A B737-400 FLT CREW NOTED THEY HAD NO RNAV CAPABILITY BECAUSE OF AN MEL'S FUEL QUANT INDICATOR AND NO VNAV CAPABILITY ON THE FMC.

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FLYING 737-400 WITH SEVERAL MEL'S; INCLUDING FUEL QUANTITY GAUGE INOP. DISPATCH REQUESTED AND ATC ASSIGNED RNAV DEP. UPON ENTERING WT AND BAL INFO INTO CDU; WE REALIZED THAT PREDEP COULD NOT BE COMPLETED DUE TO NO FUEL QUANTITY AND NO VNAV CAPABILITY ON THE FMC. NO RWY UPDATE PROMPT COULD BE GENERATED. BECAUSE ACFT CAPABILITY FOR RNAV DEP DEGRADED TO; AT THE VERY LEAST; BELOW THAT OF THE 737-300; I REFUSED RNAV DEP AND REQUESTED THE APPROPRIATE SID. AFTER A 30-60 SECOND DELAY AND CHANGING FMC RTE; TWR RECLRED AND WE DEPARTED. I INFORMED DISPATCHER; SENIOR CHK AIRMAN; AND THE ONCOMING CREW OF THE RNAV DEGRADATION OF THE ACFT; AND THEN SUBMITTED THIS RPT. DISPATCH BELIEVED ACFT CAPABLE OF RNAV DEP BECAUSE THERE IS EITHER NO APPLICABLE MEL DEGRADING THE ACFT; OR IF THERE IS AN APPLICABLE MEL; BOTH DISPATCH AND AVIONICS MAINT IS UNAWARE OF IT. UPDATE BULLETIN TO REFLECT THIS ADDITIONAL DISABILITY OF THE 737-400 TO PERFORM RNAV DEPS WHEN THE FMC IS UNABLE TO GENERATE A RWY UPDATE PROMPT. UPDATE THE MEL TO REFLECT THE AFOREMENTIONED AND ENSURE THAT DISPATCH AND MAINT ARE INFORMED.