53
Chapter
C
FUEL, AIR INDUCTION, AND EXHAUST
SYSTEMS DIAGNOSIS AND REPAIR
To run efficiently, an engine must be supplied with a
constant flow of clean pressurized fuel and filtered air in
precisely metered amounts. In addition, the exhaust
system must effectively carry combustion gases out of
the engine, without excessive backpressure. Electroni-
cally controlled engines monitor operating conditions
through a variety of sensors and adjust the airfuel mix-
ture for optimum performance.
If the balance of the air-fuel mixture is upset, driveabili-
ty suffers. Problems of hard starting, no starting, hesita-
tion, surging, power loss, stalling, misfiring, incorrect
idle speed, poor idle quality, poor fuel mileage, and
dieseling can be caused by a fuel or air induction defi-
ciency. However, mechanical, electrical, electronic, or
ignition problems may have similar symptoms. There-
fore, it is important to isolate the source of the problem
before attempting repairs. To isolate the problem to a
specific system, perform the diagnostic tests detailed in
the previous chapters of this book.
FUEL SYSTEM SERVICE
When fuel system service is required, observe these
safety precautions:
• Keep open flames and sparks away from the vehi-
cle
• Do not smoke near any part of the fuel system
• Work in a well-ventilated area
• Cap or plug all disconnected fuel lines
• Disconnect the battery ground cable before remov-
ing or replacing fuel system parts to preven acci-
dental arcing
Inspection
Because of its many parts and connecting lines, the fuel
system may develop leaks at several points. Keep in
mind any leak, or restriction, will affect operating pres-
sure and can cause a driveability problem. Begin with a
thorough inspection of the entire fuel system. To check
for damage and safety defects:
1. Inspect the fuel tank for:
• Physical damage and leakage at fittings, con-
nections, and seams
• Plugged vents and damaged vent tubes and-
connecting lines
• Filler tube and filler tube cap condition and-
proper venting
• Leakage at the filler tube, vent line connections,
and fuel gauge sending unit
• Secure mounting; tighten tank holddown straps
if necessary
• Signs of internal contamination
2. Inspect fuel lines and hoses for:
• Loose connections and signs of seepage
• Pinched or crushed lines
• Weathered, damaged, or deteriorated hoses
3. Inspect fuel filters for:
• Loose connections and signs of leakage
• Signs of chafing or other exterior damage
• Blockage and contamination
4. Check the fuel pump for:
• Leakage
• Secure mounting
• Loose hoses, fittings, and connections
5. Check the intake manifold for:
• Fuel and air leaks
• Proper routing of the vacuum lines
• Deterioration of vacuum lines
• Loose carburetor, throttle body, or injector
mounting
6. Verify that the fuel in the vehicle tank is:
• Fresh, not stale or old
• Free from water or other contaminants
7. Refer to the Service or Diagnostic Manual for the
correct troubleshooting procedure to follow, figure
3-1.
Summary of Contents for ASE-A8
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