Fuel - During Aircraft Ops (That Include A Refuel Without A Break In Electrical Power) The CTR TK Pumps Do Not Operate After The CTR TK Is Refueled From Empty

TASK 28-21-00-810-845-A
Fuel - During Aircraft Ops (That Include A Refuel Without A Break In Electrical Power) The CTR TK Pumps Do Not Operate After The CTR TK Is Refueled From Empty

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

1. Possible Causes

RELAY-REFUEL/DEFUEL CTL PNL DOOR POSITION [14QU]
RELAY-CTR TANK PUMP 1, LATCHED OFF (67QA)
RELAY-CTR TK LOW LEVEL, N#Auml# 1 [45QA]
aircraft wiring
RELAY-CTR TANK PUMP 2, LATCHED OFF (68QA)
RELAY-CTR TK LOW LEVEL, N#Auml# 2 [46QA]
RELAY-L WING TK REFUEL VALVE CONTROL [15QU]
RELAY-R WING TK REFUEL VALVE CONTROL [16QU]
RELAY-CTR TK REFUEL VALVE CONTROL [17QU]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 28-25-00-810-805-A	Refuel/Defuel Floodlight Failure
AMM 12-11-28-650-003	Pressure Refuel with Automatic Control
ESPM 2052210
ESPM 2052220
ESPM 2053210
AMM 28-21-00-720-001	Functional Test of the Center-Tank Fuel Control
ASM 282104
ASM 282501
ASM 315402

3. Fault Confirmation
Subtask 28-21-00-710-092-A ** ON A/C NOT FOR ALL

A. Test

In normal operation the two center-tank pump circuits are reset (de-latched) when the refuel panel door is opened ASM 282104 and ASM 282501.

Work-a-round (not a troubleshooting fix)
You can get the same result if the P/BSW-CTR TK/MODE SEL/AUTO (48QA) is released out (set to MAN) and then pushed in (set/returned to AUTO) again.

Cockpit Refuel (if installed)
If the center-tank fuel is all used (during the aircrafts previous flight(s)) the cockpit refuel method does not automatically de-latch the center-tank fuel-pumps 1 and 2 (when the center-tank is refuelled).

To de-latch the pumps you must use one of the two methods given before.
(1) Do the Functional Test of the Center-Tank Fuel Control AMM 28-21-00-720-001.
(a) If:

the two center tank pumps, do not delatch, do Para. 4.A., step (1)
the center tank (left side) pump 1, does not delatch, do Para. 4.A., step (2)
the center tank (right side) pump 2, does not delatch, do Para. 4.A., step (3)
the two center tank pumps delatch correctly, no troubleshooting work steps are necessary.

Subtask 28-21-00-710-092-B ** ON A/C NOT FOR ALL

A. Test

In normal operation the two center-tank pump circuits are reset (de-latched) during a refuel ASM 282104 and ASM 282501.

NOTE: The de-latch system operates for all normal electrically controlled pressure refuel procedures. It does not operate when the refuel-valve manual plungers are used.

The center-tank de-latch occurs when one of the relays that follow operates (is energized):

VALVE-REFUEL, L WING TK (7QU)
VALVE-REFUEL, R WING TK (8QU)
VALVE-REFUEL, CTR TK (10QU).

When one of the refuel valve control relays is energized:

the A contacts of the applicable relay apply 28VDC to the related refuel valve solenoid to open the valve
the B contacts of the same relay remove the ground of the latch hold-on circuit and cause the latch system to de-energize (return to its initial condition).

Work-a-round (this is not a troubleshooting fix)
You can get the same result if the P/BSW-CTR TK/MODE SEL/AUTO (48QA) is released out (set to MAN) and then pushed in (set/returned to AUTO) again.
(1) Do the Functional Test of the Center-Tank Fuel Control AMM 28-21-00-720-001.
(a) If:

the two center tank pumps, do not delatch, do Para. 4.A., step (1)
the center tank (left side) pump 1, does not delatch, do Para. 4.A., step (2)
the center tank (right side) pump 2, does not delatch, do Para. 4.A., step (3)
the two center tank pumps delatch correctly, no troubleshooting work steps are necessary.

4. Fault Isolation
Subtask 28-21-00-810-091-A ** ON A/C NOT FOR ALL

A. Procedure
(1) If the two center tank pumps, do not reset (delatch) do the steps that follow:
(a) Open the (applicable) access door (192MB/522KB/622KB) to the refuel control panel 800VU AMM 12-11-28-650-003.
(b) If the floodlight adjacent to the refuel control panel door:

does not come on, do the TSM procedure 'Refuel/Defuel Floodlight Failure' (Ref. TSM TASK 28-25-00-810-805).
does come on, do step (c).

NOTE: A failure of the relay (C and D sets of) contacts to open correctly can cause the latch to remain on.

(2) If the center tank (left side) pump 1, does not reset (delatch) do the steps that follow:
(a) Do a check of and replace, if necessary, the relays that follow:

RELAY-REFUEL/DEFUEL CTL PNL DOOR POSITION [14QU]
RELAY-CTR TANK PUMP 1, LATCHED OFF (67QA)
RELAY-CTR TK LOW LEVEL, N#Auml# 1 [45QA] .

