A Complete Buying Guide for Car Fuel Injectors

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A Complete Buying Guide for Car Fuel Injectors

Automotive fuel injection systems began replacing carburettors on most stock production vehicles in the late 1970s and early 1980s. Although a few models boasted earlier petrol injection systems, the technology was expensive and impractical for most manufacturers. Fuel injectors operate much more efficiently than do carburettors and produce less exhaust emission; thus, with increased demand for cleaner, more economical vehicles, manufacturers began investing in the new technology. Consumers are often confused by the terminology associated with the different types of fuel injection systems. Some automobile enthusiasts replace the carburettors on older vehicles with petrol injection systems, while many drivers just want a better understanding of what goes on under the hood when it comes to burning petrol.

One can purchase fuel injection parts at auto parts suppliers and specialty automotive retailers as well as online. Sellers on eBay offer a good selection of both new and used fuel injection parts. Knowing what to look for when it comes to injection systems can help buyers determine the specific part that meets their needs.

The Basics of Fuel Injection

Internal combustion engines run on a mixture of air and petrol. Carburettors used to be the means of combining the air and petrol, which then passed through a throttle plate into the engine's intake manifold where is was delivered to the combustion chamber of each cylinder. The mixture could be adjusted somewhat but the design of the carburettor meant fuel was essentially dumped into the intake and the suction of the engine's intake stroke pulled the fuel to the cylinders. With the advent of fuel injection, engineers replaced the carburettor with one or more injectors that spray a more precise and controlled amount of petrol, helping to improve the efficiency of the engine.

Types of Fuel Injection

How well the fuel injections manage the flow of petrol through the engine depends on the design of the injection system itself. There are several different types of injection systems, each a little more advanced than the previous version. It is helpful for consumers to know the difference and the basics of the type of injection system on their vehicle, as they require different levels of maintenance when something is amiss on the engine.

Single Port Injection

Often called throttle body injection on American models, a single port injection (SPI) system has one injector located over the throttle plate ahead of the intake manifold. SPI is similar to the carburettor, in that the fuel is still dumped in one place for induction through the ports of the intake, but with some distinct advantages over a carbureted system. The biggest advantage of the injector is that it can more precisely deliver the exact amount of fuel the engine needs based on throttle pressure. Additionally, the injector can create a finer mist pattern than the jets of a carburettor, which better atomises the fuel. Problems can arise with a SPI system: when the injector partially clogs it restricts the spray pattern, and dripping fuel results in less efficient operation. Injectors need periodic cleaning and the occasional replacement when they become worn out or experience an internal failure.

Multi Port Injection

With a multi port injection (MPI) system, an injector is devoted to each cylinder on the engine. The location of the injector places it in a position on the intake manifold where it can deliver a burst of petrol at the mouth of the cylinder's intake valve, with the timing of the fuel delivery coinciding with the opening of the cylinder's intake valve. Air is still brought into the intake but it does not mix with the petrol until just before entering the combustion chamber of the cylinder. The advantages of MPI are that less fuel goes unburnt, reducing fuel waste; decreased emissions from unburnt fuel; and less carbon deposits in the engine. Control of the fuel delivery system is not dependent solely on throttle pressure. MPI vehicles are equipped with an Electronic Control Unit (ECU), which monitors throttle pressure and a number of other engine components by way of a system of sensors; fuel delivery is calculated in a more precise manner given the input the ECU receives.

Direct Injection Systems

The most efficient and cleanest-burning engines employ the use of direct injection of petrol into the combustion chamber itself. The intake valve opens to allow the air in and the injector sprays as the compression stroke commences. Direct injection systems provide improved fuel atomisation, maximum efficiency, and minimal emissions, as well as significantly reducing carbon deposits on internal engine components. With the input from engine sensors, the ECU can squeeze the most performance out of every drop of petrol without sacrificing performance for the sake of fuel economy.

Advantages and Disadvantages of Different Injection Systems

Each different type of petrol delivery system has its advantages and disadvantages, and understanding these characteristics helps consumers make informed decisions when considering fuel injection systems. By comparing the different basic types of injection systems it is easier to see the differences. The following chart shows the progression on engineering designs, starting with the carburettor and finishing with direct injection.

