Safety First:
* Disconnect the battery's negative terminal. This is crucial to prevent accidental short circuits.
* Wear safety glasses. Small parts might fly, and fuel could spray.
* Work in a well-ventilated area. Fuel vapors are flammable.
* Have a fire extinguisher nearby.
Tools You'll Need:
* Socket wrench set (metric and standard, depending on your truck)
* Ratchet and extensions
* Screwdrivers (Phillips and flathead)
* Fuel line disconnect tool (or pliers, but the tool is recommended)
* Vacuum line removal tools (if needed)
* Shop towels or rags
* Container to catch fuel
* Possibly a fuel pressure gauge (helpful but not strictly necessary)
Procedure:
1. Locate the TBI unit: It's mounted on the intake manifold, usually near the top of the engine.
2. Disconnect the electrical connectors: Carefully unplug all electrical connectors from the TBI unit. Take note of their positions for reassembly. Labeling them with tape and a marker is a good idea.
3. Disconnect the fuel lines: This is where the fuel line disconnect tool comes in handy. It prevents damage to the fuel lines. If you don't have one, carefully use pliers, being extremely cautious not to pinch or kink the lines. Have your container ready to catch any spilled fuel.
4. Disconnect the vacuum lines: Carefully disconnect any vacuum lines connected to the TBI unit. Again, note their positions.
5. Remove the throttle linkage: This usually involves removing a bolt or clip securing the linkage to the throttle plate.
6. Remove the TBI unit: The TBI unit is usually bolted to the intake manifold. Use your socket wrench to remove these bolts. Be careful not to drop any bolts into the intake manifold.
7. Inspect the gasket: The gasket between the TBI unit and the intake manifold should be carefully removed and inspected for damage. Replace it with a new gasket during reassembly.
Important Considerations:
* Fuel Pressure: Before disconnecting the fuel lines, consider relieving fuel pressure in the system. Consult your repair manual for the specific procedure. This is generally done by disconnecting the fuel pump relay, then starting and running the engine until it stalls.
* Intake Manifold Gasket: As mentioned, replace the gasket. A damaged gasket will lead to vacuum leaks and poor engine performance.
* Cleaning: Clean the mounting surface on the intake manifold before reinstalling the TBI unit.
Reassembly:
Reassembly is the reverse of the removal process. Ensure all connections are secure and tight. Double-check all electrical connectors and vacuum lines. Reconnect the battery's negative terminal. Start the engine and check for any leaks or unusual sounds.
Disclaimer: This is a general guide. Always consult a repair manual specific to your 1994 Chevy 3500 454 for detailed instructions and diagrams. If you're not comfortable performing this task yourself, take your vehicle to a qualified mechanic. Improperly working on your fuel system can be dangerous.