(b) Do a wiring check of the aircraft wiring (latch hold-on (ground) wire) ASM 282104 and ASM 315402 between:

relay 14QU, terminal C3 and relay 67QA, terminal 2
relay 67QA, terminal A and relay 45QA, terminal X2
relay 45QA, terminal X2 and FLSCU-1 rack connector 7QJ-AA, pin 8B
relay 45QA, terminal X2 and the SDAC acquisition interface ASM 315402 L CTR TK LO LVL.

NOTE: A wiring check means that you test the wire(s) specified as follows:

for contiuity ESPM 2052210
for a short circuit to ground ESPM 2052220
for a short circuit to adjacent wires ESPM 2052220.

These checks are necessary to find a possible short-circuit to ground in the latch hold-on (ground) wire. A short-circuit (as described) can cause the latch to remain on.

(c) Repair all the unserviceable wiring and connectors ESPM 2053210.
(d) Do the test in Para. 3.A.
(3) If the center tank (right side) pump 2 does not reset (delatch), do the steps that follow:
(a) Do a check of and replace, if necessary, the relays that follow:

RELAY-REFUEL/DEFUEL CTL PNL DOOR POSITION [14QU]
RELAY-CTR TANK PUMP 2, LATCHED OFF (68QA)
RELAY-CTR TK LOW LEVEL, N#Auml# 2 [46QA] .

(b) Do a wiring check of the aircraft wiring (latch hold-on (ground) wire) ASM 282104 and ASM 315402 between:

relay 14QU, terminal D3 and relay 68QA, terminal 2
relay 68QA, terminal A and relay 46QA, terminal X2
relay 46QA, terminal X2 and FLSCU-2 rack connector 9QJ-AA, pin 8B
relay 46QA, terminal X2 and the SDAC acquisition interface ASM 315402 R CTR TK LO LVL.

NOTE: A wiring check means that you test the wire(s) specified as follows:

for contiuity ESPM 2052210
for a short circuit to ground ESPM 2052220
for a short circuit to adjacent wires ESPM 2052220.

These checks are necessary to find a possible short-circuit to ground in the latch hold-on (ground) wire. A short-circuit (as described) can cause the latch to remain on.

Subtask 28-21-00-810-091-B ** ON A/C NOT FOR ALL

A. Procedure
(1) If the two center tank pumps do not reset (delatch), do the steps that follow:
(a) Do a check of and replace, if necessary, the relays that follow:

RELAY-L WING TK REFUEL VALVE CONTROL [15QU]
RELAY-R WING TK REFUEL VALVE CONTROL [16QU]
RELAY-CTR TK REFUEL VALVE CONTROL [17QU] .

NOTE: A failure of the relay contacts to open correctly can cause the latch to remain on.

(b) Do a wiring check of the aircraft wiring (latch hold-on (ground) wire) ASM 282501 and ASM 282104 between:

relay 67QA, terminal 2 and relay 17QU, terminal B3
relay 68QA, terminal 2 and relay 17QU, terminal B3
relay 17QU, terminal B2 and relay 16QU, terminal B2
relay 16QU, terminal B3 and relay 15QU, terminal B2
relay 15QU, terminal B2 and ground point.

NOTE: A wiring check means that you test the wire(s) specified as follows:

for contiuity ESPM 2052210
for a short circuit to ground ESPM 2052220
for a short circuit to adjacent wires ESPM 2052220.

These checks are necessary to find a possible short-circuit to ground in the latch hold-on (ground) wire. A short-circuit (as described) can cause the latch to remain on.

(2) If the center tank (left side) pump 1 does not reset (delatch), do the steps that follow:
(a) Do a check of and replace, if necessary, the relays that follow:

RELAY-CTR TANK PUMP 1, LATCHED OFF (67QA)
RELAY-CTR TK LOW LEVEL, N#Auml# 1 [45QA] .

(b) Do a wiring check of the aircraft wiring (latch hold-on (ground) wire) ASM 282104 and ASM 315402 between:

relay 67QA, terminal A and relay 45QA, terminal X2
relay 45QA, terminal X2 and FLSCU-1 rack connector 7QJ-AA, pin 8B
relay 45QA, terminal X2 and the SDAC acquisition interface ASM 315402 R CTR TK LO LVL.

RELAY-CTR TANK PUMP 2, LATCHED OFF (68QA)
RELAY-CTR TK LOW LEVEL, N#Auml# 2 [46QA] .

(b) Do a wiring check of the aircraft wiring (latch hold-on (ground) wire) ASM 282104 and ASM 315402 between:

relay 68QA, terminal A and relay 46QA, terminal X2
relay 46QA, terminal X2 and FLSCU-2 rack connector 9QJ-AA, pin 8B
relay 46QA, terminal X2 and the SDAC acquisition interface ASM 315402 R CTR TK LO LVL.

[Rev.8 from Aug 2018] 2026.04.04 04:28:39 UTC