Here's a step-by-step approach:
1. Check the Obvious:
* Fuel Level: The most basic check. Is the fuel tank actually low on gas?
* Fuel Pump: Listen for the fuel pump whine when you turn the ignition key to the "ON" position (don't crank). You should hear a brief hum. If you don't, the pump may be faulty or have a power issue.
* Fuel Pump Relay: Locate the fuel pump relay (consult your owner's manual or a wiring diagram). Try swapping it with a known good relay of the same type (often interchangeable with other relays). This helps rule out a relay problem.
2. Inspect the Fuel System:
* Fuel Filter: A clogged fuel filter will restrict fuel flow. Inspect and replace it if necessary. This is a relatively inexpensive and common cause.
* Fuel Lines: Visually inspect the fuel lines from the tank to the fuel rail for cracks, leaks, or kinks. Pay close attention to connections. A loose or damaged line will prevent fuel from reaching the throttle body.
* Fuel Pressure: This is the most critical step. You'll need a fuel pressure gauge. Connect it to the fuel rail (according to gauge instructions) and check the pressure with the ignition ON (but don't crank). Compare the reading to the specifications in your owner's manual or a repair manual. Low pressure indicates a problem with the fuel pump, filter, regulator, or lines.
3. Examine Components Near the Throttle Body:
* Fuel Rail: Check for leaks at the fuel rail itself. Look for cracks or loose fittings.
* Fuel Injectors: While you may not see fuel spraying directly at the throttle body, you should be able to check for fuel pressure at the rail. If pressure is good at the rail but not at the injectors, then the problem lies within the injectors themselves or their wiring. Testing injectors requires specialized tools and knowledge, however.
* Throttle Body: Inspect the throttle body for any obstructions that might prevent fuel from entering. This is less likely, but still possible.
4. Electrical System (if fuel pump and pressure are okay):
* Fuel Injectors Wiring: Check the wiring harness leading to the fuel injectors for damage, corrosion, or loose connections.
* Computer/PCM: A faulty computer can also affect fuel delivery. This is a more advanced troubleshooting step and often requires professional diagnosis with a scan tool.
* Cranking Sensor: A faulty Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP) can prevent the computer from signaling the fuel injectors to open.
Important Notes:
* Repair Manuals: A Haynes or Chilton repair manual for your specific year and model Caprice will be invaluable. They provide diagrams, specifications, and troubleshooting guidance.
* Safety First: Fuel is flammable. Work in a well-ventilated area, away from open flames or sparks.
* Professional Help: If you're not comfortable working on your fuel system, it's best to take your vehicle to a qualified mechanic. Improper fuel system repair can be dangerous.
By following this systematic approach, you should be able to pinpoint the cause of the lack of fuel at the throttle body. Remember to address safety concerns and seek professional help if needed.
