Mitsubishi Eclipse. Manual - part 646

FUEL SUPPLY DIAGNOSIS

TSB Revision

FUEL SUPPLY

13C-5

STEP 2. Check the fuel pressure.
(1) Release residual pressure from the fuel line to prevent fuel 

spray. <2.4L> (Refer to 

P.13A-932

.) <3.0L> (Refer to 

P.13B-1109

.)

WARNING

To prevent a fire, cover the hose connection with 
shop towels to prevent splashing of fuel that could be 
caused by some residual pressure in the fuel pipe 
line.

(2) Disconnect the fuel high-pressure hose at the fuel rail side.
(3) Assemble the fuel pressure measurement tools as follows.
(4) When using the fuel pressure gauge

a. Remove the union joint and bolt from special tool 

MD998709 (adaptor hose) and instead attach special 
tool MD998742 (hose adaptor) to the adaptor hose.

b. Place a suitable O-ring or gasket on assembled special 

tools MD998709 and MD998742 and install the fuel 
pressure gauge.

c. Install the assembled fuel pressure measurement tools 

between the fuel rail and fuel high-pressure hose.

(5) When using the special tool MB991637 (fuel pressure 

gauge set)
a. Remove the union joint and bolt from special tool 

MD998709 (adaptor hose) and instead attach special 
tool MD998742 (hose adaptor) to the adaptor hose.

b. Install special tool MB991637 (fuel pressure gauge set) 

to assembled special tools MD998709 and MD998742 
via a gasket.

c. Install the assembled fuel pressure measurement tools 

between the fuel rail and the fuel high-pressure hose.

AC210685

FUEL PRESSURE
GAUGE

AB

O-RING OR GASKET

MD998709

MD998742

FUEL
RAIL

FUEL
HIGH-PRESSURE
HOSE

AC210686

MB991637

AB

O-RING OR GASKET

MD998709

MD998742

FUEL
RAIL

FUEL
HIGH-PRESSURE
HOSE

FUEL SUPPLY DIAGNOSIS

TSB Revision

FUEL SUPPLY

13C-6

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(6) Connect scan tool MB991958 to the data link connector.
(7) Use the Actuator test 07 to drive the fuel pump. Check that 

there is no fuel leaking from any section when the fuel 
pump is operating.

(8) Stop the fuel pump.
(9) Start the engine and run at idle.
(10)Measure fuel pressure while the engine is running at idle.

Standard value: Approximately 270 kPa (38 psi) at 
curb idle

(11)Disconnect the vacuum hose from the fuel pressure 

regulator and measure fuel pressure with the hose end 
closed with your finger.

Standard value: 330 

− 350 kPa (47 − 50 psi) at curb 

idle

(12)Check to see that fuel pressure at idle does not drop even 

after the engine has been revved several times.

(13)Revving the engine repeatedly, hold the fuel return hose 

lightly with your fingers to feel that fuel pressure is present 
in the return hose.
NOTE: If the fuel flow rate is low, there will be no fuel pres-
sure in the return hose.

(14)If any of fuel pressure measured in steps 8 to 11 is out of 

specification, troubleshoot and repair according to the table 
below.

AC303127

AB

MB991911

16-PIN

MB991827

MB991824 

AC106099AB

<2.4L>

AC106100

<3.0L>

AB

SYMPTOM

PROBABLE CAUSE

REMEDY

• Fuel pressure too low

• Fuel pressure drops after racing

• No fuel pressure in fuel return 

hose

Clogged fuel filter

Replace fuel filter

Fuel leaking to return side due to 
poor fuel regulator valve seating or 
settled spring

Replace fuel pressure regulator

Low fuel pump delivery pressure

Replace fuel pump

FUEL SUPPLY DIAGNOSIS

TSB Revision

FUEL SUPPLY

13C-7

(15)Stop the engine and observe fuel pressure gauge reading. 

It is normal if the reading does not drop within two minutes. 
If it does, observe the rate of drop and troubleshoot and 
repair according to the table below. Start, then stop the 
engine.
a. Squeeze the fuel return line closed to confirm leak-down 

occurs from defective fuel pressure regulator.

b. Squeeze the fuel supply line closed to confirm 

leak-down occurs from defective fuel pump check valve.

c. If pressure continues to drop with both fuel lines 

squeezed closed, injector(s) are leaking.

(16)Release residual pressure from the fuel pipe line. <2.4L> 

(Refer to 

P.13A-932

.) <3.0L> (Refer to 

P.13B-1109

.)

WARNING

Cover the hose connection with shop towels to pre-
vent splash of fuel that could be caused by some 
residual pressure in the fuel pipe line.

(17)Remove the fuel pressure gauge or special tool 

MB991637, and special tools MD998709 and MD998742 
from the fuel rail.

(18)Replace the O-ring at the end of the fuel high-pressure 

hose with a new one.

(19)Fit the fuel high-pressure hose into the fuel rail and tighten 

the bolts to specified torque.

Tightening torque: 4.9 

± 1.0 N⋅m (44 ± 8 in-lb)

(20)Check for fuel leaks.

a. Use scan tool MB991958 to operate the fuel pump.
b. Check the fuel line for leaks, and repair as needed.

(21)Disconnect scan tool MB991958.
Q: Is the fuel pressure test in good condition?

YES : Go to Step 5.
NO :  Repair or replace. Then go to Step 3.

Fuel pressure too high

Binding valve in fuel pressure 
regulator

Replace fuel pressure regulator

Clogged fuel return hose or pipe

Clean or replace hose or pipe

Same fuel pressure when vacuum 
hose is connected and when 
disconnected

Damaged vacuum hose or 
clogged nipple

Replace vacuum hose or clean 
nipple

Defective fuel pressure regulator

Replace fuel pressure regulator

SYMPTOM

PROBABLE CAUSE

REMEDY

SYMPTOM

PROBABLE CAUSE

REMEDY

Fuel pressure drops gradually 
after engine is stopped

Leaky injector

Replace injector

Leaky fuel regulator valve seat

Replace fuel pressure regulator

Fuel pressure drops sharply 
immediately after engine is 
stopped

Check valve in fuel pump is held 
open

Replace fuel pump

AC106598

FUEL HIGH-
PRESSURE
HOSE

MD998709

MD998742

FUEL RAIL

AB

FUEL SUPPLY DIAGNOSIS

TSB Revision

FUEL SUPPLY

13C-8

STEP 3. Check for bending, twisting or clogging of the fuel 
pipe or hose.
Q: Are the fuel pipe and hose in good condition?

YES : Go to Step 4.
NO :  Repair or replace. Then go to Step 6.

STEP 4. Check the fuel pump module operation.

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958. 
(1) Check the operating of the fuel pump by using scan tool 

MB991958 to force-drive the fuel pump.

(2) If the fuel pump will not operate, check by using the 

following procedure. If normal, check the fuel pump drive 
circuit.
a. Turn the ignition switch to the "LOCK" (OFF) position.
b. Remove the fuel pump relay, and apply battery voltage 

to harness-side connector terminal number 2. Check 
that an operating sound can be heard from the fuel 
pump.

NOTE: As the fuel pump is an in-tank type, the fuel 
pump sound is hard to hear. Remove the fuel tank 
filler tube cap and check from the tank inlet.

c. Check for fuel pressure by pinching the fuel hose with 

fingertips.

d. Install the fuel pump relay.

Q: Is the fuel pump module operation in good condition?

YES : Then go to Step 5.
NO :  Replace. Then go to Step 6.

AC303127

AB

MB991911

16-PIN

MB991827

MB991824 

AC000230

FUEL PUMP RELAY

AB