Here's why it's so complex and what's involved:
* No Direct Replacement: There's no readily available carburetor intake manifold designed to directly replace the TBI system on a 1989 1500. You'll need to find a suitable manifold from a different vehicle (possibly an older model truck with a carburetor) or have one custom-fabricated. This itself is a significant project requiring specialized tools and knowledge.
* Fuel System Overhaul: The entire fuel system needs to be changed. You'll need to:
* Remove the fuel pump and lines: The high-pressure fuel pump used for fuel injection is incompatible with a carburetor. You'll need a low-pressure fuel pump designed for carburetor systems.
* Install new fuel lines: Fuel injection uses different lines and fittings than a carburetor.
* Add a fuel filter: Carburetor systems typically require a fuel filter.
* Potentially add a fuel pressure regulator: Depending on the chosen carburetor and fuel pump, a regulator might be necessary.
* Ignition System Adjustments: While the ignition system might not need complete replacement, it likely will need adjustments to properly time and control the spark with a carburetor.
* ECM Removal: The Electronic Control Module (ECM) that controls the fuel injection system must be removed. This changes how the engine is controlled and you might need to re-wire some aspects of the electrical system.
* Wiring Changes: The wiring harness will require significant modifications to eliminate the fuel injection components and any related sensors.
* Vacuum Lines: The vacuum system will need to be rerouted to work with the carburetor, supplying vacuum to the brake booster, distributor advance (if applicable), and other components.
* Emissions System: The vehicle's emissions system is likely designed for fuel injection. Converting to a carburetor will almost certainly make it fail emissions testing. This is a serious concern and could lead to legal issues depending on your local regulations.
* Calibration and Tuning: Once everything is installed, the carburetor needs to be carefully calibrated and tuned for your engine. This requires considerable expertise and specialized tools. Improper tuning can lead to poor performance, poor fuel economy, and engine damage.
In short: Converting your 1989 Chevy 1500 from fuel injection to a carburetor is a massive undertaking best left to experienced engine builders and mechanics with access to specialized tools and equipment. The cost and effort involved likely outweigh any perceived benefits. It's far more practical and cost-effective to repair or replace the fuel injection system if you're having problems.
