Fuel Delivery System:
* Fuel Filter: A clogged fuel filter will restrict fuel flow. This is a relatively cheap and easy part to replace first.
* Fuel Injectors: Clogged or faulty injectors can prevent fuel from being sprayed into the cylinders. They might require cleaning or replacement.
* Fuel Pressure Regulator: This regulates the pressure in the fuel rail. A faulty regulator might not maintain the correct pressure, leading to insufficient fuel delivery. A pressure gauge test is needed to diagnose this.
* Fuel Rail: Though less common, a crack or leak in the fuel rail itself can cause a loss of pressure.
* Fuel Pump Relay: Even if the pump is good, a bad relay won't send power to it. A simple swap with a known good relay from another circuit (check your owner's manual for proper identification and safety precautions) can quickly diagnose this.
* Inertia Switch: This safety device cuts power to the fuel pump in a collision. It may need to be reset (usually a small button on the switch itself, often located in the passenger compartment).
Ignition System (While you say you have spark, there's an overlap):
* Computer/PCM (Powertrain Control Module): The computer controls fuel delivery. A faulty PCM can send incorrect signals to the fuel system components. This is a more complex diagnosis and may require professional help.
* Cranking System: While you have spark, a weak cranking system (battery, starter, etc.) might not spin the engine fast enough to build enough pressure to overcome fuel delivery issues. This isn't directly fuel-related, but can mask fuel problems.
* Wiring: Check all wiring related to the fuel system for shorts, breaks, corrosion, or loose connections.
Diagnostics:
Before replacing parts haphazardly, you should:
1. Check fuel pressure: Use a fuel pressure gauge to measure the pressure at the fuel rail. This is crucial to determine if the problem is with the pump or something downstream.
2. Inspect the fuel filter: A visual inspection can show if it's clogged.
3. Listen for the fuel pump: Turn the ignition key to the "on" position (don't crank). You should hear the pump briefly run. If you don't hear it, this is a good sign the pump or its relay is bad.
4. Check for fuel at the injectors: You can remove the fuel line from an injector, crank the engine, and see if fuel comes out. *Caution: Fuel is flammable and potentially dangerous to handle. Take appropriate safety precautions.*
5. Check for codes: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs) stored in the computer's memory. These codes can provide valuable clues.
Remember safety first when working with fuel and automotive systems. If you're not comfortable performing these checks or repairs yourself, take your Bronco to a qualified mechanic.
