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Fuel Pump Diagnosis Tips from Carter (PDF file – requires Adobe Acrobat Reader to view).
So, There are basically two types:
How Do Electric Fuel Pumps Work
So, when the driver turns the ignition key on; the (PCM) energizes a relay that supplies voltage to the pump. As a result, the motor inside the pump starts to spin. Then, runs for a few seconds to build pressure. Consequently, a timer in the (PCM) limits how long the pump will run until the engine starts. Next, fuel is drawn into the pump; through an inlet tube and mesh filter sock. Finally, the fuel then exits the pump, through a one-way check valve.
So, a fuel filter traps any rust; dirt or other solid contaminants; that may have passed through the pump. As a result, preventing such particles from clogging the injectors.
So, the fuel then flows to the supply rail on the engine. And, is routed to the individual injectors. Consequently, a pressure regulator on the rail maintains pressure; and routes excess fuel back to the tank. But, on newer vehicles with return less (EFI) systems; the pressure regulator is located in the tank. Consequently, it is part of the pump module. As a result, there is no return line, from the engine back to the tank.
Fuel pumps are not part of a regular maintenance schedule and only need to be replaced when they fail. Most pumps should last well past 100,000 miles.
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