Most Likely Culprits:
* Fuel Pump Relay: This is the most common and easiest to check first. Heat can cause the relay contacts to become unreliable, failing to power the fuel pump when the engine is hot. You can try swapping the fuel pump relay with another similar relay (like the horn relay, for example – *be sure to check the amperage rating first*). If the car starts and runs after swapping, the original relay is bad.
* Fuel Pump itself: The fuel pump's internal components can weaken with age and heat. The pump may be able to push fuel when cold, but lose the ability to build pressure when it gets hot. This is more involved to diagnose. You'll need a fuel pressure gauge to monitor pressure while the engine warms.
* Fuel Pump Driver Module (PCM controlled): Some systems use a module controlled by the Powertrain Control Module (PCM) to manage the fuel pump. A failing module might cut power to the pump when it gets hot. Diagnosing this usually requires a scan tool and advanced electrical knowledge.
* Clogged Fuel Filter: A severely clogged filter restricts fuel flow, and the extra strain might cause the pump to fail when it’s under load (i.e., at operating temperature).
Troubleshooting Steps:
1. Check the Fuel Pump Relay: As mentioned above, this is the easiest and quickest check. Swap it with a known good relay.
2. Check Fuel Pressure: This is crucial. You'll need a fuel pressure gauge that can connect to the Schrader valve (typically found on the fuel rail). Monitor the pressure at cold start, then let the engine run until it reaches operating temperature. Observe the pressure drop. A significant drop to zero strongly indicates a fuel pump or fuel pump relay problem. Refer to your Buick Regal's repair manual for the correct fuel pressure specifications.
3. Inspect the Fuel Filter: While not the primary suspect, a severely restricted fuel filter can contribute to the problem. A visual inspection can sometimes reveal a heavily clogged filter.
4. Check Wiring: Look for any obvious damage or corrosion in the wiring harness leading to the fuel pump and relay. Heat can exacerbate problems with frayed or poorly connected wires.
5. Advanced Diagnostics: If the above steps don't identify the problem, you might need a scan tool capable of reading PCM data to check for fuel system codes. This will often require professional-level diagnostics.
Important Safety Note: Always disconnect the negative battery terminal before working on any fuel system components. Gasoline is highly flammable.
If you're not comfortable working on your car's fuel system, it's best to take it to a qualified mechanic. Misdiagnosis and improper repair can be dangerous.
