Fuel injection consists of a throttle body to control airflow, the fuel injectors, various engine sensors, an electric fuel pump and a fuel filter. The system is controlled by the vehicles powertrain control module (PCM), which makes all decisions for controlling the injection system. Most early fuel injection systems used a throttle-body design, where one or more injectors were mounted on a throttle body, resembling a carburetor. Use of the throttle body system faded away gradually as multi-port fuel injection became more prevalent. Multi-port uses a separate fuel injector for each cylinder, located near each cylinder’s intake valve port. Virtually all engines now use multi-port injection.
Fuel injection delivers fuel to the engine in exactly the right amount for all engine-operating conditions. Not only does the system provide better control for fuel economy, performance and emissions, it also does away with many of the maintenance requirements of a carburetor.
On vehicles with fuel injection, some manufacturers don't recommend replacing the filter at all during the first 100,000 miles of "normal" driving. Since “normal” usually constitutes severe driving because of less than normal conditions, it's best to replace the filter every two years or 24,000 miles. A contaminated filter can restrict fuel flow from your vehicle’s electric fuel pump, eventually taking a toll on its life. Frequent filter replacements remove all doubt about whether the filter may cause other problems down the road. On 1996 and newer vehicles, your vehicle’s fuel injection system is integrated with a second-generation onboard diagnostic system, known as OBDII. The PCM stores a Diagnostic Trouble Code (DTC) when it detects a problem in one of the monitored circuits. A professional technician at D and R Car Care and Lube Center can access this information using a scan tool connected to the vehicle’s Data Link Connector (DLC). Although many DTCs are sensor-related, it does not necessarily indicate a faulty sensor. There may be problems in that sensor’s circuit, or there may be several interrelated problems. Areas of the country with an emissions testing program are placing added value on OBDII checks, where this technology may be used in place of tailpipe testing. The system also alerts you with a Malfunction Indicator Lamp (MIL), indicating that the system has detected a problem, which could cause excessive emissions. This light is usually labeled SERVICE ENGINE SOON or CHECK ENGINE. If the light appears, you should have its cause investigated at D and R Car Care and Lube Center by a professional technician at your earliest opportunity. If the light flashes, the condition is more severe and must be checked out immediately to prevent damage to the catalytic converter.
The typical fuel filter for most fuel-injected vehicles consists of a high-pressure canister filled with filtering media. Filters may have clamped, threaded or special fittings to ensure reliable connection to the fuel system. Filters for carbureted engines may be located at the inlet of the carburetor or inline. Filters for carbureted engines do not need to withstand the same pressures as those for fuel-injected engines.
Fuel filters trap harmful contaminants that may cause problems with carburetors and intricate fuel injectors. Fuel filters for carbureted engines only clean the fuel before it enters the float bowl. Injection filters, on the other hand, clean the fuel whenever the fuel pump runs (unless the fuel injection system is a “returnless” design). Fuel moves continuously up the supply side, through the filter to the fuel rail or throttle body. The fuel that doesn't make it into the engine returns to the tank and the whole process starts over again. With a full tank of gas, the filter may clean the volume of fuel in the tank many times before it's all used.
On carbureted cars, replace the filter once a year. On cars with fuel injection, some manufactures don't recommend replacing the filter at all during the first 100,000 miles of "normal" driving. Since “normal” usually constitutes severe driving because of less than normal conditions, it's best to replace the filter every two years or 24,000 miles. A contaminated filter can restrict fuel flow from your vehicle’s electric fuel pump, eventually taking a toll on its life. Frequent filter replacements remove all doubt about whether the filter may cause other problems down the road. Most filters on domestic cars and trucks hide underneath on the frame or body. Just the opposite is true on the imports. They usually put their filters somewhere in the engine compartment. If you decide to change the filter yourself, be careful. Fuel injection systems maintain pressure in the lines that must be relieved prior to filter replacement. Don’t forget that gasoline is extremely flammable. Procedures vary for relieving pressure. Also, some filters require special tools to replace the fuel filter. Because of these technicalities and because of most filter locations, it’s best to have your vehicle’s fuel filter replaced by a qualified service professional at D and R Car Care and Lube Center.
A mechanical fuel pump is most often used on vehicles with carburetors. This type of pump produces low pressure and is usually driven by the engine. Vehicles all use electric fuel pumps nowadays because of the universal application of fuel injection and its need for higher pressures. Electric fuel pumps are almost always located inside the gas tank, but there are some applications where the pump may be located along the frame or unibody channel. The pump has a strainer at its pickup to filter out contaminants and uses an electric motor for power. Fuel is used as a lubricant and coolant for the motor. The electric fuel pump has its own electrical control circuit, typically consisting of wiring, a fuse and a relay. This circuit interacts with the vehicle’s powertrain control module (PCM), which governs and monitors fuel pump operation.
The fuel pump provides fuel with the proper pressure and volume for delivery by the carburetor or fuel injection system. The electric fuel pump circuit also employs various safeties that stop the pump from running in the event of an accident.
Mechanical fuel pumps require no maintenance, but should be replaced at the first sign of a problem. Pressure or volume may drop off, giving an early warning sign of impending pump failure. A professional service technician at D and R Care Car and Lube Center can usually identify a pump problem quickly. With fuel-injected vehicles, regular fuel filter changes can help extend the life of the electric fuel pump. It's best to replace the filter every two years or 24,000 miles. A contaminated filter can restrict fuel flow from the electric fuel pump, eventually taking a toll on its life. You can also help protect the pump by keeping the tank at least a 1/4 full at all times. Since fuel cools the pump, having plenty of fuel in the tank helps keep the pump from getting too warm, which could damage it. Another good reason to keep the gas tank at least a 1/4 full is to reduce the chances of sediment pick-up at the fuel pump inlet strainer. A restricted strainer can starve the pump, causing it to overheat and fail. If you own a Ford or Lincoln-Mercury vehicle, check your owner’s manual for the location of the fuel pump shut-off switch. This switch is designed to electrically disconnect the fuel pump in the event of an accident. Sometimes, an abrupt jarring of your car may be enough to cause this switch to open. It’s good to know where the switch is so you can try resetting it if your car does not start. A faulty electric fuel pump can cause various symptoms including a loud pump whine, engine no-start, hesitation, poor performance and stalling. If your vehicle demonstrates any of these performance problems, have it checked out by a qualified service technician at D and R Car Care and Lube Center . Replacing the fuel pump generally involves removal of the fuel tank.