December 2020: Safety when changing engine fuel injectors

This update is issued to raise awareness of the potential risk of burns from contact with high temperature water if an injector sleeve pulls free during engine maintenance.

This safety update is for

  • Marine engineers
  • New Zealand commercial operators
  • Maritime NZ maritime officers, investigators and technical advisors.


Engine fuel injector

A fuel injector sprays fuel into an engine as a fine mist at high pressure to optimise combustion and efficiency. The operation of the fuel injector is kept cool by a water cooling system. This water increases in temperature as it cools the engine and can reach very high temperatures.

The injector needs to be maintained to work at its optimum level. Removing the fuel injector is standard practice as part of engine maintenance.

The fuel injector valve is commonly housed by a fuel injector sleeve that sits inside the cylinder head.

Fuel Injectors 1
Maritime New Zealand
Fuel injector valve
Fuel Injectors 2
Maritime New Zealand
Fuel injector sleeve

In 2019 an experienced engineer suffered severe scalding to his limbs while carrying out a fuel injector change. When removing the fuel injector valve it seized with the injector sleeve and both parts came out together. This unplanned removal of the sleeve led to high temperature engine cooling water escaping under pressure.

Two possible reasons why an injector sleeve may seize with the injector are:

  1. A lack of sealing contact between fuel injector sealing face and injector sleeve. This can be caused by dirt or deposits on the sealing face during installation or damaged sealing surfaces. Both may lead to a build-up of carbon deposits that will cause the two to seize together.
  2. A loss of interference fit between injector sleeve and cylinder head. This may be due to a mismatch of tolerances for the sleeve and head.


Risk to safety

If the injector sleeve pulls free during engine maintenance this is likely to result in high temperature water from the engine cooling system being released under pressure. This may spray on to the person performing the maintenance task and can cause severe scalding.


What you should do

To make the maintenance of fuel injectors safer, there are a number of steps you can take.

  • Conduct a risk assessment before carrying out routine engine maintenance.
  • Follow the manufacturer’s instructions. These are written with safety in mind for both the engine and the person working with it.
  • Where appropriate, consider the use of additional personal protective equipment such as safety glasses, long rubber gloves and boots. This will give some protection to the person doing the work.
  • Consider isolating all engine cooling systems that flow through the cylinder head.
  • Check the tolerances for injector sleeve and cylinder head. If necessary, ask the manufacturer to supply the tolerances.
  • Use the manufacturer’s lapping tool for reconditioning any sealing surfaces required as part of this maintenance.

If you are unsure, talk to the supplier or manufacturer of your engine.


Importance of isolating cooling systems when changing fuel injectors

By isolating the high temperature cooling water the risk of harm to the person removing the fuel injector valve and to others in or around the area can be reduced. It is recommended that, where possible, the engine cooling system is isolated before removing a fuel injector. The manufacturer’s instruction may require isolation of the cooling system for the individual cylinder head only.

It is recommended that the whole engine cooling system is isolated to reduce the possibility of high temperature water escaping. Appropriate venting of the cooling system when recommissioning can minimise the possibility of air pockets affecting the engines as a result of isolation.


Contact us for more help

If you have any questions about this safety update, please contact our Wellington office.


New Zealand (toll free):
0508 225 522

Tell us what you need help with and remember to include your contact details (email address and phone numbers).