* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the engine's rotational position. A faulty CKP sensor will prevent the engine from starting or running smoothly, often causing it to die while driving. This is a common culprit in older vehicles.
* Cam Position Sensor (CMP Sensor): Similar to the CKP sensor, a faulty CMP sensor prevents the engine from starting. It's crucial for timing the fuel injection and ignition.
* Ignition System Problems: This could include:
* Ignition Coil: A failing ignition coil can prevent spark to one or more cylinders.
* Ignition Module: This controls the ignition coils. A faulty module can cause similar issues.
* Spark Plugs and Wires: Worn or damaged spark plugs or wires can interrupt the spark. Check for corrosion, cracks, or gaps that are out of spec.
* Mass Airflow Sensor (MAF Sensor): A dirty or faulty MAF sensor provides inaccurate readings of air entering the engine, leading to poor performance and stalling.
* Throttle Position Sensor (TPS): A faulty TPS sensor gives the computer inaccurate information about the throttle position, affecting fuel delivery and potentially causing stalling.
* Computer/ECM Problems: Though less common, a problem with the Engine Control Module (ECM) itself can cause a variety of issues, including stalling.
* Wiring Issues: A short circuit or damaged wiring harness anywhere in the ignition, fuel, or sensor circuits could cause intermittent or complete failure.
* Fuel Pressure Regulator: While you changed the pump, a faulty fuel pressure regulator could still be preventing adequate fuel pressure.
* Security System: If your Ranger has an aftermarket or factory alarm system, a malfunctioning system could be preventing the vehicle from starting.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any stored codes from the vehicle's computer. This is the *most important* first step. These codes will point you toward the most likely culprit.
2. Visual Inspection: Carefully examine all wiring related to the fuel system, ignition system, and sensors for any signs of damage, corrosion, or loose connections.
3. Check Fuel Pressure: Even with a new pump, verify that you have adequate fuel pressure. This usually requires a fuel pressure gauge.
4. Test Sensors: If you have a multimeter, you can test the CKP, CMP, MAF, and TPS sensors to see if they are producing the correct signals. However, this often requires specific knowledge of sensor operation and testing procedures.
Recommendation: Start with an OBD-II scan. This will give you valuable information to guide your troubleshooting efforts. If you're not comfortable working on your vehicle's electrical system, it's best to take it to a qualified mechanic. Attempting repairs without the proper knowledge and tools can lead to further damage.
