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 4. Fault Isolation
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R A. Check the log book/crew report and Post Flight Report (PFR) for IDG
R  failure warning or message. This failure is triggered if the engine oil temperature goes beyond 135 deg.C (275 deg.F) possibly caused by too high IDG oil temperature.
 (1) If IDG failure warning or messages are present, do the related trouble shooting procedure.

 (2) If no IDG failure warning or messages are present:

 - check the PFR and look for failure messages including the following R words: FLSCU; fuel level sensing; FRV, J7 and/or FRV, J8; EIU; EIU R (031) for possible causes of forced closure of the fuel return R valve.
 (a) If messages are present, do the related trouble shooting procedure.

 (b) If no failure messages are present:

 - get a sample of oil from the engine oil tank.
 1 If you can smell fuel presence in the engine oil:
_
 - replace the IDG oil/fuel heat exchanger (Ref. AMM TASK 79-21-20-000-002) and (Ref. AMM TASK 79-21-20-400-002),

 - do a check of the lubrication unit magnetic plugs and screens (Ref. AMM TASK 79-21-10-210-002).

 2 If nothing is found:
_
 - do a functional check of the fuel return valve to make sure that it operates correctly (Ref. AMM TASK 73-11-50-210-002)
 a If the valve does not operate correctly:
_
 - replace the valve (Ref. AMM TASK 73-11-50-000-002) and (Ref. AMM TASK 73-11-50-400-002).
 b If the valve operates correctly:
_
 - replace the FADEC oil temperature sensor (not 4004EN) (Ref. AMM TASK 79-31-40-000-002) and (Ref. AMM TASK 79-31-40-400-002).
 3 If the fault continues:
_
 - replace the ECU (4000KS) (Ref. AMM TASK 73-21-60-000-001) and (Ref. AMM TASK 73-21-60-400-001).
 4 If the fault continues:
_
 - replace the pressure-holding valve (125QM) (Ref. AMM TASK 28-16-41-000-001) and (Ref. AMM TASK 28-16-41-400-001).
 5 If the fault continues:
_
 - replace the fuel recirculation check-valve (Ref. AMM TASK 28-16-42-000-001) and (Ref. AMM TASK 28-16-42-400-001).
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 B. Test

 (1) Do a minimum idle check (Ref. AMM TASK 71-00-00-710-006).

 (2) Repeat the fault isolation procedure if the fault continues.

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