A ROCKWELL DARTER COMMANDER CREW ALMOST RAN OUT OF FUEL DUE TO VERY HIGH FUEL FLOW FOR AN UNKNOWN REASON.

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ACFT WAS TO BE FLOWN FROM PWA TO BJC WITH A STOP IN LBL FOR FUEL. FLT DEPARTED PWA AT XA30Z; 4500 FT MSL CRUISE; MYSELF FLYING; ANOTHER FLT INSTRUCTOR IN THE R SEAT. ENRTE THE RADIOS WERE WEAK AND SCRATCHY AND THE FUEL GAUGES WERE INACCURATE (NORMAL FOR MOST TRAINING ACFT). WE ARRIVED IN LBL AT XF00Z; TOPPED THE TANKS (40 GALLONS USABLE); AND CALCULATED THE FUEL BURN ENRTE; ABOUT 8 GALLONS PER HR. AFTER FILING A VFR FLT PLAN (LBL TO BJC; 3+30 ENRTE TIME; 5+0 HRS FUEL); WE DEPARTED LBL AT XF30Z. DUE TO INACCURATE FUEL GAUGES; WE SWITCHED TO THE R TANK (RATHER THAN BOTH) FOR 1/2 HR WHILE ENRTE. APPROX 10 NM SE OF BJC; ENG MISSED; THEN QUIT COMPLETELY. PLT BANKED ACFT TO R; SWITCHED FUEL SELECTOR TO L TANK AND INITIATED A CLB FROM 7500 FT MSL. ENG CONTINUED STARTING AND STOPPING FOR THE REMAINDER OF THE FLT. CONTACTED BJC TWR AND TOLD THEM OF ENG PROBS. CONTINUED CLB TO 8500 FT MSL UNTIL 4 NM SE OF BJC. TWR CLRED US TO LAND RWY 29L OR RWY 29R. LNDG WAS MADE WITHOUT FURTHER INCIDENT. ON THE GND AT BJC; HOBBS TIME 3.5 HRS; FUEL GAUGES BOTH INDICATED EMPTY. POSSIBLE CAUSES: PROB SOMEWHERE IN THE FUEL SYS; POSSIBLE FUEL LEAK. RECURRENCE PREVENTION: NEXT TIME MAKE AN EXTRA STOP FOR FUEL. MOST GA ACFT FUEL GAUGES ARE INACCURATE; UNLESS THEY READ EMPTY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS FLYING A ROCKWELL DARTER COMMANDER. MECHS AT HIS LCL FBO NEVER WERE ABLE TO FIND THE PROB WITH THE FUEL FLOW. EACH TIME THAT THE RPTR FILLED THE TANKS; HE HAD THEM FILLED TO OVERFLOWING. BOTH HE AND HIS FLYING PARTNER CHKED THE FUEL LEVEL BEFORE DEP. ANOTHER PLT THAT FLEW THIS ACFT NOTED THAT THE FUEL FLOW RATE SEEMED TO VARY FROM LEG TO LEG. THE RPTR HAS NOT HEARD FROM THE FAA ON THIS.