1. Fuel Pump & Pressure:
* Fuel Pressure Test: This is the *most crucial* step. You need a fuel pressure gauge to measure the fuel pressure at the fuel rail when cranking the engine *cold*. The specification for your 4.3L engine should be readily available online (check a GM repair manual or a reputable auto parts website). Low pressure or no pressure when cranking points directly to a fuel delivery problem. Even if the pump runs, it might not be producing enough pressure when cold.
* Fuel Pump Operation: Listen carefully near the fuel tank while someone cranks the engine. You should hear the pump whirring for a few seconds before cranking. If you don't hear it, check the pump's power supply at the pump itself. A weak pump can deliver adequate pressure when warm but fail when cold due to increased viscosity of the fuel.
* Fuel Filter: A clogged fuel filter restricts fuel flow, especially when cold. This is a cheap and easy part to replace.
2. Crankshaft Position Sensor (CKP Sensor):
* The CKP sensor tells the engine's computer the position of the crankshaft. A faulty sensor can prevent the engine from starting, especially when cold. While less likely than a fuel issue, it's worth considering, especially if the engine cranks normally but doesn't fire.
3. Mass Airflow Sensor (MAF Sensor):
* A dirty or faulty MAF sensor can cause starting problems, particularly when cold. It measures the amount of air entering the engine, and incorrect readings can lead to an improper fuel/air mixture. Try cleaning the MAF sensor with MAF sensor cleaner (follow the instructions carefully).
4. Temperature Sensors:
* Several temperature sensors influence the fuel system. A faulty coolant temperature sensor or intake air temperature sensor could cause the computer to deliver an incorrect fuel mixture when cold. These are relatively inexpensive sensors to replace.
5. Other Potential Issues (Less Likely):
* Fuel Injectors: While less common, clogged or faulty fuel injectors could contribute. Injectors often show problems when cold due to fuel gelling.
* Ignition System: Although starter fluid bypasses this, a weak ignition coil or spark plugs could exacerbate the issue.
* Wiring: Check for any cracked or damaged wires in the fuel system or ignition system.
Troubleshooting Steps Summary:
1. Fuel Pressure Test (MOST IMPORTANT): This will pinpoint if the problem is fuel delivery.
2. Fuel Filter Replacement: A cheap and easy fix that often resolves fuel delivery issues.
3. Check Fuel Pump Operation (Sound & Power): Listen for the pump while cranking and test its power supply.
4. Inspect CKP and MAF sensors: Clean the MAF sensor and consider replacing it if necessary.
5. Investigate temperature sensors: Consider replacing suspect temperature sensors.
Important Note: Don't keep using starter fluid as a workaround. It's dangerous and can damage the engine. Diagnose the problem properly to avoid further issues. A fuel pressure test is the most direct way to determine if the fuel system is the cause.
