If the engine is running rich less oxygen in the exhaust , the computer shortens the pulse width of the injectors to lean the fuel mixture. It is located on the side of the throttle body and uses a variable resistor that changes resistance as the throttle opens and closes.
It may be mounted on the intake manifold or attached to the intake manifold with a vacuum hose. The temperature of the air entering the engine must also be monitored to compensate for changes in air density that occur colder air is denser than hot air.
This tells the computer when the engine is cold and when it is at normal operating temperature. The computer needs to know the temperature because a cold engine requires a richer fuel mixture when it is first started. When the coolant reaches a certain temperature, the engine goes into Closed Loop operation, which means it starts using inputs from the oxygen sensors to fine tune the fuel mixture.
When it is operating in Open Loop when cold or when there is no signal from the coolant sensor , the fuel mixture is fixed and does not change. Faulty inputs from any of the engine's sensors may cause drivability, emissions or performance problems.
Reading the code s with a scan tool will help you diagnose the problem. Idle speed on fuel injected engines is computer controlled via an idle air bypass circuit on the throttle body. A small electric motor or solenoid is used to open and close the bypass orifice. The larger the opening, the greater the volume of air that can bypass the throttle plates and the faster the idle speed. On newer vehicles with electronic throttle control, the computer also controls the opening of the throttle plate when the driver pushes down on the gas pedal.
Position sensors in the gas pedal signal the computer how far to open the throttle plate. Idle problems on EFI systems can be caused by varnish and dirt deposits in the throttle body idle control circuit. Cleaning the throttle body with throttle body cleaner can often solve idle problems follow the directions on the product. Idle problems can also be caused by air leaks between the airflow sensor and throttle, the throttle body and intake manifold, and the intake manifold and cylinder head s , or in the PCV or EGR systems, or vacuum hoses.
A fuel injector is nothing more than a spring-loaded solenoid pintle valve. When energized by the computer, the solenoid pulls the valve open.
This allows fuel to spray out of the nozzle and into the engine. When the computer cuts the circuit that powers the injector, the valve inside the injector snaps shut and fuel delivery stops.
The total amount of fuel delivered is controlled by cycling the injector voltage on and off very rapidly. The longer the pulse width, the greater the volume of fuel delivered and the richer the fuel mixture.
Decreasing the duration of the injector signal pulse reduces the volume of fuel delivered and leans out the mixture. Dirty fuel injectors are a common problem.
A buildup of fuel varnish deposits inside the tip of the injector spray nozzle can restrict fuel delivery and interfere with the creation of a good spray pattern.
There are a number of different fuel injection systems out there, but they can all be sorted into two categories: mechanical fuel injection and electronic fuel injection. Electronic fuel injection allows for extremely precise control over how much fuel is sprayed into the cylinders. It follows a fairly straightforward process to do so:. The fuel exits the fuel tank via the fuel pump. It travels through fuel lines towards the engine. The fuel pressure regulator constricts the flow of fuel and only lets a calculated amount through to the injectors.
The fuel pressure regulator knows how much fuel to let through to the injectors via a signal from the mass airflow sensor MAF. This sensor tracks how much air is entering the engine at any given time. The fuel injectors themselves open to let the atomized gas directly into the combustion chamber or into a throttle body. The main difference between the two systems is that mechanical fuel injection systems use mechanical devices to meter the correct amount of fuel into the engine.
These systems have to be tuned for optimal performance, like carburetors, but also deliver fuel via injectors. They were, however, extremely useful for aircraft engines. Carburetors do not work well against gravity. To deal with the g-forces dealt out by aircraft, fuel injection was developed. Without fuel injection, fuel starvation would have stalled many aircraft engines during tricky maneuvers. Going forward, fuel injection will become more and more precise and offer increasing efficiency and safety.
Each year engines have more horsepower and produce less waste per horsepower. Our certified mobile mechanics perform over services, including diagnostics, brakes, oil changes, scheduled mileage maintenances, and will come to you with all necessary parts and tools. There are many questions that have come up about the way contractors must deal with lead-based paint.
For some time now, handouts and brochures have sat on the paint counters of all the local home improvement centers and paint stores. These highlight the many potential issues with lead-based paint. We sent our own Tom Gaige […]. Few people really enjoy it when the government expands regulations. We go over just what is […]. Perhaps you just want to blast through your project at lightning speeds. No more gummed up floats. No more clogged orifices. This website uses cookies so that we can provide you with the best user experience possible.
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If you disable this cookie, we will not be able to save your preferences. This means that every time you visit this website you will need to enable or disable cookies again. Direct Injection is one that can be used in low-emission lean-burn engines. Sensors are installed in numerous points of the engine and their function is to send out information to the ECU. The following sensors are used:. Actuators are components that obtain information from ECU and they act in the feeding system, varying the volume of fuel that the engine receives.
The Electronic Control Unit is responsible for the measurement of the sensors and the estimation of the action for each actuator with regard to timing restrictions. The block diagram of the Fuel Injection System is as shown in the Fig. The time constraints of the system are imposed by the characteristics of the internal combustion engine to be controlled. It is defined that a turn of the engine i.
Considering these timing constraint, the reading of the sensors and the calculation of the acting times for the actuators should be processed in at most 15 milli seconds. The Fuel Injection System consists of many sensors positioned all around your vehicle as shown in the Fig. Every time you start your vehicle, the Electronic Control Unit ECU scans each and every one of these sensors to verify their functionality.
The sensors continuously detect the values of numerous parameters like air pressure, air temperature, throttle angle, air density, fuel temperature, fuel pressure, oil pressure, coolant temperature, exhaust temperature, crankshaft angle, timing, engine rpm, speed, etc. The injectors usually are open only for a few milliseconds at a time. A fuel injector consists of a nozzle and a valve. The power to inject the fuel comes from a Fuel Pump or Pressure Container located far back in the fuel supply.
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