Failure of the Feedback of the Fuel Return Valve on Engine 1

TASK 73-10-00-810-821-A
Failure of the Feedback of the Fuel Return Valve on Engine 1

1. Possible Causes

ECU [4000KS]
fuel return valve
harness J7
harness J8

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 73-11-50-000-002	Removal of the Fuel Return Valve (FRV)
AMM 73-11-50-400-002	Installation of the Fuel Return Valve
AMM 73-21-50-000-040	Removal of the HJ7 Harness for SAC Engines
AMM 73-21-50-000-041	Removal of the HJ8 Harness for SAC Engines
AMM 73-21-50-400-040	Installation of the HJ7 Harness for SAC Engines
AMM 73-21-50-400-041	Installation of the HJ8 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 73-10-00-710-088-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 73-10-00-810-074-A ** ON A/C NOT FOR ALL

A. The fault is generated when the ECU detects a disagreement in the indication of the fuel return valve position given by the switch of channel A compared with the switch of channel B.
(1) If the test does not give the maintenance message FRV (SW), J7/J8, ECU but the fault is repetitive:
(a) Inspect the J7 and J8 harnesses and associated connectors to the fuel return valve and ECU for sign of looseness, damage or contamination ASM 732518.

Re-tighten, clean or replace harness as required.
If no defect is found either or on the harness or the connector no further action is due.

(b) If the fault continues or is repetitive:

Replace the fuel return AMM 73-11-50-000-002 and AMM 73-11-50-400-002.

Replace the harness J7 AMM 73-21-50-000-040 and AMM 73-21-50-400-040.

(d) If the fault continues:

Replace the harness J8 AMM 73-21-50-000-041 and AMM 73-21-50-400-041.

(e) If the fault continues:

Replace the ECU AMM 73-21-60-000-001 and AMM 73-21-60-400-001;

(2) If the test gives the maintenance message FRV (SW), J7/J8, ECU:

Disconnect the harnesses J7 and J8 from the ECU and do a resistance check on the J7 and J8 harness between:
. pins 31 and 14 (< 5 ohms)
. pins 31 and 33 (> 10 megohms).
. pin 31 and the ground (> 10 megohms).

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

replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

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

Disconnect the harness J7 and J8 from the fuel return valve and do a check of the resistance on the valve switch connectors on each channel between:
. pins 3 and 4 (< 5 ohms)
. pin 3 and the ground (> 10 megohms).

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

replace the fuel return valve AMM 73-11-50-000-002 and AMM 73-11-50-400-002.

2 If the resistance values are in the specified limits:

replace the harness J7 AMM 73-21-50-000-040 and AMM 73-21-50-400-040 and/or the harness J8 AMM 73-21-50-000-041 and AMM 73-21-50-400-041.

Subtask 73-10-00-710-089-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.A.

[Rev.8 from Aug 2018] 2026.04.04 04:35:15 UTC