTED FUEL LEAK. ON GND R TANK QUANTITY INCREASED.

Narrative: NOTICED FUEL IMBAL OF 1200 LBS BTWN THE L MAIN AND THE R MAIN TANK 40 NM E OF ZZZ. OPEN XFEED TO CORRECT FUEL IMBAL. THAT SEEM TO CORRECT THE FUEL IMBAL. OVER ZZZ CHK THE FUEL REMAINING, WE HAD 8.5 AND THE FLT PLAN SAID WE SHOULD HAVE 10.2. WHEN WE WERE ABOUT 40-50 NM W OF ZZZ NOTICED THAT FOB WAS 8.0 DECREASING FASTER THAN NORMAL. WE CHKED FUEL BURNED AND FUEL TOTAL REMAINING WE WERE COMING UP 2000 LBS SHORT. AT THIS POINT WE RAN THE COM PROC 2.28.9 FUEL LEAK PROC. WE THOUGHT IT WAS MORE APPROPRIATE THAN THE 2.28.14 BECAUSE ALL FUEL QUANTITY INDICATORS APPEARED NORMAL. CALL DISPATCH AND EXPLAINED THE PROB AND TOLD HIM I THOUGHT WE SHOULD DIVERT TO ZZZ BECAUSE OUR FOB WAS INDICATING 6.8 AND COULD NOT DETERMINE THE SOURCE OF THE LEAK OR FUEL LOST. BOTH FUEL TANKS L AND R WERE INDICATING APPROX THE SAME QUANTITY 3.4/3.6. WE DIVERT TO ZZZ AND LANDED WITH ABOUT 6.8 FOB. WE NOTICED THAT FUEL TOTAL REMAINED PRETTY CONSTANT WHILE DIVERTING TO ZZZ. AT THE GATE WHEN SHUT THE ENGS DOWN FUEL REMAINING WAS L MAIN 3.2 AND R MAIN WAS 3.6. ABOUT 1 1/2 HR LATER, WHILE WAITING AT THE QUANTITY IN THE R MAIN WAS READY 4.180 AND THE L WAS 3.180 FOB OR TOTAL FOB OF 7.3, 500 LBS MORE THAN WE LANDED WITH. BUT STILL COULD NOT ACCOUNT FOR THE LARGE DIFFERENCE IN FUEL. THE LONGER I HUNG AROUND ZZZ AND TALKING TO MAINT CTLR, I SUSPECT THAT MAYBE THE R FUEL QUANTITY INDICATOR IS ERRONEOUS. BUT AT THE TIME WE DIVERTED TO ZZZ WE THOUGHT WE HAD A FUEL LEAK. ON AUG/SUN/04, CALL MAINT CTL, AND WAS ADVISED THE R FUEL QUANTITY INDICATOR WAS BAD. AUG/WED/04, THE R FUEL QUANTITY INDICATOR WAS WRITTEN UP AS ERRONEOUS, MAINT DID A BYTE TEST ON THE DIGITAL INDICATORS/CHK NORMAL/REPLACE R FUEL QUANTITY INDICATOR AT ZZZ.

Data retrieved from NASA's ASRS site as of July 2007 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.