In general, a faulty Fuel Pump is not directly the cause of fuel spillage when refueling. However, the Fuel Pump does contribute indirectly whenever its malfunctioning affects the overall fuel delivery and pressure system. The most probable cause of spilling fuel during refueling lies within the vehicle’s fuel system, especially within the EVAP or its fuel tank venting system.
The EVAP system is a design meant to manage fuel vapors and not allow them to reach the atmosphere. The Fuel Pump works inefficiently, leading to imbalance pressure inside the fuel tank that might also affect the overloading on the system’s ability for proper venting. Due to this, the increased pressure while refueling can’t be handled by the tank, which in turn causes fuel spilling.
A study by Automotive News estimated that more than 40% of fuel spills at the pump are caused by issues related to the fuel tank and its associated components, such as a clogged vent hose or malfunctioning valve, which sometimes can be related to problems with the Fuel Pump. When these components are not working correctly, they cannot relieve pressure during refueling, and fuel may spill from the tank.
In some instances, a malfunctioning Fuel Pump might send more fuel than required into the tank, raising the internal pressure beyond the point at which it will spill. This is more likely to happen with an older car or one that has seen extensive wear and tear on the fuel delivery system. For instance, a 2017 survey conducted by Consumer Reports found that those vehicles with older fuel pumps were three times more likely to develop problems with fuel delivery that could promote improper fuel venting and subsequent spillage during refueling.
“Fuel spills are a clear indication that the fuel system isn’t working properly,” says Jeff Anderson, a mechanic at Precision Auto Repair. “A faulty Fuel Pump may not seem like the obvious culprit, but it can definitely exacerbate the situation if it’s creating pressure imbalances in the fuel tank.”
Fuel spillage during refueling can also be caused by a blocked or defective filler neck, the component that connects the fuel nozzle to the tank. A malfunctioning Fuel Pump can result in excessive fuel pressure, which may be more than this neck can handle, hence the spillage. This usually happens more in fuel-injected vehicles or those with high-performance engines where the fuel pressure is abnormally high.
The fuel filter of the Fuel Pump system could be clogged and hence might cause interference in the flow of fuel. Due to this clogged fuel filter, the Fuel Pump might overcompensate and result in an excessive amount of fuel flow inside the tank while refueling, which could spill out.
Sometimes, this could result in fuel spillage if the Fuel Pump is too weak to support the correct fuel pressure. The pump will be unable to push fuel into the system effectively enough, leading to irregular flow and fluctuating pressure that can cause an overflow during refueling.
For instance, one study published by AAA indicated that more than 25% of fuel system failures could be blamed on weak Fuel Pumps; these often result in the improper filling of a fuel tank or even fuel spillage. This is commonly seen in older models when the Fuel Pump is probably wearing out and losing efficiency.
Fuel spillage at the time of refueling requires an inspection of the fuel pump, tank, and associated parts in detail. Installation of an efficient, high-quality Fuel Pump can facilitate proper fuel pressure and flow without any chance of a fuel spill, so the system may function normally.