Jeep cherokee 1989, Owner'S Manual

Page: 149 / 336

Chapter
4
Fuel and exhaust systems
4-1
2.5 To relieve the fuel pressure on an MPI-equipped
vehicle, remove the cap from the pressure test port, place
some shop towels underneath t o absorb sprayed fuel
. .
.
2.7
. . .
then depress the valve in the test port w i t h a small
screwdriver or pin punch
-
wear safety goggles during pressure
relief t o protect your eyes from spraying fuel
2 Fuel pressure relief (fuel-injected vehicles)
Refer to illustrations 2.5 and 2.7
Warning: Gasoline is extremely flammable, so extra precautions must
be taken when working on any part of the fuel system. Do not smoke
or
w open flames or bare light bulbs in or near the work area. Also,
don't work in a garage where a natural gas appliance such as a water
heater or clothes dryer is present.
TBI-equipped vehicles
1
The fuel system of vehicles equipped with Throttle Body injection
is only under pressure when the fuel pump is operating. As long
as the fuel pump is not operating, TBI fuel system components can
be removed without the need t o release system pressure.
MPl-equipped vehicles
2 The MPI system is under a constant fuel pressure of 9 t o 19 psi.
Before attempting to service any fuel supply or return component on
vehicles equipped with this system, release the fuel pressure.
3 Detach the cable from the negative battery terminal.
4 Remove the fuel tank filler cap t o relieve fuel tank pressure.
5
Remove the cap from the pressure test port on the fuel rail (see
illustration).
6
Place shop towels under the pressure test port t o absorb fuel when
the pressure is released from the fuel rail.
7 Using a small screwdriver or pin punch, push the test port valve
in t o relieve fuel pressure (see illustration). Absorb the spilled fuel with
the shop towels.
8
Remove the shop towels.
9 Install the cap on the pressure test port.
3 Fuel pumplfuel pressure
-
check
Warning: Gasoline is extremely flammable, so extra precautions must
be taken when working on any part of the fuel system. Do not smoke
or
w open flames or bare light bulbs in or near the work area. Also,
don't work in a garage where a natural gas appliance such as a water
hearer or clothes dryer is present.
Mechanical pump (carburetor equipped vehicles)
Quick check
1 Detach the cable from the negative battery terminal.
Remove the air cleaner assembly (see Section 7).
3
Detach the fuel inlet fitting from the carburetor and place the end
of the inlet line in a metal or plastic container.
4
Attach the cable t o the negative battery terminal.
5 Hook up a remote starter switch, if available, in accordance with
the manufacturer's instructions. If you don't have a remote starter
switch, you will need an assistant for the following procedures.
6
Disable the ignition coil by detaching the primary lead wires (see
Chapter 51.
7 With the fuel line directed into the container, have an assistant
turn the ignition key to Start and crank the engine for about ten seconds.
8 Fuel should be emitted from the fuel line in well-defined spurts.
If it isn't, there is a problem somewhere in the fuel delivery system.
The following tests will determine where the problem lies.
Pressure test
Refer to illustration 3.
Note: You will need a fuel pressure gauge, a hose restrictor and a
of flexible hose to perform the following procedures.
9
If the vehicle has a four-cylinder engine, detach the fuel return hose
at the fuel filter and plug the fitting on the filter.
10 Attach
a
pressure gauge, restrictor and flexible hose between the
fuel inlet fitting or the fuel filter and the carburetor (see illustration).
I
INLET
(FROM FUEL PUMP)
3.10 The proper setup for the fuel pump pressure and
capacity tests (if you don't have
a hose restrictor, a pair of
vise grips w i t h padded jaws will work just as
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