Diesel Injector Nozzle Calibration . Toyota L Engine Guide

Diesel Injector Nozzle Calibration

Diesel injector nozzle calibration is necessary when your car is an old model that had been used for decades because parts have passed through heat over time and may have weakened, or have perforations.

Diesel injector nozzle calibration-injector


This service is also needed in modern cars which are digitally equipped but may have encountered fault in a program that feeds the wrong message to parts that perform the measurement of the right amount of fuel for the engine.

Why calibrate injectors?
A fuel injector is an assembly or group of parts assembled and otherwise called a nozzle. Sometimes the whole thing is called the nozzle and the end part of the injector where the fuel comes out is also called a nozzle.

The function of the injector is to control the flow of fuel through the injection nozzle to the combustion chamber.

On the passage of time, one of the parts may have weakened or had perforations and for that reason, the right amount of fuel to be supplied to each cylinder is no longer normal causing more emission of smoke undesirably affecting anyone around.

The primary reason why injectors are calibrated is to bring it back to the original pressure that supplies the right amount of fuel to the cylinder for efficient performance.

How is Calibration Done?
This should be done by a professional technician unless you have the devices to use and you know the proper pressure.

The reason is that calibration is not just cleaning the injectors but it is to check the pressure and if it is not in the desired one it should be put back to the original pressures.

Why has the pressure possibly changed?  There are two reasons that contribute to this state, the nozzle spring and the injection nozzle.

Diesel injector nozzle calibration-nozzle spring

Diesel Injector Nozzle Calibration-Nozzle

As I have said there are parts that may in due time weakens or perforated because of heat.

If the nozzle spring has weakened the pressure has loosened and more fuel is sprayed to the cylinder.  The remedy is to change the shims to a thicker to add pressure to the spring.

If there are perforations on the nozzle or the nozzle needle there is no other remedy than to replace the injector. You cannot control the flow of the fuel by adding shims to add pressure to the spring.


Disassembled Diesel Injector

Diesel injector nozzle calibration-disassembled injectorDiesel injector nozzle calibration-disassembled injectorDiesel injector nozzle calibration-disassembled injectorDiesel injector nozzle calibration-nozzle cleaning

Possible Symptoms when Diesel Injector needs calibration

Black smoke-this is a sign that fuel is over to the limit needed by the engine for combustion.  Not all fuel is being burned and so it is wasted and emitted outside. If smoke is white oil is passing somewhere the cylinder or cylinder head gasket and is mixed with the fuel in the combustion chamber.


The Nozzle Tested on a Pressure Gauge of 125 Pounds Per Square Inch (PSI)

Rough Engine Idle

Assuming that you have fixed all the proper idle speed, no vacuum leaks, no damaged or incorrect spark plug gaps (for the four-stroke engines), you have calibrated your fuel injection pump but the idle is still rough it’s time for you to have your fuel injector calibrated.



8 thoughts on “Diesel Injector Nozzle Calibration”

  1. toyota L is not suitable to used for passenger jeep, what is the reason or problem if use this type of engine to passenger jeep.And i experience to my engine toyota L in starting specially in the morning the engine rattle but if reached the temp. in a hot it will become smooth.

    • You are right Anthony, the Toyota L engine is not designed for passenger jeep but many shops do the convertion. Consider the following for inspection and cleaning: Fuel filter, if you are sure the injection pump is working well, the nozzles might need cleaning or calibration, or you have to change oil for it may have the viscosity problem.

  2. Hi
    Wow what a great post. I have so many problems with cars. It seems like you have some very good answers for me. Like if my car was to start having black smoke it could be time to have the diesel injector needs to be calibrated. Thank you a lot of great advice here.

    • Thank you, Melissa, for dropping a comment on this post. That is one of the ways but there could be more like Injection Pump Calibration. Recently I did this to resolve the long issue of thick smoke emission. Now I’m proud to use my old car because the smoke is already gone. I thought I can help patronize clean air act and environmental protection program of any government.

  3. Many thanks for the highlight. I drifted into this site while looking for a solution to my Toyota hilux single cab, 2010 model, driven by D4D engine 2KD, 2494 cc. It has a fabulous one kick start by struggles to move and make some rattle sound, but gains thereafter( I imagine it could be because of the Turbo charge). No black smoke is produced though, only the weakness at take of. What is your opinion in this?

    • Fredrick, I think your suspicion is possible. Try to inspect your engine oil the turbocharger might be lacking oil supply. If you are sure the turbocharger is fine then the problem comes from other causes.

      Thank you for trusting my site, I hope you will come back for an update on the issue and let’s learn together from your experience.

    • Fred check your fuel pump, common rail sensor and your padel/acceleration switch. The other probelm might be faulty/blocked EGR valve.


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