Last updated: June 2026
A failing injector on a Nissan Navara NP300 (D23) 2.3 litre usually shows up as hard starting, a rough idle, smoke and lost power. A genuine replacement injector starts from $760 each at Willys, or from $2,990 for a full set of four, before fitting and ECU coding. Below is how to tell if yours are on the way out, what the job actually costs, and why testing first almost always saves you money.
How much does it cost to replace Nissan Navara NP300 injectors?
At Willys a genuine NP300 injector starts from $760, and a genuine set of four starts from $2,990. The NP300 2.3 litre (D23) is a four-cylinder twin-turbo, so it takes four injectors. Many suppliers charge more again for the same genuine parts, so always check whether you are comparing genuine new injectors against cheaper aftermarket or reconditioned units. Fitting and ECU coding are on top and vary by workshop, so get a quote for your exact build.
A few things move that figure:
- One injector or the full set. Replacing all four at once costs more up front but avoids paying labour and coding twice when the next one fails.
- The high-pressure pump. If the pump is also worn, a genuine NP300 (YS23) high-pressure pump is $1,950. It is worth testing both together.
- Genuine versus aftermarket. Cheap unbranded injectors look cheaper up front but are where most repeat failures come from.
- Coding and labour. Common-rail injectors must be coded to the ECU after fitting, which is part of doing the job properly.
You can check current pricing on the matching parts: the genuine NP300 injector set of four, a single NP300 injector, or the NP300 high-pressure fuel pump.
Signs your NP300 injectors are failing
The common symptoms of a worn or failing injector on an NP300 2.3 litre are:
- Hard or slow starting, especially when cold
- A rough, lumpy or hunting idle
- White, blue or black smoke from the exhaust
- Noticeable power loss or hesitation under load
- Higher fuel use than normal
- A diesel knock or rattle that gets worse as the engine warms
- The engine dropping into limp mode
- Cylinder specific injector fault codes (commonly P0201 through P0204)
- Diesel finding its way into the engine oil, which raises the oil level and thins it out
One leaking or over fuelling injector can cause several of these at once. If you find diesel in the oil, stop driving and get it checked, because fuel dilution can damage the engine quickly.
Why Nissan Navara NP300 injectors fail
Most injector failures on the 2.3 litre come down to fuel quality and wear over time rather than a manufacturing fault. The usual causes are:
- Water or contaminated diesel getting past the filter and eroding the fine internal parts
- A neglected or stretched out fuel filter service interval
- Carbon and deposits building up on the nozzle tips
- Age and high kilometres simply wearing the injector out
Good filtration and sticking to your service intervals is the cheapest injector insurance there is. Regular diesel servicing with the correct filter is the single biggest thing you can do to make injectors and the pump last.
How long do NP300 injectors last?
There is no fixed replacement interval. Injectors are a condition based part, and on a well serviced NP300 they typically last between 150,000 and 200,000 kilometres. Poor fuel, skipped filter changes or a lot of short trips can bring that forward, while clean fuel and on time servicing help them go the distance. Because the range is wide, testing tells you far more than the odometer does.
Should you replace one injector or the whole set?
Start by having all four tested, then decide. If only one injector has failed and the others test well, you can replace the single unit. But if the engine has high kilometres or several injectors are marginal, replacing the full set saves you paying for labour and coding again in a few months. Our diesel injector testing and cleaning service measures each injector against spec so you only replace what actually needs replacing.
Genuine, aftermarket or reconditioned injectors?
We fit genuine injectors. Common-rail injectors are not rebuilt in Australia to a standard we are willing to put our name to, so when an injector fails the test we replace it with a genuine unit to suit your engine and then code it to the ECU. That coding step keeps fuel delivery accurate across all cylinders, and it is not optional on a common-rail diesel. On a job this size, the genuine part is the part you do not want to save money on.
Get your NP300 injectors tested and replaced
We service Nissan Navara owners from our Oxley workshop in Brisbane and our Warana workshop on the Sunshine Coast. If your NP300 is showing any of the signs above, the smart first step is a test, not a guess. Bring it in for injector testing, get a clear answer on what is and is not failing, and a quote to put it right with genuine parts and proper coding.