Fuel Delivery Method




Petrol mixture can be freely adjusted

Most inefficient system, hard to adjust for economical operation

Single Port Injection

Better control of petrol delivery, more precise fuel atomisation

Still dumps petrol into intake and relies on air induction for delivery, only slightly improves emissions

Multi Port Injection

Delivers petrol directly to intake valves, improves efficiency, reduces carbon emissions

Some fuel remains unburned and collects carbon in intake and on valves

Direct Injection

Delivers petrol directly to cylinder combustion chamber for maximum efficiency and minimal emissions

Repair costs generally higher than other, simpler types of fuel delivery systems

With regard to emissions and fuel economy, carburettors and SPI systems provide more fuel into the cylinders than the engine can properly burn; excess fuel robs efficiency and causes the engine to not run cleanly. If the air fuel mixture contains too much petrol when it passes through the intake, it is possible for some molecules to not make it into the combustion chamber; occasionally this occurs with MPI. When fuel is not burned it also can result in carbon deposits forming in the engine. Direct injection eliminates these issues when all components are functioning properly. Failures or malfunctions with direct injection are not limited to problems with injectors; sensors, ECUs, and electrical resistance issues can all cause fuel economy to dip and emissions to rise.

Fuel Injector Maintenance

An often overlooked part of fuel injector maintenance is keeping the vehicle's air and petrol filters clean. One should replace the petrol filter annually, check the air filter periodically, and replace as needed. Periodic injector cleaning can help to keep injectors function properly and is highly recommended for older, high-mileage vehicles. There are three primary methods of fuel injector cleaning.

In-Tank Fuel Additives

Injectors can be cleaned by pouring a petrol additive to the fuel tank. New vehicles do not need to be treated frequently; one or two applications per year are sufficient. Older vehicles benefit from petrol additives every few thousand miles.

Pressurized Injector Cleaning

Pressurized injector cleaning involves inducing injector cleaner directly into the fuel line just before the injectors. This type of cleaning allows a more concentrated solution to be directed through the injector instead of being diluted by the petrol in the tank. Pressurized cleaning requires specialised equipment and is usually performed at auto repair shops.

Off Car Injector Cleaning

Injectors can be removed from the vehicle and placed in a cleaning machine that also acts as a diagnostic tool for identifying problem injectors. This is a relatively expensive procedure and is usually performed for diagnostic reasons as opposed to regular maintenance.

Buying Fuel Injector Components on eBay

One can purchase fuel injection parts, assemblies, and maintenance supplies from sellers on eBay. Buyers who need a specific fuel injection part can use the eBay Motors parts search tool to find parts for the exact make and model of vehicle that they own. Simply enter the vehicle's make and model in the drop-down selection boxes, enter the name of the part you are looking for, and click search. All items matching the selected criteria will be displayed. Sellers also offer injector cleaning supplies, which buyers can purchase from online eBay Stores.

Shopping on eBay is convenient; buyers browse listings, select the items they need, and have the product shipped directly to their home. Buyers can deal confidently with an eBay seller by examining the seller's feedback ratings; buyers who have purchased merchandise rate sellers on their satisfaction with the manner in which transaction was handled. Buyers can safely and securely transfer funds to an eBay seller by using PayPal to complete the purchase.


Fuel injection systems are an engineering advancement that vehicle owners recognise as a big improvement in the method of fuel delivery to the engine. Drivers appreciate the added performance provided by fuel injection and value the fact that they can get the improved throttle response without sacrificing fuel economy. Everyone benefits from the reduction in vehicle emissions, thanks to cleaner running engines that utilise fuel injection to reduce pollutants.

Whether buyers are looking to convert an existing vehicle to fuel injection or considering purchasing a new- or late-model used car, it helps to know the differences in the various types of fuel delivery systems. Car buyers comparing vehicles can select the vehicle with the fuel injection system that provides the most benefits to them in accordance with the available budget. Component and parts buyers need to know the specific system they are working on, as most parts for a SPI do not interchange with an MPI system.

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