1. Verify Fuel Delivery:
* Fuel Pressure: Even with a new fuel pump, you need to verify it's delivering the correct fuel pressure. You'll need a fuel pressure gauge to test this at the fuel rail. The correct pressure should be specified in your owner's manual or a repair manual for your specific engine. Low pressure indicates a problem beyond the pump (e.g., clogged fuel filter, pressure regulator).
* Fuel at the Injectors: After confirming pressure, you can check if fuel is actually reaching the injectors. You can do this by removing a fuel injector and cranking the engine (with the injector disconnected, obviously, to avoid spraying fuel everywhere). You should see fuel spraying out. If not, there's a blockage somewhere between the pump and injectors, or there is an issue with the fuel injectors themselves.
2. Ignition System:
* Spark: The next crucial check is spark. You need a spark tester or a good spark plug wire tester to check if spark is reaching the spark plugs. No spark points to problems with the ignition coil, ignition control module (ICM), distributor cap and rotor (if equipped), crankshaft position sensor (CKP), or wiring.
* Spark Plug Wires: While checking for spark, also inspect the spark plug wires for cracks or damage. Worn wires can cause a weak or intermittent spark.
* Ignition Coil: A failing ignition coil is a common cause of no-start issues.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position, which is crucial for timing the spark. A faulty CKP will prevent starting.
3. Other Possibilities:
* Camshaft Position Sensor (CMP): Similar to the CKP, a faulty CMP can prevent the engine from starting.
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor can cause the engine to run poorly or not start at all. Try disconnecting the MAF sensor and see if the truck starts. This is a temporary measure, and the sensor might need cleaning or replacement.
* Battery and Connections: Ensure your battery is fully charged and the terminals are clean and tight. A weak battery can sometimes prevent starting, especially if the starter is drawing extra current due to a faulty component.
* Security System: If your Tahoe has a factory or aftermarket security system, it could be preventing the engine from starting. Check for any warning lights or unusual behavior related to the security system.
* PCM (Powertrain Control Module): In rare cases, a faulty PCM can cause no-start conditions. This is usually diagnosed by a professional mechanic with specialized equipment.
Troubleshooting Steps:
1. Check fuel pressure: This is the most important step after replacing the fuel pump.
2. Check for spark: This is the second most crucial check.
3. Inspect related components: Check ignition coil, wires, sensors (CKP, CMP, MAF), and battery.
4. Consult a repair manual: A repair manual specific to your 1997 Chevy Tahoe will provide detailed diagrams, specifications, and troubleshooting procedures.
If you're not comfortable working on your vehicle's electrical system, it's best to take it to a qualified mechanic for diagnosis and repair. Trying to troubleshoot these issues without the proper knowledge and tools can be dangerous and lead to further damage.
