* Fuel Pump itself: The most obvious cause is the fuel pump itself. Heat can degrade the pump's internal components (seals, motor windings) causing it to fail or become intermittent when hot. The pump might be original or nearing the end of its lifespan and heat is the final straw.
* Fuel Pump Relay: The relay, which switches power to the fuel pump, can be affected by heat. If the relay's contacts become sticky or corroded, they might fail to make a reliable connection, especially when the engine bay temperature rises significantly. The heat expands components leading to poor contact.
* Wiring/Connections: Worn or poorly insulated wiring harness to the fuel pump can short-circuit when the engine gets hot. Expansion and contraction of the wires due to temperature changes can stress connections, leading to intermittent failure. Look for any signs of melted insulation, chafing or corrosion.
* In-tank Fuel Pump Sender Unit: This unit often includes the level sensor and the pump itself. The sensor could be causing a problem within this unit, specifically related to the heat.
* PCM (Powertrain Control Module) / Computer Issues: Though less likely, a faulty PCM can contribute. While unlikely to directly cause the pump to stop, a faulty sensor reading (like engine temperature) could cause the PCM to shut down the fuel pump as a safety measure, although this is more likely to trigger a check engine light.
Troubleshooting Steps:
1. Check the Fuel Pump Relay: Locate the relay (usually in a fuse box under the hood or dash), and try swapping it with a known good relay of the same type. If the problem goes away, replace the relay.
2. Inspect Wiring: Carefully examine all wiring leading to the fuel pump, looking for any signs of damage, corrosion, or poor connections. Pay close attention to connections at the fuel pump itself.
3. Check Fuel Pump Voltage: With the ignition on, measure the voltage at the fuel pump connector. It should be close to battery voltage (12V). If it's significantly lower or absent when the engine is hot, the problem lies in the wiring or relay.
4. Listen for the Fuel Pump: When you turn the ignition key to the "on" position (without starting the engine), you should hear the fuel pump prime for a few seconds. If you don't hear it, and you've confirmed the relay is good, it strongly suggests a fuel pump problem.
5. Consider the Fuel Pump Sender Unit: If other checks fail, this often-overlooked component requires a tank drop to inspect and test.
If you're not comfortable performing these checks yourself, taking the vehicle to a qualified mechanic is the safest course of action. They have the tools and experience to diagnose and repair the problem effectively. Remember safety first when working with fuel systems.
