A B737-700 PILOT REPORTS THE MASTER CAUTION LIGHT WOULD NOT ILLUMINATE WHEN THE LEFT OR RIGHT CENTER TANK FUEL PUMPS LOW PRESSURE LIGHTS CAME ON; EVEN WHEN THE RECALL LIGHT WAS PRESSED.

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AT 2000 LBS OF FUEL REMAINING IN THE CTR FUEL TANK; I OPENED THE XFEED VALVE AND TURNED OFF THE L CTR TANK FUEL PUMP. A SHORT TIME LATER; I NOTICED THAT THE OVERHEAD CTR TANK R FUEL PUMP LOW PRESSURE LIGHT WAS ILLUMINATED STEADY WITHOUT THE MASTER CAUTION LIGHT OR THE FUEL LIGHT BEING ILLUMINATED. I PRESSED THE RECALL LIGHT AND STILL MASTER CAUTION LIGHT WAS NOT ILLUMINATED. I TURNED OFF THE R CTR TANK FUEL PUMP AND WONDERED IF THERE WAS A PROB WITH THE MASTER CAUTION SYS. FOR THIS REASON; I TURNED ON THE L CTR TANK FUEL PUMP. ITS LOW PRESSURE LIGHT ILLUMINATED STEADY; AGAIN WITHOUT THE MASTER CAUTION LIGHT ILLUMINATING. PER THE 700 FRM THE MASTER CAUTION LIGHTS SHOULD HAVE ILLUMINATED. THE FO AND I GOT DISTR DISCUSSING AND WRITING UP THE ACFT DISCREPANCY IN THE LOGBOOK; SO WE GOT A LITTLE HIGH ON OUR XING RESTR. WE NOTIFIED CTR THAT WE WERE GOING TO BE ABOUT 1500 FT HIGH. CTR THEN CLRED US ON A MORE DIRECT RTE ON THE ARR; DELETING THE ALT RESTR. THE TWO OF US SHOULD HAVE SPENT MORE TIME FLYING THE ACFT THAN WORRYING ABOUT A MINOR ACFT PROB. AFTER LNDG; I SPOKE WITH DISPATCH AND MAINT CTL TO EXPLAIN THE PROB; AND TO SEE IF WE COULD PUT ON THE SCHEDULED FUEL LOAD. MAINT CTL SAID THAT THERE WAS NO RESTR TO LOAD FUEL; AND THAT WE WOULD SIMPLY HAVE THE MAINT PERSON SIGN OFF THE ACFT UNDER MEL SYS ANNUNCIATOR LIGHTS (PLT'S GLARE SHIELD). WHEN THE MAINT PERSON ARRIVED; HE HAD DIFFICULTY UNDERSTANDING THE PROB SINCE THERE WAS NOW 2000 LBS OF FUEL IN THE CTR TANK AND WE COULD NOT GET THE CTR TANK LOW PRESSURE LIGHT TO ILLUMINATE. WE POINTED OUT OUR CONCERN OVER USING MEL; SINCE THE ANNUNCIATOR LIGHTS WERE WORKING CORRECTLY. THE MAINT PERSON SAID THE SYS WAS OPERATING NORMALLY. I SHOWED HIM FRM AND EXPLAINED THAT THE SYS WAS NOT WORKING CORRECTLY FROM WHAT I READ. HE EXPLAINED THAT THERE WAS SOME BOEING CIRCULAR OUT THAT SAID OTHERWISE. AFTER SPEAKING WITH MAINT CTL; THE MAINT PERSON USED A DIFFERENT MEL; FUEL BOOST PUMPS (CTR TANK); TO RELEASE THE ACFT. HE PULLED THE CIRCUIT BREAKERS AND WE COULD NOT USE THE 2000 LBS OF FUEL IN THE CTR TANK. IT TOOK ALMOST 1 HR TO GET ALL OF THE MAINT ISSUES SOMEWHAT CLARIFIED TO OUR NEXT FLT. THERE SEEMS TO BE SOME MAJOR CONFUSION ON HOW THE NEW CTR TANK FUEL PUMP AUTOMATIC SHUTOFF SYS WORKS IN RELATION TO THE MASTER CAUTION SYS. MANY PLTS ARE STATING THAT THIS IS EXACTLY THE WAY MANY ACFT IN THE INVENTORY ARE NOW WORKING. A NOTICE SHOULD BE RELEASED EXPLAINING EXACTLY WHAT INDICATIONS WILL BE PRESENTED IN THE COCKPIT. ALSO; SINCE THIS IS ONE OF THE NONSTANDARD ACFT; I WONDER IF THIS IS JUST AN ISSUE WITH THIS JET. THE MEL SHOULD BE EXPANDED TO ALLOW THE OP OF THE CTR TANK FUEL PUMPS IN THIS SITUATION SINCE EVERYTHING EXCEPT THE MASTER CAUTION SYS FOR THE CTR TANK WAS FULLY OPERATIONAL. ALSO; THE FOM/FRM NEEDS TO BE CLARIFIED SINCE MORE AND MORE CONTRADICTORY STATEMENTS BTWN THE 2 REFS AND ACTUAL ACFT SYS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THEIR B737-700'S HAVE THE CENTER FUEL TANK WITHOUT ANY OF THE FWD OR AFT AUX CENTER FUEL TANKS. MOST; IF NOT ALL OF THEIR ACFT CENTER FUEL TANK PUMPS; TWO EACH TOTAL (CENTER LEFT AND RIGHT); HAVE BEEN CHANGED TO THE MODIFIED TYPE WHICH ARE SUPPOSED TO ILLUMINATE THE MASTER CAUTION WHEN ANY OF THE CENTER PUMP(S) HAS A LOW PRESSURE CONDITION FOR MORE THAN 5 SECONDS. REPORTER NOTES HE HAS SEEN THIS SAME MASTER CAUTION FAILURE TO ILLUMINATE ON OTHER -700'S; BUT; THIS WAS THE FIRST TIME HE HAS FLOWN THEIR NON-STANDARD B737-700 AND REALIZED THE SAME MASTER CAUTION FAILURE PROBLEM EXISTED. REPORTER STATED MAINT SUSPECTS THE LOW PRESSURE SENSOR(S); ASSOCIATED WITH THE MASTER CAUTION ANNUNCIATOR; IS PICKING UP IT'S SIGNAL FROM ANOTHER LOCATION.