Technical
Fuel Pump 101 The basics of fuel pump diagnosis and repair Electric fuel pumps are among the most reliable parts of a car. Under normal conditions, it’s not uncommon for a pump to last the whole life of the vehicle. When it finally quits, it’s because the motor is worn out and can’t develop enough torque to generate the correct fuel pressure. Here are the basics for what it takes to diagnose a problem and perform a profitable repair.
By Jacques Gordon
system filter, and of course the electric fuel pump. An electric fuel pump consists of two he most common cause of fuel pump parts: a small brush-type DC motor and the failure is frequently running the tank pump itself. This assembly is submerged in a low on fuel, which causes the motor to reservoir of fuel that keeps the motor cool and overheat. The second most common cause is prevents air from getting to the motor, thus fuel contamination, usually dirt and rust par- eliminating the risk of fire or explosion. ticles that clog the fuel strainer and prevent Pump and gauge the pump from drawing enough fuel under Fuel outlet electrical connections high engine load. If enough contamination Tank vent and EVAP gets past the pump’s intake strainer, it can connections actually jam the pump and stop the engine immediately. Diagnosing fuel pressure problems is often Fuel tank tricky because the problem can be something pressure other than the fuel pump. To help you avoid sensor misdiagnosis and comebacks, we’re going to review the components of a fuel pump assembly, describe some diagnostic techniques, and discuss how to give replacement fuel pumps a good chance at a long service life. We’ll focus only on port fuel injection systems that use Motor/pump assembly the electric pump to generate all the pressure with integral Fuel pump in the system, but most of this information pressure reservoir regulator can also apply to the fuel delivery system of direct-injection engines, too.
Fuel pump The complete fuel pump assembly might include a fuel gauge sending unit, a pressure regulator valve, a fuel tank pressure sensor, a pump intake strainer and/or the main fuel 12 | ASP October 2017
Fuel gauge float
Photo courtesy of Carter Fuel Systems
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