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1.Release residual pressure
from the fuel pipe line to prevent fuel gush out (Refer
to  ).
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2.Disconnect the
high-pressure fuel hose at the main pipe side.
| caution |
Cover the hose connection with
rags to prevent splash of fuel
that could be caused by some residual pressure
in the fuel pipe line.
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3.Assemble the special tool
called injector test set (MB992076) as shown in the
figure.
- Remove the mounting adapter for injector
and another adapter
on the hose end.
- To the hose ends from which each adapter is
removed, attach the special tool quick
connector (MB991990) and special tool hose adapter
(MB992001).
4.Attach the special tool between the main pipe
and high-pressure fuel hose.
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<Where the fuel pressure
gauge is used>
- Attach the fuel pressure gauge on the
special tool for measuring the fuel pressure via
an appropriate O-ring or gasket.
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<Where the fuel pressure
gauge set is used>
- Attach the special tool fuel pressure gauge
set (MB991981) on the special tool for measuring
the fuel pressure via an appropriate
gasket.
- Connect the leads from the fuel pressure
gauge set to the power supply (cigarette
lighter socket) and special tool vehicle
communication interface (V.C.I.)
(MB991824).
5.Connect the M.U.T.-III to the diagnosis
connector.
6.
| caution |
Connection and disconnection
of M.U.T.-III should be always
performed with the ignition switch turned to the
LOCK (OFF) position.
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Turn the ignition switch to the ON position. (But do
not start the engine.)
7.Select "Item No. 09" of
the M.U.T.-III actuator test to drive the fuel pump.Verify
there is no leakage from each section with the fuel pressure
being applied.
8.Finish the actuator test or turn
the ignition switch to the LOCK (OFF)
position.
9.Start the engine and run at
idle.
10.Measure the fuel pressure while the
engine is running at idle.
Standard value:
Approximately 324 kPa
11.Check to see that
fuel pressure at idle does not drop even after the engine
has been
raced several times.
12.If any of fuel pressure
measured in steps 10 and 11 is out of specification,
troubleshoot
and repair according to the table below.
Symptom
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Probable cause
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Remedy
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- Fuel pressure is
too low.
- Fuel pressure drops after
racing.
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Clogged
fuel filter
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Replace
the fuel filter.
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Fuel
leaking to the return side due to poor seating
of the fuel regulator valve
in the fuel pressure regulator or the settled
spring.
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Failed
fuel pressure regulator
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Low
fuel pump delivery pressure
|
Replace
fuel pump.
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Fuel
pressure is too high.
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Binding
valve in fuel pressure regulator
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Failed
fuel pressure regulator
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13.Stop the engine and check change of fuel
pressure gauge reading.Normal if the reading
does not drop within 2 minutes.If it does, observe the rate
of drop and troubleshoot and repair
according to the table below.
Symptom
|
Probable cause
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Remedy
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Fuel
pressure drops gradually after engine is
stopped
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Leaky
injector
|
Replace
injector.
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Leaky
fuel regulator valve seat
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Failed
fuel pressure regulator
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Fuel
pressure drops sharply immediately after engine
is stopped
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Check
valve in fuel pump is held open
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Replace
fuel pump.
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14.Release residual pressure from the fuel
pipe line.
15.Remove the special tool from main
pipe.
| caution |
Cover the hose connection with
rags to prevent splash of fuel
that could be caused by some residual pressure
in the fuel pipe line.
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16.Replace high-pressure fuel hose to main
pipe.
17.Check for any fuel leaks by following the
procedure in step 7.
18.Disconnect the
M.U.T.-III.
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