Disconnect high pressure fuel hose at fuel delivery pipe. Remove throttle body bracket (if necessary). Connect fuel pressure gauge with adapter between fuel delivery pipe and high pressure hose. See Fig 1 .
Connect negative battery terminal. Connect battery voltage to fuel pump test terminal. See FUEL PUMP TEST TERMINAL LOCATION table. Ensure no fuel leaks are present. Disconnect battery voltage to fuel pump test terminal.

Fig 1: Installing Fuel Pressure Tester (Typical)
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Start engine and let idle. Measure fuel pressure with vacuum hose connected to fuel pressure regulator. Record fuel pressure reading. Disconnect and plug vacuum hose from fuel pressure regulator. Record fuel pressure reading. See FUEL PUMP PERFORMANCE table.
Check for fuel pressure in fuel return hose by gently pinching hose while increasing engine speed. If fuel volume is low, fuel pressure in return hose will not be felt. Increase engine speed to 2500-3000 RPM, 2-3 times. Return engine to idle. Fuel pressure should not drop when engine is returned to idle.
Turn ignition off. On all models except Precis, ensure fuel pressure reading does not decrease within 2 minutes. On Precis, fuel pressure reading should not decrease within 5 minutes. On all models, if a decrease is noted, monitor speed of decrease.
If fuel pressure is lower than specification, fuel pressure drops at idle after increasing engine speed to 2500-3000 RPM, or no fuel pressure in fuel return hose can be felt, check for clogged fuel filter, or faulty fuel pressure regulator or fuel pump.
If fuel pressure is higher than specification, check for a faulty fuel pressure regulator or plugged fuel return line. If fuel pressure does not change when vacuum hose to regulator is connected or disconnected, check for a leaking or clogged vacuum hose to fuel pressure regulator or faulty fuel pressure regulator.
If fuel pressure decreases suddenly after engine is stopped, check valve within fuel pump is not seated. Replace fuel pump. If fuel pressure drops slowly, fuel injector is leaking or fuel pressure regulator valve seat is leaking. Check for faulty fuel injector or fuel pressure regulator. Repair as necessary.

When fuel pressure test is complete, repeat fuel pressure release procedure before disconnecting fuel pressure gauge. Install new "O" ring at end of high pressure hose. Check for fuel leaks.

FUEL PUMP TEST TERMINAL LOCATION

Application	Wire Color	Location
1.5L	BLK/WHT	Center Of Firewall
1.6L	BLK/BLU	Center Of Firewall

FUEL PUMP PERFORMANCE

Application

⁽¹⁾ At Idle psi (kg/cm² )

⁽²⁾ At Idle psi (kg/cm² )

All Models

38 (2.6)

47-50 (3.3-3.5)

⁽¹⁾

With vacuum at pressure regulator.

⁽²⁾

Without vacuum at pressure regulator.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Pressure Testing

Use the Manual With the Right Hardware

When to See a Mechanic

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