As technology advances, features that started out as being cutting-edge become the norm. Fuel injection was often seen on high-performance and luxury cars from as early as 1940, but it wasn’t until the late 90s that every run-of-the-mill vehicle used it. 

So why the change? We’ll take a look at what fuel injection is, why it's used, signs to look out for if yours is failing and, crucially, how much a fuel injector replacement costs in the UK for various cars and models. 

What is a fuel injector? 

The clue is very much in the name, it’s a device that directly injects petrol or diesel into the combustion chamber. Fuel injectors use electricity to add the precise amount of fuel needed at every engine cycle.  

Located on the top of the engine, the tops and fuel pipes are rarely visible without removing the engine covers and other components. They protrude into the engine's cylinders, similar to spark plugs. 

Fuel injectors replaced carburettors. Being controlled by the  fin, fuel injection systems allow for more precise fuel delivery, leading to both better fuel economy and more power. 

Using a magnetic coil, similar to an electronic valve, fuel is forced through a small orifice, this allows very precise control of both the timing and capacity of the injection process.  

What is an injector seal?

The injector seal and O-ring are crucial to the proper functioning of fuel injectors, they form a tight seal around the injectors making sure no fuel vapour leaks out, and no air is able to get it in. 

How much does a replacement fuel injector cost in the UK? 

The average cost of replacing a fuel injector in the UK is from £120 to £160.  

However, the actual cost will depend on three factors: how many your car has, what type of car you have, and where in the country you are located. The table below shows the price guides or replacement fuel injectors for various manufacturers.   

• Ford: £120 - £160
• Vauxhall: £120 - £160
• Volkswagen: £130 - £170
• BMW: £130 - £190
• Audi: £130 - £170
• Toyota: £130 - £160
• Nissan: £115 - £130
• Mercedes: £140 - £160
• Peugeot: £95 - £140
• Renault: £100 - £160
• Honda: £120 - £150
• Citroen: £90 - £130
• Hyundai: £100 - £130
• Land Rover: £150 - £190 

What causes fuel injectors to fail? 

Fuel Injectors are complex and intricate components, there are a few ways an injector can become defective, most commonly either due to contaminant buildup or seals ageing and cracking.  

Fuel contains trace elements of impurities such as carbon, these can get trapped inside the injector over time, and cause issues preventing the injector from opening or closing, both resulting in running problems. 

Time is not kind to any component with rubber seals, these will gradually dry out and begin to be less effective. Injectors have multiple seals, inside and sealing to the engine, and they can begin to leak over time. 

Poor fuel filtration 

Cars are fitted with a fuel filter, which stops any larger particles that may have been transferred into the liquid through transport and storage.

If your filter is particularly old or of inferior quality, it may allow more contaminants to enter the fuel system. The fuel injectors will always respond poorly to fuel with contaminants. 

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How long do fuel injectors last? 

Typically fuel injectors should last between 60,000 and 100,000 miles. This may be less if the car has been left unused for large periods of time because the seals in the injectors will age faster if not used. 

There are some factors that affect the lifespan of a fuel injector, such as fuel quality, fuel filter replacement routines and the type of vehicle. 

Injector seals replacement cost 

The actual cost of an injector seal replacement is very affordable, at only a few pounds. However it is the knowledge and mechanical experience needed to change the seal which causes the cost to go up, you will likely need a professional mechanic to change the seal which will cost labour time.

Does supermarket fuel cause injector issues? 

It is commonly stated that supermarket fuels are of inferior quality to ‘branded’ fuels from the likes of Shell or BP petrol stations. This is often touted as a reason for poor running, lower MPG and issues with engines. 

The fact that supermarket fuel is often around 5p per litre cheaper than branded fuels often adds to this theory.  

In reality, there is no evidence that supermarket fuels are in any way inferior to petrol or diesel from name-brand garages, as found in this article by Which. 

From this evidence, we would say there is little chance that supermarket fuels cause increased wear or defects with fuel injection systems. 

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

Because the injectors undertake such an important role in an internal combustion engine, the symptoms of a failing or faulty injector can be very prominent. The issue however is that many of the symptoms could be caused by other faults. 

Rough idling 

When the engine is idling, the fuel injectors are only spraying a very small amount of fuel per cycle, if your engine feels particularly lumpy at idle, or stalls when idling, it may be that the injectors are partially blocked. 

Stalling on acceleration 

IF your engine stalls when trying to accelerate or rev the engine, this usually indicates a lack of fueling, this could be caused by a faulty fuel pump, blocked fuel filter or broken injectors. 

Poor MPG and power 

As the engine's power is directly related to how much fuel is injected, if the injectors are blocked, or not delivering enough fuel, the engine will be significantly down on power.  

Another telltale sign of bad injectors is a reduction in efficiency, this can be caused by over-fueling when injectors do not close properly after cycling. 

Can injectors be cleaned without removing them? 

Modern cars are extremely complex, and the engine bays often have multiple covers and other components on top of the actual engine. This combined with how delicate the injectors are, removing them can be costly. 

There are a few different products available that can help to clean your injectors without the need to remove them.  

Products such as Redex, use speciality solvents added as a liquid to your fuel tank to help dissolve built-up carbon and other deposits from the fuelling system. 

Tests have shown that these can help with minor injector problems, but it’s probably best to consult your mechanic first. 

Can E10 fuel cause injector issues? 

As we discussed in our E10 fuel article, since September 2021 the standard for petrol sold in the UK has changed, whereas previously it contained 5% ethanol, it now contains 10% ethanol. 

This can have notable implications for older cars, where the rubber and metals used in the fuel system can be degraded prematurely by higher levels of ethanol. 

Fuel injectors use multiple metal and rubber components so it may be the case that more issues with injectors will be experienced if E10 petrol is used, but there is no concrete evidence to support this.  

Our advice would be to use the government checker and follow any advice this gives, even if the extra ethanol does not affect your injectors, it may well cause issues with your fuel system if it is over a certain age. 

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