The combination of an overworked pump, reduced cooling and lubrication will likely damage the fuel pump. A low fuel level also means less fuel to dissipate heat and lubricate the pump. This is because the reduced fuel weight no longer pushes fuel into the pump. When the fuel level is low, the pump has to work much harder to produce the same pressure. Running such a vehicle out of fuel once can permanently damage the fuel pump. This is particularly critical on late model vehicles without a fuel pressure return system. A leading cause of fuel pump failure is running the fuel tank low. Insufficient flow limits cooling and lubrication of the pump. To cool and lubricate the internal components, fuel must flow continuously through the fuel pump. Fuel flowing through the fuel pump cools and lubricates the internal components Pumps with relief valves simply dump excess pressure back to the fuel tank.

More modern systems regulate pressure by varying pump voltage or with an internal pressure relief valve. This offered an advantage of allowing fuel to cool. The fuel pressure regulator returned excess pressure from the engine fuel rail to the fuel tank. Older systems used a fuel pressure regulator in the front of the vehicle. Fuel enters the pump through the strainer, flows through the motor and exits under pressure.įuel pressure is critical and the pump maintains it within a narrow range. A small permanent magnet motor drives an integral pump. The pump is the heart of the fuel pump module and does the work of moving fuel from the tank to the injection system. A few have fuel senders and fuel filters that are separately replaceable. These fuel pump modules are most often available only as an assembly. They may also include a fuel filter, as part of the module. A sender unit sends a signal to the fuel level gauge to show the fuel level in the tank. The fuel pump module consists of a fuel pump, internal wiring, anti drain-back valve and a strainer. More modern designs employ a fuel pump module. Most vehicles today employ an electric fuel pump moduleĮarly fuel pumps were replaceable, separately from the level sensor and pickup tube. This saves installation of a fuel tank and a pump. Fuel tanks arrive at the manufacturer, complete with the pump. Placing the fuel pump in the tank also cuts assembly costs. Submerging this type pump under fuel, provides head pressure for the pump. What the rotary pump lacks in suction it more than makes up for in pressure. The design also lacks suction to draw fuel from a long distance. This style of a pump produces high pressure that is very precise. They meet these needs with a rotary displacement pump. Injected vehicles require a much higher and precisely regulated fuel pressure. When we operate the pump, we draw fuel from the tank and pump gasoline into the carburetor bowl. The diaphragm pump has good suction, but not too much pressure. These are often diaphragm pumps, mounted on the engine. The pump on these models produces between two and six pounds per square inch of pressure. Why are pumps mounted in the tank?Ĭarbureted vehicles do not need much fuel pressure. Fortunately, fuel pump failure is often preventable. This often makes replacement very expensive. These pumps are complex and can be difficult to access. Because of precise pressure requirements, modern vehicles normally use electric fuel pumps, located inside the fuel tank.

Bad fuel pump module