1. Verify Fuel Pump Installation and Operation:
* Double-check connections: Ensure all electrical connections to the fuel pump are secure and correctly wired. A loose or corroded connection is a common culprit. Pay close attention to the power and ground wires.
* Listen for the pump: Turn the ignition key to the "ON" position (without cranking the engine). You should hear a brief whirring sound from the fuel pump in the fuel tank. If you don't hear it, the pump may be faulty (even a new one can be defective) or there's an electrical problem. If you hear the pump briefly, but it then stops, you might have a relay problem.
* Fuel pressure test: This is crucial. You need a fuel pressure gauge to check the pressure at the fuel rail. The specification for your Jeep's fuel pressure is available in your repair manual or online (search for "1998 Jeep Grand Cherokee fuel pressure"). Low or no pressure indicates a problem beyond just the pump itself. A bad fuel pressure regulator or clogged fuel filter could be to blame.
* Check the fuel pump relay: Locate the fuel pump relay (consult your repair manual for its location) and swap it with a known good relay of the same type. This will rule out a faulty relay.
2. Beyond the Fuel Pump:
* Cranking System: Is the engine turning over when you try to start it? If not, you have a problem with the battery, starter, or related components.
* Ignition System: A faulty ignition coil, distributor (if equipped), crankshaft position sensor, or camshaft position sensor can prevent the engine from starting even with fuel.
* Fuel Filter: A clogged fuel filter restricts fuel flow, even if the pump is working. Replace it if it's old or you suspect a clog.
* Computer Issues: A faulty PCM (Powertrain Control Module) or other computer issues can affect fuel delivery. This is less likely, but possible. A diagnostic scan tool is needed to check for codes.
* Security System: If your Jeep has an aftermarket alarm or immobilizer system, it might be preventing the engine from starting.
3. Systematic Approach (Recommended):
1. Listen for the fuel pump: (As described above)
2. Fuel pressure test: (Most important next step)
3. Check the fuel pump relay: (Easy to do)
4. Inspect the fuel filter: (Could be a simple fix)
5. Verify battery and starter: (Ensure the engine turns over)
6. Check ignition components: (If everything else checks out)
7. OBDII scan: (Check for diagnostic trouble codes)
Important Considerations:
* Repair Manual: A repair manual specific to your 1998 Jeep Grand Cherokee is invaluable. It provides diagrams, specifications, and troubleshooting steps.
* Professional Help: If you're not comfortable working on your vehicle's fuel system, take it to a qualified mechanic. Working with fuel systems requires care and safety precautions.
By systematically checking these items, you'll significantly increase your chances of identifying why your Jeep won't start, even after replacing the fuel pump. Remember safety first! Gasoline is flammable.
