Signs the Fuel Pump Is Going Out on a 98 Jeep Grand Cherokee Limited

Among all the Native American tribes, five are known as “The Civilized Tribes.” The Civilized Tribes were so-called by the Europeans because they’d maintained good relations with them, and been willing to adopt their cultures. Even so, The Cherokee tribe was probably the only one of the Five to never lose itself in the culture of the Anglo invaders, adapting to the new but never becoming so “civilized” that it lost its own. The Jeep that bore this tribe’s name was much the same, adapting to the needs of its time and the culture around it, while never forgetting the rugged spirit of its forebears.
Test Drive
This generation of Cherokee used a return-style fuel system with an electric pump and an external pressure regulator. With this style of fuel system, failure is usually quicker than usual from the time the truck starts acting up till the time it dies completely. Your first sign of a loss of fuel pressure will be a distinct stumble when first accelerating, gradually becoming consistent hesitation and power loss. The Jeep will eventually lose its ability to rev to high rpm, falling to a rough idle before dying completely. Or, the pump may suddenly fail, and the Jeep will stall as though it ran out of gas. Speaking of which: Make sure you’ve got at least half a tank before testing.
First Check — The Sound of Silence
Before anything else, park the Jeep and open the gas cap. have an assistant turn the key to the “on” position without attempting to start the engine for five seconds. Turn it off for three, then on for five, and repeat again. Listen at the gas filler; you should hear the fuel pump hum to life when the ignition is turned on. If you heard nothing, then go to the main fuse block under the hood, and locate the fuel pump relay. Take a long screwdriver, firmly press the tip on the pump relay, and wedge the end of the handle securely into your ear. Have your assistant turn the ignition on and off again. You should hear the relay click on and off. If you don’t hear it click, the relay is bad.
Under Pressure
Hearing the pump turn on only means that it’s on and the relay is working — that doesn’t mean it’s developing the right amount of pressure. Locate the Schrader valve on the fuel rail on the manifold; it looks like one of your tire valve stems with the cap on. Unscrew the cap, and connect a fuel pressure gauge capable of reading at least 60 psi to the valve. Start the engine if it will start, which it should as long as the pump is at least running. You should see a steady 31 psi of fuel pressure at idle. Identify the fuel pressure regulator on the fuel rail, and pull the vacuum line off the regulator. Plug the line with a screw or golf tee. You should see fuel pressure at idle rise by 8 to 10 psi. If it doesn’t rise to 39 to 41 psi, replace the fuel pressure regulator. If it exceeds 45 psi, check the return line for kinks and obstructions.
Final Diagnosis
To confirm that you have a pressure-supply problem after ruling out the pressure regulator, disconnect the vacuum line at the regulator, and hit the throttle quickly. If, while you hit the throttle, the engine bogs down and the fuel pressure drops precipitously, you have a problem with low supply pressure. At this point, you’ve narrowed it down to either the fuel filter or the pump. A clogged filter will generally force pressure to drop very low when you hit the throttle, and slowly creep back up when you release the throttle and drop back to idle. But it should eventually return to normal, which is 31 psi with the vacuum line connected, or 39 to 41 with it disconnected. A bad pump will tend to fluctuate a bit more, and remain lower than normal even at idle. Either way, plans on replacing the fuel filter, even if only for maintenance. Retest the fuel pressure; if it’s still low, replace the pump.





Leave a Reply

Your email address will not be published. Required fields are marked *