1991 MITSUBISHI ECLIPSE fuel pump

FUEL SYSTEM - Troubleshooting
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FUEL SYSTEM - Service Adjustment Procedures 4.8L Engine>
RELEASE OF RESIDUAL
PRESSURE FROM HIGHPRESSURE FUEL HOSE
N14FGAE
MD998709
MD998742
IFUO157Make the following operations to release the pressure remain-
ing in fuel pipe line so that fuel will not flow out.
(1) Disconnect the fuel pump harness connector at the fuel
tank rear side.
(2) Start the engine and after it stops by itself, turn the ignition
switch to OFF.
(3) Disconnect the battery
(-) terminal.
(4) Connect the fuel pump harness connector.
FUEL PUMP OPERATION CHECK
Nl4FDAG(1) Set the ignition switch at OFF.
(2) Check that when the batten/ voltage is directly applied to
the fuel pump check terminal, the operating sound of the
pump can be heard.
NOTESince the fuel pump is installed in the fuel tank, its
operating sound cannot be readily heard. Remove the fuel
tank cap and listen to the operating sound through the filler
port.(3) Hold the high pressure fuel hose between your fingers and
check that the fuel pressure can be felt.
FUEL PRESSURE TEST
Nl4FNAN(1) Reduce the fuel pressure in the fuel line.
(2) Disconnect the high pressure fuel hose from the delivery
pipe.
CautionCover the hose connection with shop towel to prevent
splash of fuel that could be caused by residual pressurein the fuel pipe line.
(3) Connect a fuel pressure gauge to the special tool (hose
adapter).Use a suitable O-ring or gasket between the fuel pressure
gauge and the special tool so as to seal in order to preventfuel leakage at this time.
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FUEL SYSTEM - Service Adjustment Procedures 4.8L Engine>14-45(4) Install the special tool, which was set in place in step
(3),
between the delivery pipe and the high pressure fuel hose.(5) Connect the
0 terminal of the batten/.
(6) Apply battery voltage to the fuel pump check terminal and
activate the fuel pump; then, with fuel pressure thus
applied, check to be sure that there is no fuel leakage fromthe pressure gauge or the special tool connection part.
(7) Start the engine and run at curb idle speed.
(8) Disconnect the vacuum hose form the pressure regulator
and clog the vacuum hose end. Measure the fuel pressure.Standard value:
330-350 kPa (47-50 psi) at curb idle
(9) Measure the fuel pressure when the vacuum hose is
connected to the pressure regulator:
Standard value: Approx. 270
kPa (38 psi) at curb idle
(10)Race the engine repeatedly in two or three series. Then
check that the fuel pressure does not fall when the engine
is running at idle.
(11)Check to be sure that there is fuel pressure in the return
hose also (by gently pressing the fuel return hose with a
finger while repeatedly racing the engine).
NOTEThere will be no fuel pressure in the return hose when the
volume of fuel flow is not sufficient.
(12)lf the results of the measurements made in steps (8) and
(9) above are not within the standard value, use the table
below to determine the probable cause, and then make the
necessan/ repair.

14-46FUEL SYSTEM - Service Adjustment Procedures <1.8L Engine>
Condition
Fuel pressure too low
Fuel pressure too highProbable causea. Clogged fuel filter
b. Fuel leaking toward return port due to
Remedy
a. Replace fuel filter.
improper seating of valve in fuel pressure
b. Replace fuel pressure regulator.
regulatorc. Low delivery pressure of fuel pump
c. Replace fuel pump.
a. Stuck valve in fuel pressurea. Replace fuel pressure regulator.
regulator
b. Clogged or bent fuel return hose or pipeb. Repair or replace hose or pipe.
‘.
Fuel pressure witha. Clogged or broken vacuum hose or nipple
a. Repair or replace the vacuum hose or
vacuum hose connectednipple.
not different from fuel
pressure with vacuum
b. Stuck valve in fuel pressure regulator orb. Replace fuel pressure regulator.
hose not connecteddefective valve seating
(13)Stop the engine and check for change in fuel pressure
gauge indication, which should not drop.
If the gauge indication drops, observe the rate of drop and
determine and remove the causes according to the
following table.
ConditionProbable causeRemedy
Fuel pressure dropsLeakage from injectorReplace injector.
slowly after engine is
stopped.
rqFuel pressure drops im-Check valve in fuel pump does not closeReplace fuel pump.
mediately after engine is
stooped.
(14)Reduce the fuel pressure in the fuel line.
(16)Disconnect the high pressure fuel hose and remove the
fuel pressure gauge from the delivery pipe.
Caution
Cover the hose connection with shop tdwel to prevent
splash of fuel that could be caused by residual pressure
in the fuel pipe line.
(16)Mount a new O-ring in the groove at the end of the high
pressure fuel hose.
(17)Connect the high pressure fuel hose to the delivery pipe,
and tighten the screws to the specified torque.
(18)Check for fuel leaks.
@ Apply battery voltage to the fuel pump check terminal
to operate the fuel pump.
@ With fuel pressure acting, check the fuel line for leaks.
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FUEL SYSTEM - Service Adjustment Procedures <1.8L Engine>14-47
A
E3x>
/ )Engine speed
(rpm)1 FU446Engine speed (rpm)
>3FU262EGR VALVE CONTROL VACUUM CHECK

Check ConditionEngine coolant temperature: 85-‘95”C (185-205°F)
(1) Disconnect the vacuum hose from the throttle body EGR
vacuum nipple and connect a hand vacuum pump to the
nipple.(2) Start the engine and check to see that, after raising the
engine speed by racing the engine, vacuum raises pro-
portionately with the rise in engine speed.
NOTEIf there is a problem with the change in vacuum, it is
possible that the throttle body port may be clogged and
require cleaning.
PURGE PORT VACUUM CHECKCheck ConditionN14FvBcEngine coolant temperature:
85-95°C (185-205°F)
(1) Disconnect the vacuum hose from the throttle body purge
hose nipple and connect a hand vacuum pump to the
nipple.(2) Start the engine and check to see that, after raising the
engine speed by racing the engine, vacuum remains fairly
constant.NOTE
If there is no vacuum created, it is possible that the throttlebody port may be clogged and require cleaning.

