1. Verify the basics:
* Fuel Pump Pressure: You say you have fuel *at* the throttle body, but that doesn't guarantee sufficient pressure. You *must* check fuel pressure at the fuel rail with a fuel pressure gauge. Your car should have a specific pressure rating (consult your repair manual), typically in the 12-14 psi range for a TBI system. Low pressure points to a failing fuel pump, clogged fuel filter, or other fuel delivery issue. This is the most likely culprit given your description.
* Battery Voltage: While you mention voltage *at* the throttle body, ensure your battery has sufficient voltage (12.6V or higher when not cranking). A weak battery can prevent the fuel injection system from operating correctly. Test both at the battery terminals and at the throttle body connector.
* Ignition System: Although you're focusing on fuel, a weak spark can prevent a proper combustion event even with fuel. Check for spark at the spark plugs. A simple way is to remove a plug wire, ground the end of the wire (using pliers, ensuring it's well-grounded to the engine block), and crank the engine. A strong blue spark should be visible. Weak or no spark suggests problems with the ignition coil, distributor (if equipped), ignition module, or related wiring.
2. Investigate the TBI System:
* Throttle Position Sensor (TPS): A faulty TPS can prevent the computer from signaling the injectors to fire. Check the TPS voltage using a multimeter while moving the throttle plate. The voltage should change smoothly from near 0V to 5V (or similar, check your specifications). A stuck or erratic TPS will stop fuel delivery.
* Computer (ECM): The ECM controls the injectors. A faulty ECM is less likely, but possible. This is much harder to test without specialized tools or an advanced understanding of diagnostics.
* Injector Pulse: The easiest way to test if the injectors are receiving the signal to open is to use a "noid light" or a test light connected to the injector connector wire. When cranking, the noid light should flash, indicating a pulse signal. Lack of flashing means the injector is not receiving the signal from the ECM.
* Cranking Sensor: The Crankshaft Position Sensor (CKP) or Crankshaft sensor (CMP) tells the ECM the engine is cranking, triggering fuel injection. A bad CKP sensor can prevent fuel delivery.
3. Check for Codes:
Your 1992 Camaro likely has a diagnostic port (ALDL) under the dash. A scan tool or jumper wire can be used to retrieve diagnostic trouble codes (DTCs) stored by the ECM. These codes can pinpoint the problem.
4. Fuel Injector Relay: This relay supplies power to the injectors. Make sure it's clicking when the ignition is on. A bad relay could be the simple culprit.
Important Notes:
* Repair Manual: A factory service manual for your specific year and model is invaluable. It provides wiring diagrams, specifications, and troubleshooting procedures.
* Safety: Disconnect the negative battery terminal before performing any electrical tests to avoid short circuits.
* Professional Help: If you're not comfortable working on your car's electrical system, take it to a qualified mechanic.
By systematically checking these points, you should be able to isolate the cause of the no-start condition. The fuel pressure test is the most critical first step. If you find low fuel pressure, you can then start troubleshooting the fuel pump, filter, and fuel lines.
