How to replace a Diesel Injector Nozzle

This section shows how to replace an Injector nozzle. This can be successfully completed on all makes and types of diesel injectors. However this is NOT suitable for Common Rail injectors.


These Instructions are for your guidance only and any repair work carried out is at the risk of the repairer. 

Prior to removing the Injectors, thoroughly clean the area you are working on.

As each injector pipe is removed from the Injector, fit the plastic cap supplied over the Injector inlet to eliminate contamination. Leave these caps on until Injectors have been cleaned.

Once removed from the engine the injectors can be cleaned with a wire brush and washed in a light oil solution.


Nozzle replaceable. Not advisable to remove pressure adjusting cap unless you have access to a Injector pressure tester

Nozzle replaceable. All components can be removed for cleaning.

These are all of the components from an Injector.


Carefully remove the injector nozzle cap nut, remove and inspect the old nozzle. If fuel contamination is suspected as cause of failure (needle seizure) then this must be addressed before installing serviced Injector.

The carbon deposit in and around the nozzle retaining cap nut can be removed with a wire brush, washed and blown off with an air line.

Wash the nozzle sealing face on the Injector body, blow across the face with an air line and inspect for damage. Also inspect for any damage to the nozzle locating dowels where fitted.

Remove the plastic cap from the Injector inlet connection and blow through the Injector with an air line, and immediately refit the protective cap.

Following cleaning blow compressed air through body to remove any debris. Refit the plastic protective cap.

The compressed air should be directed via the Injector inlet connection.

An erosion line may be visible on the intermediate plate.

A couple of minutes hand lapping on wetordry (P900 grade) will soon erase this problem. Good idea is to use a sheet of lightly oiled wetordry on a piece of glass, this will ensure the plate is perfectly flat.

Your new nozzle is now ready for fitting.

Unpack the new nozzle being careful to keep the needle inside the nozzle (match fit).

Wash the nozzle and needle in a light oil solution and ensure the needle moves freely within the nozzle.

Fit the new nozzle ensuring to align the relevant holes with the locating dowels (where fitted).

There will be a gap between the nozzle face and body, this is normal as there is spring tension against the nozzle needle, refit the nozzle cap nut. Torque values depends on application and can be obtained from this site, however a typicle torque value for a screw in type injector is around 90Nm.
The Injector can now be ‘pop’ tested at your local DFI workshop and the pressures set to manufacturer’s specification. They normally make a nominal charge of a few pounds for this service.

Alternatively you may decide to refit the Injector (pressure will not deviate far from the original setting). The choice is entirely yours.
Refit Injector but prior to removing protective cap, clean around the high pressure Injector pipe nut and olive, Crank engine until fuel is injected from all of the pipes thus ensuring we have complete cleanliness when reconnecting the high pressure pipe to the Injector.

 * Relates to Injectors where a pressure adjusting screw is used, rather than the more commonly used pressure adjusting shim.

When installing the new nozzle there will be a gap, this is quite normal as the nozzle needle will be in contact with the pressure spindle under spring load.

Ensure locating holes are aligned and fit over the two Injector dowels.

Finally fit seat washer and protective cap over nozzle until the Injector is ready for use. Only remove the protective cap from the inlet connection after installation into the engine and following cleaning of the pipe connections.

Dave Sofio 21.02.2022 14:06

I'm finding injectors for my engine (Isuzu 4JB1T) online for $30-$40 each. But to get the 'correct' p/n? $300 EACH. Can I "make" 'em by re-using my OK nozzles?

Per 26.07.2021 11:30

"Torque values depends on application and can be obtained from this site"

Where do I obtain these values on this site?

-Thanks for a nice site!

Mr Martin Thomson 08.03.2019 14:44

Looking for nozzles for 059130277AH. Can you help?

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