How to Check the Fuel Pressure in a Jeep Libertyby Dan Ferrell
Testing the fuel-pump pressure output of your Jeep Liberty for possible problems can be tricky. Negative results from one or more tests may not necessarily indicate a bad pump. However, a close inspection will help you isolate a possible problem like fuel leaks on the lines and near the pump, bad line connections or an obstructed pump strainer inside the fuel tank.
Detach the injector cover from the top of the engine using a ratchet and socket.
Connect a fuel pressure gauge to the fuel-rail test port near the fuel injectors. This port resembles the air valve on your Jeep tires. Wrap a shop towel around the test port as you connect the gauge to absorb any fuel spill.
Turn the ignition key to the "On" position.
Position the gauge bleed hose inside a suitable glass container and then open the gauge valve to remove any air in the line and leave the valve open.
Plug a scan tool to the vehicle computer data link connector located under the dashboard on the driver side.
Follow the instructions on your scan tool manual and activate the fuel pump. Then close the fuel-gauge bleed valve.
Make sure there are no fuel leaks around the gauge connections and read the fuel pressure on the gauge dial.
Compare the pressure reading to the one listed on the vehicle service manual for your particular Liberty model. If your reading is different from the one specified by your vehicle manufacturer, go on to the next step.
Turn the ignition key "Off" and repeat steps 3 through 8. However, this time block the fuel return hose using a pair of hose pinch pliers. This will isolate the fuel pressure regulator from your test.
Compare your pressure reading to the one specified by your vehicle manufacturer. If your reading is correct, your fuel pressure regulator might be defective. If you are still getting a different reading, go on to the next step.
Connect the fuel pressure gauge directly to the fuel-pump output hose. This will help you isolate other possible trouble spots, like fuel lines, fuel filter and regulator.
Compare your reading to the manufacturer number. If you get the correct reading this time, troubleshoot the fuel lines, fuel filter and regulator to isolate the problem. However, if your reading is still different, closely examine the fuel pump and troubleshoot it, if necessary.
Items you will need
- Ratchet and socket
- Fuel pressure gauge
- Shop rag
- Small glass container
- Scan tool
- Hose pinch pliers, if necessary
- Jeep Liberty 2002 thru 2004 (Haynes Repair Manual); Len Taylor, Tim Imhoff and John H. Haynes; 2004
- Modern Automotive Technology; James E. Duffy; 2003
- Scott Olson/Getty Images News/Getty Images