However, the behavior you describe—pressure building with the key then dropping to zero—strongly suggests a problem. Here's what's likely happening and what to check:
* Fuel Pump Failure: This is the most common cause. The pump builds pressure initially, but it can't maintain it due to a failing pump, a worn-out pump motor, or a blockage in the fuel system.
* Check Valve Failure: The check valve in the fuel system is supposed to hold pressure when the pump is off. If it's faulty, the pressure will bleed off.
* Leak in the Fuel System: A leak anywhere in the fuel lines, injectors, or fuel pressure regulator will cause the pressure to drop.
* Fuel Pressure Regulator Problem: A faulty fuel pressure regulator may be allowing fuel to leak back into the tank.
* Wiring Issue: A problem in the wiring to the fuel pump relay or the pump itself could prevent the pump from running consistently.
Troubleshooting Steps:
1. Consult your owner's manual: Find the correct fuel pressure specification for your specific engine and fuel system.
2. Use a Fuel Pressure Gauge: Connect a fuel pressure gauge to the fuel system's test port (location varies depending on the year and engine). This will give you an accurate reading of the pressure. You'll need an adapter to connect the gauge.
3. Listen for the fuel pump: With the key on, you should hear the fuel pump run for a few seconds (if the pump is functioning). If you don't hear it, the pump, relay, or wiring might be the problem.
4. Check fuel lines and connections: Inspect the fuel lines for cracks, leaks, or loose connections.
Do not attempt any fuel system repairs yourself unless you have experience working with fuel systems and are familiar with safety precautions for handling gasoline. Fuel is extremely flammable, and mistakes can lead to serious injury or fire. If you are unsure about any part of this process, take your Suburban to a qualified mechanic.
