Fuel Injectors

What are fuel injectors and where are they located?

In order to send fuel to the engine and achieve efficient combustion, modern automobiles use sophisticated fuel injection systems. In the past, carburetors were used to meter out gas to the engine in response to airflow from the throttle. Today, fuel injectors spray fuel into each individual cylinder. This saves gas and produces better combustion. Although fuel injection has been around for a long time as a technology, it has only become common in gasoline-powered cars fairly recently. Diesel engines have used fuel injectors basically from the start. Gasoline-powered airplane engines began using fuel injection early in the twentieth century. Following World War II, hot rodders started replacing carburetors with fuel injectors. Mercedes-Benz used fuel injection in a Formula 1 racer in the 1950s. It adapted the technology to a production sports car, the 300SL, in 1955. The more efficient combustion gave the 300SL great power and speed, propelling it to racing success. 

Still, the allure of speed was not enough to popularize fuel injection over the simpler carburetor. It would take the increasing engine emissions regulations of the 1970s and 1980s to bring fuel injection to the forefront. At first, automakers tried simple single port throttle body injection systems with one or two fuel injectors attached to the throttle body. Throttle body injection worked very similar to carburetion. Fuel was added at the intake manifold. This was not as efficient as later systems, but it did have certain advantages over carburetors. Namely, the throttle body fuel injector could adjust better to different situations. A carburetor may be tuned to give the ideal amount of fuel at a certain engine speed, but may be slightly too lean or too rich at different engine speeds. Since the throttle body fuel injector is electronically controlled, it can give a better air-fuel ratio across the whole band of engine speed. 

There were still more improvements to come, though. Next up were multiport fuel injection (MPFI) systems. These inject fuel above each intake valve. This leads to more fuel being burned in the combustion chamber and less being wasted than in throttle body injection systems. Port injection requires that there to be one injector for each engine cylinder. Earlier port injection systems supplied fuel to all the cylinders at the same time. The fuel would collect at each intake valve for a fraction of a second before entering the combustion chamber. General Motors used one such system called central port fuel injection (CPFI), sometimes called the “spider” injector because of its resemblance to an arachnid.  Fuel would be distributed from a central point down “legs” to poppet valves at each intake valve. The poppet valves would open under pressure and release the fuel at each leg at the same time. The poppet valves tended to become clogged with carbon build up from combustion byproducts. 

Eventually, more advanced, sequential port injection systems came to be. In these systems, each injector is signaled to fire separately, so that each cylinder receives fuel just as the intake valve opens. This results in a more efficient burn than in older multiport systems. 

The most advanced fuel injection system so far is direct fuel injection. In direct injection, fuel is sprayed not into the intake but into the cylinder directly. The fuel doesn’t mix with air until it is in the cylinder which prevents it from condensing. This, again, gives an even more direct burn. Direct injection has long been in use on diesel engines but is becoming increasingly common in gasoline engines. 

In these modern systems, the fuel injectors are electronically controlled valves that spray an extremely fine mist of fuel through the nozzles they are equipped with into the cylinder intake valves at high pressure. They are found mounted into the cylinder head. The injectors receive fuel either from fuel lines or a fuel rail which, in turn, get fuel from the fuel pump. The opening and closing of the injectors is controlled by the engine control module (ECU), the vehicle’s onboard computer. The ECU uses data from the mass air flow sensor, oxygen sensors and other sensors to determine the timing of the fuel injectors. 

How do I know if my fuel injectors need to be replaced?

There are two main problems that can affect fuel injectors. They can develop electrical problems or, more commonly, they can become clogged. An electrical problem can stop the injector from opening and closing with the correct timing. A clog will, obviously, keep the fuel injector from properly spraying fuel. Clogs can result from debris in the fuel, which can indicate a problem elsewhere in your fuel system. The fuel filter is the most likely culprit and should be checked if you are replacing a fuel injector. 

Problems with a fuel injector will keep the related cylinder from receiving the proper amount of gas or diesel fuel. This can decrease engine power and efficiency. You may find that the car or truck struggles to start and to accelerate. Stalling and misfires are also possible. Due to the inefficient combustion that results from a faulty fuel injector, there might be a strong gasoline or diesel fuel odor in the engine compartment after running the vehicle. A failing fuel injector may also cause your check engine light to come on. 

Can I replace a fuel injector myself?

Replacing fuel injectors can be a tough job and will require patience, a good deal of effort, and some caution. It will also require the use of a specialty tool called a fuel injector puller. We would recommend that you be fairly comfortable with engine repairs before replacing your own fuel injectors. It may be wise to take photographs or make drawings and notes of the layout of your fuel injection system before you start taking it apart. 

Remember that the injectors have to spray the fuel at very high pressure in order to turn it into a fine mist. The high pressure fuel can pose some risk. Before removing the fuel injectors, you’ll want to take the pressure out of the system. You can do this by disconnecting power from the fuel pump and then idling the engine. This will drop pressure in the fuel lines. Then you can safely remove the fuel injectors.  

Depending on the layout of your engine, the injectors may be fairly easy to access or they may be underneath other parts—like the intake manifold. You will have to remove any parts that are in the way. Then, if you have a fuel rail, which the large majority of vehicles will by and large, you’ll have to disconnect the fuel line from it, unbolt it, and pull it off the injectors. Otherwise, you’ll have to separate the individual fuel lines from the injectors. Then, disconnect the wiring harnesses from the fuel injectors. Then, use the fuel injector puller to firmly but carefully pull out the injectors.  Any damage you do to the cylinder head can cause further problems down the line, so it really does pay to be careful here. Also be sure not to let any debris into the engine while the injectors’ mounting holes are open. At this point, you can reverse these steps to install the replacement fuel injectors. 

Need a fuel injector replacement?

One of the most important factors for ensuring that your engine runs efficiently is the system by which gas or diesel fuel is delivered to the engine. One of the major parts of a vehicle’s fuel system is the fuel injector. Fuel injectors are responsible for delivering just the right amount of fuel to mix with air in your engine's combustion chamber in order to achieve optimum fuel combustion. This pressurized gas or diesel fuel is necessary to keep your car or truck’s engine running at its peak operating performance. If a fuel injector has been damaged, then it will not be able to spray the needed fuel into the cylinder intake valves properly, which ultimately will create an imbalance in the air/fuel mixture. This can lead to a myriad of problems, such as stalling and issues with starting and accelerating—just to name a few, so it’s imperative to obtain a fuel injector replacement as soon as possible if it is malfunctioning.

At 1A Auto, we carry aftermarket fuel injectors for many makes and models, and at great prices. Our fuel injectors are brand new, not remanufactured, and factory tested prior to shipment. They are made to factory specifications to be a direct replacement with the correct electric plugs as the originals. We also make shopping for replacement fuel injectors for your car, truck, SUV or van easy at 1A Auto—we're here to help you select the right part for your vehicle! Call our customer service toll free at 888-844-3393 if you have any questions about our products, warranty, compatibility or to purchase, or you can buy online.