FUEL SYSTEM - Service Adjustment Procedures <2.0L Engine>14-51THROTTLE BODY (THROTTLE VALVE AREA)
CLEANINGNl4FtU
(1) Warm up the engine, then stop it.
(2) Remove the air intake hose from the throttle body.
(3) Plug the bypass passage inlet of the throttle body.
CautionDo not allow cleaning solvent to enter the bypass
passage.(4) Spray cleaning solvent into the valve through the throttle
body intake port and leave it for about 5 minutes.
(5) Start the engine, race it several times and idle it for about 1minute. If the idling speed becomes unstable (or if the
engine stalls), slightly open the throttle valve to keep the
engine running.
(6) If the throttle valve deposits are not removed, repeat steps
(4) and (5).
(7) Unplug the bypass passage inlet.
(8) Attach the air intake hose.
(9) Disconnect the battery terminal for 10 seconds or more,
and then reconnect it.
(lO)Adjust the basic idle speed. (Refer to P.14-48.)
RELEASE OF RESIDUAL PRESSURE FROM HIGH
PRESSURE FUEL HOSE
N14FGAFRefer to
P.14-44.FUEL PUMP OPERATION CHECK
N14FDAG(1) Set the ignition switch at OFF.
(2) Check that when the battery voltage is directly applied to
the fuel pump check terminal, the operating sound of the
pump can be heard.
NOTESince the high pressure fuel pump is installed in the fuel
tank, its operating sound cannot be readily heard. Remove
the fuel tank cap and listen to the operating sound through
the filler port.
I(3) Hold the high pressure fuel hose between your fingers and
check that the fuel pressure can be felt.

FUEL SYSTEM - Service Adjustment Procedures <2.0L Enaine>14-53
MD998709
MD998742
I
FU01571-(4) Connect a fuel pressure gauge to the special tool (hose
adapter).Use a suitable O-ring or gasket between the fuel-pressure
gauge and the special tool so as to seal in order to preventfuel leakage at this time.
(5) Install the special tool, which was set in place in step
(4),
between the delivery pipe and the high-pressure fuel hose.(6) Connect the
0 terminal of the battery.
(7) Apply battery voltage to the fuel pump check terminal and
activate the fuel pump; then, with fuel pressure thus
applied, check to be sure that there is no fuel leakage fromthe pressure gauge or the special tool connection part.
(8) Start the engine and run at curb idle speed.
(9) Disconnect the vacuum hose from the pressure regulator
and clog the vacuum hose end. Measure the fuel pressure.Standard value:
Turbo>330-350 kPa (47-50 psi) at curb idle

250-270 kPa (36-38 psi) at curb idle

290-320 kPa (41-46 psi) at curb idle
(10)Measure the fuel pressure when the vacuum hose is
connected to the pressure regulator:
Standard value:
Approx. 270
kPa (38 psi) at curb idle
Approx.
190 kPa (27 psi) at curb idle
Approx. 230
kPa (33 psi) at curb idle

14-54FUEL SYSTEM - Service Adjustment Procedures <2.0L Engine>
(11)Race the engine repeatedly in two or three series. Then
check that the fuel pressure does not fall when the engine
is running at idle.
(12)Check to be sure that there is fuel pressure in the return
hose also (by gently pressing the fuel return hose with a
finger while repeatedly racing the engine).
NOTEThere will be no fuel pressure in the return hose when the
volume of fuel flow is not sufficient.
(13)lf the results of the measurements made in steps (9) and
(10) above are not within the standard value, use the table
below to determine the probable cause, and then make the
necessary repair.
Condition
Fuel pressure too lowProbable causeRemedy
a. Clogged fuel filtera. Replace fuel filter.
b. Fuel leaking toward return port due tob. Replace fuel pressure regulator.
improper seating of valve in fuel pressure
regulator
c. Low delivery pressure of fuel pumpc. Replace fuel pump.
Fuel pressure too higha. Stuck valve in fuel pressure
a. Replace fuel pressure regulator.regulator
b. Clogged or bent fuel return hose or pipeb. Repair or replace hose or pipe.
Fuel pressure witha. Clogged or broken vacuum hose or nipplea. Repair or replace vacuum hose or
vacuum hose connected
nipple.
not different from fuel
pressure with vacuumb. Stuck valve in fuel pressure regulator or
b. Replace fuel pressure regulator.
hose not connecteddefective valve seating
(14)Stop the engine and check for change in fuel pressure
gauge indication, which should not drop.
If the gauge indication drops, observe the rate of drop and
determine and remove the causes according to the
following table.
Condition
Fuel pressure drops
slowly after engine is
stopped.Probable cause
Leakage from injectorRemedy
Replace injector.
Fuel pressure drops
im-Check valve in fuel pump does not closeReplace fuel pump.
mediately after engine is
stopped.
(15)Reduce the fuel pressure in the fuel line.
(16)Disconnect the high pressure fuel hose and remove the
fuel-pressure gauge from the delivery pipe.
Caution
Cover the hose connection with shop towel to prevent
splash of fuel that could be caused by residual pressurein the fuel pipe line.
(17)Mount a new O-ring in the groove at the end of the high
pressure fuel hose.