Automotive technology is evolving at an astounding rate. It is important for the car owner and the automotive technician to have useful resources and news about the development of the integral systems that make the automobile work. This fwicki was created to provide useful news, videos, and information about fuel injection technologies.
The primary functional difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on the vacuum created by intake air rushing through it to add the fuel to the airstream.
The fuel injector is only a nozzle and a valve: the power to inject the fuel comes from further back in the fuel supply, from a pump or a pressure container.
The fuel injector acts as the fuel-dispensing nozzle. It injects liquid fuel directly into the engine's air stream. In almost all cases this requires an external pump. The pump and injector are only two of several components in a complete fuel injection system.
Periodically, fuel injectors need to be serviced or replaced. The following tips will help the technician or mechanic understand general procedures involved in replacing fuel injectors:
How To Remove And Re-Install Fuel Injectors:
The following is a general overview of how to remove and replace worn or damaged fuel injectors. This process is not recommended for the novice or intermediate mechanic or automotive technician. If you are unsure about any of the steps and techniques listed below, be sure to consult a professional auto repair technician. Due to the complexity of most fuel injection systems, it is advisable to enlist the help of a certified automotive repair technician. The example given below is a general approach and your particular make and model vehicle may require specific variations of the following procedures.
Pre-Removal Steps And Techniques:
Removal Steps And Techniques:
Installation: Before installing the new injectors, test each injector for electrical resistance across the terminals. The standard is 2 to 3 Ohms.
Post-Installation:
Fuel Injection System Benefits:
The benefits of owning a fuel injected vehicle are many. Operational benefits to the driver of a fuel-injected car include smoother and more dependable engine response during quick throttle transitions, easier and more dependable engine starting, better operation at extremely high or low ambient temperatures, reduced maintenance intervals, and increased fuel efficiency.
An engine's air/fuel ratio must be accurately controlled under all operating conditions to achieve the desired engine performance, emissions, drive ability, and fuel economy. Modern electronic fuel injection systems meter fuel very accurately
The process of determining the amount of fuel, and its delivery into the engine, are known as fuel metering. Early injection systems used mechanical methods to meter fuel (non electronic, or mechanical fuel injection). Modern systems are nearly all electronic, and use an electronic solenoid (the injector) to inject the fuel. An electronic engine control unit calculates the mass of fuel to inject.
Modern fuel injection schemes follow much the same setup. There is a mass airflow sensor or manifold absolute pressure sensor at the intake, typically mounted either in the air tube feeding from the air filter box to the throttle body, or mounted directly to the throttle body itself. The mass airflow sensor does exactly what it's namesake implies; it senses the mass of the air that flows past it, giving the computer an accurate idea of how much air is entering the engine. The next component in line is the Throttle Body. The throttle body has a throttle position sensor mounted onto it, typically on the butterfly valve of the
In contrast to an EFI system, a carburetor directs the induction air through a venturi, which generates a minute difference in air pressure. The minute air pressure differences both emulsify (premix fuel with air) the fuel, and then acts as the force to push the mixture from the carburetor nozzle into the induction air stream. As more air enters the engine, a greater pressure difference is generated, and more fuel is metered into the engine. A carburetor is a self-contained fuel metering system, and is cost competitive when compared to a complete EFI system.
An EFI system requires several peripheral components in addition to the injector(s), in order to duplicate all the functions of a carburetor. A point worth noting during times of fuel metering repair is that early EFI systems are prone to diagnostic ambiguity. A single carburetor replacement can accomplish what might require numerous repair attempts to identify which one of the several EFI system components is malfunctioning. Newer EFI systems since the advent of OBD II diagnostic
Multi-Point Fuel Injection:
Multi-point fuel injection injects fuel into the intake port just upstream of the cylinder's intake valve, rather than at a central point within an intake manifold, referred to as SPFI, or single point fuel injection. MPFI systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke, batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke, or simultaneous, in which fuel is injected at the same time to all the cylinders. All modern EFI systems utilize sequential MPFI. Some Toyotas and other Japanese cars from the 1970s to the early 1990s used an application of the Bosch multipoint L-Jetronic system manufactured under license by DENSO.
