How to Check Fuel Delivery in a Jeep Grand Cherokeeby Contributor; Updated November 07, 2017
How to Check Fuel Delivery in a Jeep Grand Cherokee. The Jeep Grand Cherokee is a mid-sized, "unibody" sport utility vehicle manufactured by Chrysler's Jeep division. The Grand Cherokee debuted in 1993 and has gone through several partial and complete redesigns. The Grand Cherokee V8 made both Car and Driver magazine's "Ten Best" list and Motor Trend magazine's Truck of the Year in 1993.
Release fuel system pressure in Jeep Grand Cherokee vehicles produced after 2003. Disconnect the fuel pump relay from the power distribution center. Start the vehicle and let it run until it stalls. Try to start it again until the engine no longer runs. Turn the vehicle off and disconnect the fuel injectors.
Attach one end of a jumper wire to an injector and the other to the positive battery terminal. Secure one end of a second jumper wire to the remaining free injector terminal. Touch the free end of the second jumper wire to the negative battery terminal for about three seconds. Disconnect the fuel rail coupling.
Disconnect the vacuum line from the fuel pump pressure regulator and check for fuel. There shouldn't be any fuel in the line. If there is, the engine problems are caused by a faulty fuel pump pressure regulator. If there is no fuel in the lines, reattach the vacuum line and continue with the fuel delivery diagnostic.
Twist off the fuel pressure test port cap and attach a pressure gauge to the fuel pressure valve. Reconnect the negative battery cable and start the engine. Disconnect the vacuum hose again and check the gauge. It needs to read between 44 and 54 pounds per square inch. High pressure readings indicate that the pressure regulator is malfunctioning. Low pressure readings indicate that the fuel filter is clogged or that the fuel pump needs to be replaced.
Remove the fuel filter to check for clogs on 2004 and earlier Grand Cherokee model years. Cut the engine, relieve system pressure and remove the negative battery cable again so its safe to remove the filter. Jeep Grand Cherokee models made in 2005 and later do not use a separate fuel filter.
Detach the fuel pressure, fuel return and supply lines from the filter. Undo the filter bolts and remove the filter.
Examine the filter for clogs and replace it with a new one if necessary. If there are no clogs, the fuel delivery problem is due to a faulty fuel pump.