What was found
ABOUT 4 MINUTES AFTER TAKEOFF, THE LEFT FUEL TANK SHOWED AN IMBALANCE WITH APPROXIMATELY 400 LBS DIFFERENCE BETWEEN LT & RT MAIN TANKS. COMBINED TO 1000 DIFFERENCE. THE AIRCRAFT WAS GROUNDED. PERFORMED QRH PROCEDURES. RIGHT TO LEFT, NO SIGNIFICANT FUEL FLOW DIFF. ACCOMPLISHED FUEL QTY BITE IAW FIM 28-41-00-810. NO CURRENT OR IN FLIGHT FAULTS. VERIFIED FUEL QTY USING STICK METHOD IAW FUELING MANUAL. ACCOMPLISHED ENGINE RUN LEAK CHECK IAW AMM 71-00-00. NO LEAKS NOTED. OK FOR SERVICE.