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1.Release residual pressure from the fuel pipe line to prevent fuel gush out. Reduce pressurized fuel lines (Refer to  ).
| 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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2.Remove the fuel high-pressure hose at the delivery pipe.
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3.Assemble the special tool called injector test set (MB992076) as shown in the figure according to the following procedure.
- Remove the injector installation adapter from the hose. Remove another hose together with the adapter and remove the adopter from the remaining hose.
- Install the special tool MB992049 (quick connector) and the special tool MB992001 (hose adapter) to the hose without the adapter.
- Remove the nipple of the bolt of the special tool MD998709 (adapter hose).
- Install the special tool prepared in the procedure "c" to the nipple that was removed together with hose in the procedure "a".
4.Install the special tool assembled in Step 3 between the delivery pipe and fuel high-pressure hose.
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<Where the fuel pressure gauge is used>
- Install 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>
- Install 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.
| 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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Connect the M.U.T.-III to the diagnosis connector.
6.Turn the ignition switch to the ON position. (But do not start the engine.)
7.Select "Item No. 9" from the M.U.T.-III actuator test to drive the fuel pump. Check that there are no fuel leaks from any parts.
8.Finish the actuator test or turn the ignition switch to "LOCK" (OFF) position.
9.Start the engine and run at idle.
10.Measure 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 return side due to poor fuel regulator valve seating or settled spring.
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Replace fuel pressure regulator
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Low fuel pump delivery pressure
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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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Replace 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
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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
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Replace injector
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Leaky fuel regulator valve seat
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Replace 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. Reduce pressurized fuel lines (Refer to ).
| 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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15.Remove the fuel pressure gauge and special tool from the delivery pipe.
16.Install the fuel high-pressure hose over the delivery 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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