Chapter
C
: Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair
55
Some systems use high-pressure fittings with O-ring
seals instead of traditional flare connectors. Inspect the
O-ring for damage whenever the fitting is disconnected
and replace the O-ring if necessary.
TUBING
TUBING
FLARE
NUT
NUT
CONNECTOR
CONNECTOR
SLEEVE
BODY
STEEL TUBE
FLARE NUT FITTING
COMPRESSION FITTING
SPRING-LOCK FITTING
PUSH-LOCK FITTING
O-RINGS
GARTER SPRING
TUBING
CONNECTOR
CLIP
LOCKTAB
Fig. 3-2.
Typical fuel line connections.
Replacement O-rings must be specifically designed for
fuel system use. Tighten fittings to the specified torque-
value to prevent O-ring damage.
Fuel Filter Replacement
The fuel filter is the only item of the system that must be
changed at regular service intervals. Replacement rec-
ommendations vary by manufacturer, engine, and type
of filter used. Always begin by removing the fuel filler
cap to relieve any pressure in the tank. After replacing a
filter, start and run the engine to check for leaks. There
are two common fuel filter designs:
• Inline
• Carburetor or throttle body inlet
Some vehicles use multiple fuel filters. They can be lo-
cated in the fuel pump, near the fuel tank, and near the-
carburetor. The filter closest to the fuel tank is the first-
to become restricted, and to require replacement.
Replacing Inline Filters
Disposable inline fuel filters are common and may be
used on both carbureted and fuel-injected engines. The
filter may be located in the engine compartment or un-
derneath the vehicle near the pump. Inline filters on a
low-pressure fuel system generally have a nipple at
each end that attaches to a length of hose secured by a
clamp. The fuel filter attaches with threaded connec-
tions on some high-pressure fuel injection applications;
spring-lock connectors are used on others. All filters are
designed to allow flow in only one direction. Look for an
arrow or other directional indicator on the filter housing,
and be sure to properly orient it on installation.
When replacing the filter on a low-pressure system, it is
good practice to install new hose clamps along with the
new filter to prevent leakage. Always replace spring-
type clamps when replacing the fuel filter. To change a
low-pressure inline filter:
1. Place a drain pan under the filter to catch spills.
2. Remove the clamp at one end and pull the hose
from the filter fitting.
3. Attach the hose to the new filter making sure it
faces the proper direction. Then, tighten the clamp
securely.
4. Remove the clamp at the other end and pull the
hose from the filter fitting. Attach this hose to the
corresponding fitting on the new filter and tighten
the clamp.
5. If the filter has a vapor bypass line, switch the line
from the old filter to the new one, figure 3-3.
Summary of Contents for ASE-A8
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