* Clogged Injectors: This is the most common culprit. Fuel injectors can become clogged with debris or varnish over time, preventing proper fuel flow. Cleaning or replacing them is often the solution.
* Low Fuel Pressure: The fuel pump might be weak, the fuel filter clogged, or there might be a leak in the fuel lines reducing pressure below what the injectors need to operate correctly. A fuel pressure gauge is essential for diagnosing this.
* Faulty Fuel Pump Relay or Circuit: The fuel pump might not be receiving power. Check the relay and wiring for continuity and proper voltage.
* Inefficient or Failed Injector Driver Module (IDM): This module controls the electrical signal to the injectors. A faulty IDM will prevent the injectors from opening.
* Problems with the TBI Unit Itself: While fuel is reaching the TBI, there might be an internal problem within the TBI unit itself, such as a faulty pressure regulator or a problem with the passages delivering fuel to the injectors.
* Faulty PCM (Powertrain Control Module): The PCM controls many aspects of the fuel injection system. A faulty PCM can cause a wide range of issues, including injector problems. This is less likely but possible.
* Vacuum Leaks: A significant vacuum leak can affect the fuel pressure and the operation of the TBI system.
Troubleshooting Steps:
1. Check Fuel Pressure: This is the most important first step. You'll need a fuel pressure gauge to measure the pressure at the TBI fuel rail. Compare your reading to the specifications in your repair manual.
2. Inspect Fuel Filter: Replace the fuel filter if it's old or dirty.
3. Inspect Fuel Pump Relay and Wiring: Check for continuity and proper voltage.
4. Check Injector Wiring: Verify that the injectors are receiving power and ground signals. A multimeter can be used to check this.
5. Manually Test Injectors (Careful!): With the key on, you can use a test light or multimeter to verify if the injectors are getting a pulse. CAUTION: Do not crank the engine while performing this test. You may also be able to test the injectors off the vehicle using a fuel injector tester tool.
6. Inspect TBI Unit: Look for any obvious signs of damage or debris.
Recommendation: If you're not comfortable working on fuel systems, it's best to take your Suburban to a qualified mechanic. Working with fuel systems requires caution and the right tools to avoid injury or further damage. A diagnostic scan tool can also help pinpoint the problem.
