* Crankshaft Position Sensor (CKP): This sensor is crucial. It tells the computer the crankshaft's position to time the ignition correctly. A faulty CKP sensor prevents the engine from firing, even with spark. This is a very common culprit for no-start conditions where the engine cranks.
* Camshaft Position Sensor (CMP): Similar to the CKP sensor, the CMP sensor tells the computer the camshaft's position. A faulty CMP sensor can also prevent the engine from firing. The severity of the failure can vary.
* Fuel Pump: While the starting fluid test suggested a fuel problem is unlikely, the pump itself might be weak or failing entirely. The fluid helps bypass the pump momentarily, causing a temporary start. Check fuel pressure at the fuel rail. This requires a fuel pressure gauge.
* Fuel Pump Relay or Fuse: The pump may be getting power intermittently. Check the relay and fuse for the fuel pump. A simple swap with a known good relay is a quick test.
* Ignition Switch: While less likely given you've already replaced components, a failing ignition switch might not be sending sufficient power to the system.
* Computer (PCM): Although rare, a faulty PCM (Powertrain Control Module) can cause a no-start condition. This is harder to diagnose and usually requires professional help.
Troubleshooting Steps:
1. Check Fuel Pressure: This is the most important next step. Rent or borrow a fuel pressure gauge and check the pressure at the fuel rail. The specification for your engine should be readily available online. Low or no pressure confirms a fuel delivery problem.
2. Check for Spark at the Plugs: Even though you've replaced ignition components, verify you're getting spark at each spark plug. A weak spark could still be an issue even with new parts. Use a spark tester or carefully check for spark with a grounded plug wire and a gap to a grounded metal surface. Avoid touching the spark plug while it's in this position.
3. Check CKP and CMP Sensors: If possible, check these sensors for codes using an OBD-II scanner. You can also test for continuity, but this typically requires a multimeter and some technical knowledge. Visual inspection for obvious damage is a starting point.
4. Inspect Wiring and Connectors: Check for any corroded, damaged, or loose wiring, especially in the area of the sensors and ignition system.
5. Test the Fuel Pump Relay and Fuse: Use the steps mentioned above.
If you're not comfortable working on your vehicle's electrical system, it's best to take it to a mechanic. Incorrect diagnosis can lead to further damage. The cost of a professional diagnosis is likely less than the cost of replacing numerous parts without knowing the actual problem.
