Where is the ECM located on a 1991 Chevy Cavalier and would that be reason for it turning over but not starting?

In a 1991 Chevy Cavalier, the Engine Control Module (ECM) is typically located under the dashboard, on the passenger side. However, its exact location might vary slightly depending on the trim level and options. It's often secured to the firewall or under the carpet near the passenger's feet. You might need to remove some trim pieces to access it.

Could a faulty ECM prevent a car from starting while it cranks (turns over)? Yes, absolutely. The ECM is the "brain" of the engine. If it's malfunctioning, it might not be sending the correct signals to the fuel injectors, ignition system, or other components necessary to start the engine. Even though the starter is turning the engine over, without the ECM's commands, the engine won't fire.

Important Note: Before you start tearing apart your dashboard, consider other more likely causes for a crank-no-start condition:

* Dead battery: The most common reason. Test the battery voltage.

* Bad starter: While it's turning over, it might be weak or failing.

* Fuel pump: Is the fuel pump working? Listen for the pump's whine when you turn the key to the "on" position (before cranking).

* Distributor cap/rotor: (if equipped) Check for cracks or corrosion.

* Ignition coil: Test the coil for proper voltage output.

* Cranking sensor: A faulty Crankshaft Position Sensor (CKP sensor) can prevent the engine from starting, even if the starter cranks the engine.

* Fuel delivery issues: Check fuel pressure.

Diagnosing a crank-no-start condition requires a systematic approach. Start with the simplest and most common causes before moving on to more complex components like the ECM. A diagnostic scan tool can often pinpoint the problem quickly and efficiently, saving you a lot of time and effort.