NOTE: If scan tool is not available use following procedure to operate fuel pump On. Remove fuel pump relay from underhood fuse/relay box. Using fused jumper, jumper fuel pump relay socket cavities No. 1 and 5. See Fig 1 .

Turn ignition off. Ensure A/C is off (if equipped). Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE . Install Fuel Pressure Gauge Set (J-34730-1) or equivalent to fuel rail or fuel supply line. Install fuel pump relay. Connect Tech 2 or equivalent scan tool to Data Link Connector (DLC). DLC is located under small cover on left side of dash. Turn ignition on. Using scan tool, command fuel pump On. Observe fuel pressure gauge. Fuel pressure on all models should be 42-55 psi (290-376 kPa). If fuel pressure is not as specified, see appropriate FUEL SYSTEM DIAGNOSIS procedure. If fuel pressure is as specified, testing is complete.
Start engine let fuel pressure build to maximum pressure. Observe fuel pressure gauge. When engine is running, fuel system pressure should drop 3-15 psi (21-105 kPa) from engine off fuel pump running specification. If pressure does not drop as specified, see appropriate FUEL SYSTEM DIAGNOSIS procedure. If fuel pressure drops as specified, testing is complete.

Fig 1: Jumping Fuel Pump Relay

Courtesy of ISUZU MOTOR CO.

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

Fuel Pump Pressure Test

Use the Manual With the Right Hardware

When to See a Mechanic

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