* Ignition Switch: The ignition switch itself could be faulty. It's responsible for sending power to the starter circuit. A worn or broken switch won't allow the starter to engage.
* Neutral Safety Switch (NSS): This switch prevents the car from starting unless it's in Park or Neutral. A faulty NSS won't allow power to reach the starter, even if the key is turned. This is a very common problem on older cars.
* Wiring Issues: There could be a break or short in the wiring between the ignition switch, NSS, starter solenoid, and the starter motor itself. Corrosion is a major culprit in older vehicles. Check all wiring connections for corrosion, looseness, and breaks.
* Starter Solenoid: While you replaced the starter motor, the *solenoid* is a separate component on the starter. It's the electromagnetic switch that engages the starter motor. A bad solenoid won't allow the starter to crank.
* Security System (if equipped): If your DeVille has a factory or aftermarket security system, it might be preventing the car from starting. Check for any alarm indicators or unusual behaviors.
* Bad Ground: A poor ground connection somewhere in the system can prevent proper electrical flow to the starter. Check the battery ground cable and the engine block ground for good contact and clean surfaces.
* Incorrect Installation: It's possible one of the new parts was installed incorrectly, leading to an open circuit or short. Double-check all connections.
* Crankshaft Position Sensor (CKP): This sensor tells the engine's computer where the crankshaft is. If it's faulty, the computer might not send the signal to allow the starter to engage. (Less likely, but possible).
Troubleshooting Steps:
1. Check for Power at the Starter: With the key in the "start" position, test for power at the large cable going to the starter. If no power, the problem is upstream (ignition switch, NSS, wiring). If there is power, the problem is likely the starter motor or solenoid itself.
2. Test the Neutral Safety Switch: Check the continuity of the NSS with a multimeter. This ensures it's closing the circuit when the transmission is in Park or Neutral.
3. Inspect All Wiring: Carefully examine all wiring related to the starting system for breaks, corrosion, and loose connections.
4. Check Grounds: Clean all ground connections, especially the battery ground cable and the engine ground.
If you're not comfortable working on automotive electrical systems, it's best to take your DeVille to a qualified mechanic for diagnosis and repair. Trying to troubleshoot electrical problems without the right knowledge and tools can lead to further damage.
