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Home >> Jeep >> 2003 >> Grand Cherokee Overland >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Fuel Systems >> Fuel Pressure Leak Down Test >> Liberty & Wrangler

Liberty & Wrangler

  1. Remove air cleaner housing (if necessary) to access fuel supply line at fuel rail. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE  . Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. See Figure .
  2. Install a 0-60 psi (0-4.2 kg/cm2 ) fuel pressure gauge at test port on fuel line pressure test adapter hose. Start engine and bring to normal operating temperature. Observe test gauge. Normal operating pressure should be 44.2-54.2 psi (3.1-3.7 kg/cm2 ). Turn ignition off.
  3. Pressure should not fall below 30 psi for 5 minutes. If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the fuel pump module, or a fuel tube/line is leaking. Again, start engine and bring to normal operating temperature. Turn ignition off.
  4. This test step checks for fuel injector or fuel rail leakage. Clamp off the rubber hose portion of fuel line pressure test adapter hose between the fuel rail and the test port "T" on fuel line pressure test adapter hose. If pressure now holds at or above 30 psi, a fuel injector or the fuel rail is leaking. Repair as necessary and retest. If pressure still falls below 30 psi, go to next step.
  5. This step checks the fuel pump check valve, filter, regulator check valve and fuel tube/line for leakage. Clamp off the rubber hose portion of fuel line pressure test adapter hose between the vehicle fuel line and test port "T" on fuel line pressure test adapter hose. If pressure now holds at or above 30 psi, a leak may be found at a fuel tube/line. Repair as necessary and retest. If no leaks are found at fuel tubes or lines, one of the check valves in either the electric fuel pump, fuel filter or fuel pressure regulator (Liberty), fuel filter/pressure regulator (Wrangler) may be leaking. A quick loss of pressure usually indicates a defective check valve in the pressure regulator. A slow loss of pressure usually indicates a defective check valve in the bottom of the fuel pump module. The check valves are not serviced separately. Also, the electric fuel pump is not serviced separately. Replace fuel pump module as necessary. See FUEL PUMP MODULE under FUEL SYSTEMS in appropriate REMOVAL & INSTALLATION article.
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