SPRING
FILTER (WITH
CHECK VALVE)
GASKET
FUEL INLET
NUT
Chapter
C
: Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair
56
Replacing Fuel Injection System Filters
Fuel system pressure must be relieved to change the-
filter on a fuel injected engine. Several methods are
used to relieve fuel pressure; follow the Service Manual
guidelines. Position a drain pan under the work area to
catch spilled fuel. To replace a high-pressure filter with
threaded connections, figure 3-4:
1. Disconnect the fuel lines at both ends of the filter
canister with an appropriate flare nut wrench. Use
a back-up wrench to hold the filter while loosening
the fuel line fitting.
2. Loosen the filter canister mounting bracket fasten-
ers, if necessary, and remove the filter from the
bracket.
3. Replace any O-rings, gaskets, or sealing washers
with new ones.
4. Start each fuel line by hand to prevent crossthread-
ing of the nut. Check to be sure the filter outlet is
facing toward the engine.
5. Install the filter canister in its mounting bracket.
Tighten the bracket fasteners, then tighten each
fuel line nut securely with a flare nut wrench.
Replacing Carburetor and Throttle Body Inlet Filters
There are two major types of inlet filters, the inlet nut fil-
ter and the inlet filter screen assembly, used on domes-
tic carbureted engines.
Inlet Nut Filter or Screen
Remove the air cleaner assembly to access the filter.
The fuel line may install to the carburetor with either a
flare nut or banjo fitting. Disconnect the fitting, separate
the fuel line from the inlet nut, plug or cap the line, and
move it out of the way. Remove the fuel inlet nut and lift
out the filter and spring, figure 3-5.
Install the spring and new filter element. Some filters
contain a check valve to shut off fuel flow in case of a
rollover accident. The open end of the filter must face
toward the nut. Fit a new gasket on the inlet nut, or fit
two new sealing washers on the banjo fitting. Install the
unit, tighten it to specifications, and reattach the fuel
line.
Throttle Body Inlet Screen
To replace the inlet screen on an engine with throttle
body fuel injection (TBI), relieve fuel system pressure be-
fore disconnecting fittings. To disconnect the fuel line,
hold the inlet nut with an open-end wrench and loosen
the fuel line with a second open-end wrench.
Plug or cap the line and move it out of the way, then re-
move the fuel inlet nut. Reach inside the inlet bore with-
needle nose pliers, grasp the slotted end of the filter-
screen assembly, and remove it with a twisting motion.
Install a new filter screen assembly in the inlet bore.
Thread the inlet nut in place, tighten to specifications,
and reinstall the fuel line.
FUEL PUMP AND PRESSURE CONTROLS
To operate efficiently, the engine must be supplied with
a constant flow of clean pressurized fuel. Incorrect fuel
pressure and low fuel volume can cause starting and
driveability problems. The most effective way to check
fuel pump operation is by pressure testing the system.
VAPOR BYPASS
NIPPLE
FUEL
INLET
DIRECTION OF
FUEL FLOW
FUEL
OUTLET
Fig. 3-4.
Cut-away of a typical high-pressure fuel injection filter.
Fig. 3-3.
Inline fuel filter with a vapor bypass fitting.
Fig. 3-5.
Typical inlet nut filter assembly.
Содержание ASE-A8
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