Fault Isolation; Recommended Approach To Fault Isolation; Fault Isolation Guide - Lycoming IO-390-D Series Maintenance Manual

IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual

1. Recommended Approach to Fault Isolation

A. Refer to the Fault Isolation Guide in Table 1.
B. Visually examine the engine for indications of obvious problems, such as intake and exhaust
valve leaks, physical damage to ignition wires and ignition harness, blocked breathers, fuel
and oil stains, etc.
C. Review maintenance logs to identify any trends or possible causes.
D. Discuss any operational problems with the pilot to identify background, details or incidents
of unusual operation.
E. Record all findings and corrective action.

2. Fault Isolation Guide

A. The Fault Isolation Guide in Table 1 shows the more common and recurring problems,
causes, and corrective actions. Continue from the simplest to the most complex possible
causes.
B. The "Ref." column in Table 1 contains references to the following:
(1) A numeric entry such as "72-00" refers to a chapter in this manual.
(2) IOM refers to the IO-390-D Series Engine Installation and Operation Manual.
(3) AMM refers to the Airframe Manufacturer's Manual.
(4) POH refer to the Pilot's Operating Handbook.
Problem
Engine will not start
or starts with
difficulty
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March 2020

12-30 - FAULT ISOLATION

Fault Isolation Guide
Cause
Incorrect starting
procedure
Throttle valve open too
far
Discharged battery
Faulty starter
No fuel or low fuel level
No fuel flow
Blockage in fuel line
Table 1
Corrective Action
Obey starting procedures or the Pilot's
Operating Handbook.
Set the throttle control approximately
1/4 (of the length of throttle control
travel) open for about 800 rpm.
Replace with a charged battery.
Complete the "Starter Replacement"
procedure.
Complete a check of the fuel supply.
Service as required.
1. Disconnect the fuel line.
2. Complete a check of the fuel flow.
3. Examine for evidence of leaks and
correct as required.
4. Clean the filters, strainers, lines, or
fuel valves.
Ref.
IOM
POH
AMM
AMM
72-70
AMM
73-10
12-30
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