* Fuel Pump Relay: Even with a new pump, a faulty relay might not be sending power to the pump. This is a common and inexpensive part to replace. Try swapping the relay with a known good one (often another relay of the same amperage in the fuse box is a good test).
* Fuel Pump Inertia Switch: This safety device cuts power to the fuel pump after a collision. It's usually a small, button-like switch, often located under the dash or in the engine compartment. Resetting it (pushing the button) might solve the problem if it tripped inadvertently.
* Clogged Fuel Filter: A new pump doesn't guarantee a clean fuel line. A clogged fuel filter restricts fuel flow, preventing the pump from creating sufficient pressure. Replace the filter.
* Wiring Issues: Check the wiring between the fuel pump relay, the inertia switch, and the fuel pump itself. Look for corrosion, breaks, or loose connections. A bad ground is another possibility.
* Fuel Pump Wiring Harness Connector: The connector between the wiring harness and the fuel pump can become corroded or damaged, preventing the pump from getting the necessary power.
* Fuel Pressure Regulator (FPR): While less likely if the problem only occurs before starting, a faulty FPR could leak pressure back into the fuel tank, preventing sufficient pressure buildup when the engine is not running. It regulates fuel pressure, and a malfunction can cause the problem.
* Low Fuel Level: Although less likely given it runs after intake injection, a very low fuel level *could* cause problems drawing fuel for the pump (though it would generally manifest as poor high-rpm performance rather than a complete lack of pressure).
Troubleshooting Steps:
1. Check the fuel pump relay and inertia switch first. These are the easiest and cheapest things to check.
2. Check the fuel filter. It's relatively inexpensive and easy to replace.
3. Visually inspect the fuel pump wiring harness and connector for any damage.
4. Use a fuel pressure gauge to measure the actual fuel pressure at the fuel rail. This provides definitive proof of pressure or its absence. This is the most conclusive step to diagnose this.
By systematically eliminating these possibilities, you should be able to pinpoint the reason why your Suburban won't start without the added fuel in the intake. Remember safety precautions when working with fuel systems.
