* Crank sensor: A faulty crankshaft position sensor (CKP sensor) prevents the engine control module (ECM) from knowing the crankshaft's position, thus preventing proper timing of fuel injection and spark. Starting fluid works because it's independent of the sensor's signal, but the car won't run consistently without a functioning sensor.
* Cam sensor: Similar to the crank sensor, a faulty camshaft position sensor (CMP sensor) prevents the ECM from knowing the camshaft's position, crucial for valve timing.
* ECM/PCM: The engine control module (also called the powertrain control module, or PCM) could be faulty. While it's less common, a malfunctioning ECM can prevent the engine from starting even with fuel and spark.
* Compression: Low compression in one or more cylinders will prevent the engine from starting. Starting fluid might provide a brief burst of power, but sustained running requires proper compression to ignite the fuel/air mixture. A compression test is needed to confirm this.
* Timing: While you have spark, the timing could be significantly off, preventing proper ignition. This often points to a timing chain or belt issue, or a problem with the timing components themselves.
* Wiring or Connections: A faulty wire or loose connection in the ignition system, fuel system, or sensor circuits could disrupt the signal flow. It's worth carefully checking all connections and wiring harnesses.
What to do next:
1. Get a professional scan: Take the car to a mechanic who can read diagnostic trouble codes (DTCs) from the ECM. This is the most efficient way to pinpoint the problem.
2. Compression Test: A compression test is crucial to rule out low compression as the cause.
3. Check for codes: Some auto parts stores can perform a basic scan for codes for free.
Simply having fuel pressure and spark doesn't guarantee a starting engine. The timing and coordination of these elements are vital, and the ECM plays a critical role. A proper diagnostic scan is the best first step.
