Narrative:

At 2000 pounds of fuel remaining in the center fuel tank; I opened the xfeed valve and turned off the left center tank fuel pump. A short time later; I noticed that the overhead center tank right 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 right center tank fuel pump and wondered if there was a problem with the master caution system. For this reason; I turned on the left center 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 first officer and I got distraction discussing and writing up the aircraft discrepancy in the logbook; so we got a little high on our crossing restr. We notified center that we were going to be about 1500 ft high. Center then cleared us on a more direct route on the arrival; deleting the altitude restr. The two of us should have spent more time flying the aircraft than worrying about a minor aircraft problem. After landing; I spoke with dispatch and maintenance control to explain the problem; and to see if we could put on the scheduled fuel load. Maintenance control said that there was no restr to load fuel; and that we would simply have the maintenance person sign off the aircraft under MEL system annunciator lights (pilot's glare shield). When the maintenance person arrived; he had difficulty understanding the problem since there was now 2000 pounds of fuel in the center tank and we could not get the center tank low pressure light to illuminate. We pointed out our concern over using MEL; since the annunciator lights were working correctly. The maintenance person said the system was operating normally. I showed him frm and explained that the system was not working correctly from what I read. He explained that there was some boeing circular out that said otherwise. After speaking with maintenance control; the maintenance person used a different MEL; fuel boost pumps (center tank); to release the aircraft. He pulled the circuit breakers and we could not use the 2000 pounds of fuel in the center tank. It took almost 1 hour to get all of the maintenance issues somewhat clarified to our next flight. There seems to be some major confusion on how the new center tank fuel pump automatic shutoff system works in relation to the master caution system. Many pilots are stating that this is exactly the way many aircraft 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 aircraft; I wonder if this is just an issue with this jet. The MEL should be expanded to allow the operation of the center tank fuel pumps in this situation since everything except the master caution system for the center tank was fully operational. Also; the fom/frm needs to be clarified since more and more contradictory statements between the 2 references and actual aircraft system. Callback conversation with reporter revealed the following information: reporter stated their B737-700's have the center fuel tank without any of the fwd or aft auxiliary center fuel tanks. Most; if not all of their aircraft 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(south) 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 maintenance suspects the low pressure sensor(south) associated with the master caution annunciator is picking up its signal from another location.

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Original NASA ASRS Text

Title: 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.

Narrative: 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 ITS SIGNAL FROM ANOTHER LOCATION.

Data retrieved from NASA's ASRS site as of May 2009 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.