Possible Causes:
* Faulty PCM (Powertrain Control Module): The PCM is the "brain" of your Jeep's engine and controls many functions, including fuel delivery, gauge readings, and the airbag system. A failing PCM can cause erratic behavior across multiple systems. This is a serious possibility given the wide range of issues.
* Faulty Crankshaft Position Sensor (CKP): This sensor tells the PCM the position of the crankshaft, crucial for proper ignition timing and fuel injection. A bad CKP sensor can prevent the engine from starting and cause erratic gauge readings.
* Faulty Fuel Pump or Relay: The intermittent fuel supply points strongly to a problem with the fuel pump itself, the fuel pump relay, or wiring to the pump. The fuel pump might be weak or intermittently failing.
* Bad Battery or Alternator: While less likely given the other symptoms, a weak battery or alternator could contribute to erratic electrical issues and starting problems. A low voltage could affect the PCM's operation.
* Wiring Issues: Corrosion, damaged wires, or loose connections anywhere in the electrical system could cause intermittent problems across multiple systems. This is particularly relevant given the seemingly random nature of the issues.
* Ignition Switch: A failing ignition switch can affect power to various systems and prevent starting.
* Security System Issues: Some vehicles have immobilizers that prevent starting if a problem is detected with the key or system.
Troubleshooting Steps (in order of likelihood and safety):
1. Check the Battery and Alternator: Have the battery voltage tested at both idle and with the engine running. A low voltage reading points to a bad battery or alternator.
2. Inspect Wiring and Connections: Look for any obvious corrosion, damage, or loose connections, particularly around the PCM, fuel pump relay, and battery terminals.
3. Check Fuel Pump Relay: Locate the fuel pump relay (consult your Jeep's repair manual) and try swapping it with a known good relay of the same type (if possible). Listen carefully for the fuel pump to prime when you turn the key to the "on" position.
4. Check Fuel Pressure: This requires a fuel pressure gauge and might necessitate some mechanical expertise. Low or inconsistent fuel pressure confirms a problem with the fuel pump or system.
5. Diagnose with an OBD-II Scanner: A code reader can retrieve diagnostic trouble codes (DTCs) stored in the PCM. These codes can provide valuable clues to the underlying problem. Focus particularly on codes related to fuel system, crankshaft sensor, or other relevant components.
6. Consider Professional Diagnosis: Given the complexity of the symptoms, a professional mechanic with experience in older Jeeps is likely the best approach. They have the diagnostic tools and expertise to pinpoint the problem more effectively.
Safety Note: Working on a car's electrical system or fuel system can be dangerous. If you're not comfortable with automotive repair, seek professional help. A faulty PCM is a complex problem best handled by a skilled mechanic.
