Failure of the HMU Fuel Metering Valve on Engine 1

TASK 73-10-00-810-801-A
Failure of the HMU Fuel Metering Valve on Engine 1

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 73-21-10-000-001	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-000-002	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-001	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-002	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-50-000-006	Removal of J7 Harness
AMM 73-21-50-000-040	Removal of the HJ7 Harness for SAC Engines
AMM 73-21-50-400-006	Installation of the J7 Harness
AMM 73-21-50-400-040	Installation of the HJ7 Harness for SAC Engines
AMM 73-21-60-000-001	Removal of the Electronic Control Unit (ECU)
AMM 73-21-60-400-001	Installation of the Electronic Control Unit (ECU)
ASM 732518
AMM 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)

3. Fault Confirmation
Subtask 73-10-00-710-050-A ** ON A/C NOT FOR ALL

A. Do the operational test of the FADEC 1A on the ground (with engine motoring) AMM 73-29-00-710-040.

4. Fault Isolation
Subtask 73-10-00-810-050-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message HMU (FMV):

do a check for line to line short circuit of the harness J7 between the ECU (4000KS) and the hydromechanical unit (HMU) pins J7/27, 28 ASM 732518.

(1) If the wiring is not correct:

(2) If the wiring is correct:

disconnect the cable J7 from the ECU (4000KS) and do a check of the ECU cable resistance between:
. pins 27 and 28 (17 to 23 Ohms).

(a) If the resistance values are in the specified limits:

(b) If the resistance values are out of the specified limits:

disconnect the cable J7 from the HMU and do a resistance check of the HMU between:
. pins 27 and 28 (17 to 23 Ohms).

1 If the resistance values are in the specified limits:

2 If the resistance values are out of the specified limits:

Subtask 73-10-00-810-050-C ** ON A/C NOT FOR ALL