Petrol injector cleaning

Fuel system, and more particularly, injector cleaners encompass a great number of products and systems that range from simple DIY, pour into the fuel tank additives, to complex, purpose built cleaning and testing machines.

Injectors sometimes need to be cleaned because over time they become clogged with fuel residue, which is something like varnish.  This accumulation eventually reduces the flow of fuel through the injector, disrupting its spray pattern and causing driveability problems such as flat spots and hesitations.

Most fuels contain detergents that help keep the fuel system and injectors clean, but sometimes a more severe cleaner is needed to remove long-term accumulations.

Cleaning methods

There are several common methods for cleaning injectors:

  • The most basic is the DIY in-tank additive.  But in-tank cleaners have a couple of limitations. Firstly, their strength, and therefore their ability to remove heavy deposits, is limited by the fact that very aggressive cleaners can damage fuel system components. Secondly, the effectiveness of the process is unknown, as apart from removing and testing, there is no way of checking the injector's flow rate and spray pattern - two of the critical aspects of its operation. 
  • Professional on-car cleaning systems utilise much more aggressive cleaners, however like in-tank cleaners, the outcome may still be uncertain.
  • The most certain method involves removing the injectors for cleaning. This equipment often utilises ultra-sonic cleaning in addition to special cleaning chemicals and can test the injector's flow rate and spray pattern before and after cleaning to confirm serviceability. The disadvantage of such systems is the added labour costs involved in removing and refitting the injectors.

How often should injectors be cleaned?

Some vehicle manufacturers specify definite intervals and provide their own branded injector cleaners. However, for the majority there really is no definite time to clean injectors as it will very much depend on how the car gets used and whether it is a model that is sensitive to the problem. If it’s a model that develops unexplained flat spots or hesitations, dirty injectors may be responsible, but there could be other explanations as well so proper diagnosis is important.

Prevention Vs Cure

Many workshops encourage customers to have such procedures carried out as often as every service as preventative maintenance.  It’s a good source of additional workshop income too.

While there’s no doubt that an effective fuel system cleaner can provide benefits by removing deposits before they become a problem, it’s questionable if, given their often significant cost, their regular use is economically justifiable. For most cars, problems arising from such deposits occur only occasionally, and based on that alone it would be difficult to justify such frequent servicing. Ultimately however it is up to you, as the vehicle's owner, to choose when such servicing is performed, but if you’re being told that your car is due for an injector clean you should ensure that it is listed as a requirement in the vehicle’s service schedule, and not just a recommendation of the servicing dealer.   

Other issues

  • Blocked injectors are not the only cause of driveability problems. An increasingly common problem with later vehicles is the build-up of organic material in the throttle body and intake manifold, and carbon on intake valves and ports - all of which can cause a range of problems that can be difficult to trace. Injector cleaning won’t overcome any of these but there are other processes that can.  Again, proper diagnosis of the problem is vital. 
  • For information on cleaning diesel injectors see our “Diesel injector cleaning” fact sheet.

A word of warning

If you do choose to use a DIY in-tank cleaner, pay particular attention to the instructions for use. While in-tank products may not be particularly strong in the overall scheme of things, many are capable of damaging fuel system components if incorrectly handled.

The final word

If you choose to use off-the-shelf in-tank cleaners occasionally there’s probably little chance of doing any real harm to the vehicle, provided you follow the instructions.  However, the benefits they produce may be difficult to quantify.  

More information

Should you require further assistance please contact our Motoring Advice Service or email us your details now.