* Crank Position Sensor (CKP): This sensor tells the computer the engine's rotational position, crucial for precise ignition timing. A faulty CKP prevents the computer from sending the signal to fire the coils. This is a very common culprit in no-start situations.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft. A bad CMP also prevents proper ignition timing.
* Ignition Control Module (ICM): This module controls the firing of the coils. While you've replaced the coils, the ICM itself could be faulty.
* Distributor (if applicable): Some Lumina vans might have distributors. Check for any wear, damage, or issues within the distributor cap, rotor, or the distributor itself. (Less likely given you mention new coils, but worth considering if present).
* Computer (PCM/ECM): Though less likely, a faulty Powertrain Control Module (PCM) or Engine Control Module (ECM) could be preventing the ignition system from functioning correctly.
* Wiring: Check all the wiring related to the ignition system – from the sensors to the coils, the ICM, and the computer. Look for any broken, frayed, or corroded wires. A simple short could prevent firing.
* Fuel System: While you say it's a firing issue, make absolutely sure you have fuel pressure. A no-start can sometimes be masked as an ignition problem when it's actually a fuel delivery issue.
Troubleshooting Steps:
1. Check for Spark: With a spark tester or even a spare spark plug wired to a ground, test for spark at each coil's output. If there's no spark at all, the problem is upstream of the coils (CKP, CMP, ICM, PCM, or wiring). If you have spark at some but not all, check for problems with the wiring to the specific coils not firing.
2. Check CKP and CMP Sensors: Use a multimeter to check the sensor readings against the factory specifications in your vehicle's repair manual. These often read voltage changes as the engine is cranked.
3. Inspect the ICM: Visually inspect the ICM for any signs of damage. Testing requires a multimeter and knowledge of the module's specifications.
4. Check Fuel Pressure (crucial): Use a fuel pressure gauge to check the fuel pressure at the fuel rail. Low or no pressure means a fuel pump, fuel filter, or fuel regulator issue.
5. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any trouble codes stored in the PCM. This can point you directly to the faulty component.
It's best to start with the simpler checks (spark, fuel pressure, DTCs) before moving onto more complex components like the sensors and the computer. A repair manual specific to your 1996 Chevy Lumina van will be invaluable for detailed troubleshooting steps, wiring diagrams, and component specifications.
