Injector servicing & cleaning

What is an injector ?

An injector is a solenoid valve, it receives pressurized fuel and delivers it in the intake pipe as a spray, as required for a good combustion. The opening of the injector occurs during a very precise time determined by the ECU during the engine cycle, computed from the sensors data.


The fuel injectors are precision equipment parts, with strict manufacturing tolerances. They are also sensitive parts that must be maintained in good working conditions, as well as the whole fuel supply line.

What issues may have the injectors ?

If the injectors are losing their ability to fulfill their job, a number of symptoms will appear :
• Engine will not fire.
• Engine firing is difficult, especially when hot.
• Detonation (knocking or pinging), causing possible engine damage.
• Rough, irregular idle.
• Light throttle surging or bucking.
• Low speed hesitation and surging issues.
• Loss of performance.
• Increased fuel consumption.
• Emission problems.
• Fuel leaks.

Among the causes responsible for these symptoms:
• Faulty injectors.
• Blocked injectors.
• Dirty, clogged or worn injectors.
• Clogged injectors.

Faulty injectors

Symptoms : no start, or only one cylinder fires, depending on the extent of the problem.
This is caused by an electrical problem with a connector or a faulty injector solenoid.
To check this, go to DIAG Mode #36-37, after disconnecting the fuel pump.
If nothing happens (no operating noise), check the connectors.
Check then the resistance of the coil inside the injector : resistance must be 12 Ω (10% tolerance).
If this resistance is infinite or zero, the injector is faulty and must be replaced.
If the resistance is correct, the injector might be blocked.

Blocked injectors

Symptoms: no start, or a single cylinder works, depending on the extent of the problem.
An injector may stay open. In this case, there will be a fuel leak easy to detect.
It can also stay closed. In this case nothing happens.
This blockage is usually caused by a wax deposit inside the injector that must be cleaned to unlock.

Dirty, worn injectors

Symptoms: Firing is difficult, power loss, increased consumption.
It may appears after a high mileage (+ 100.000km).
The injectors must be cleaned or replaced.
Check also the state of the O-rings and replace if worn, cracked, cut.

Clogged injectors - partially or completely

Symptoms: Firing is difficult, power loss, increased consumption.
Caused by rust particles from the tank or wax deposits due to poor fuel quality. The fuel spray is not correct, the motor will not function normally.
The injectors must be cleaned.

TDM injectors

(image)Section of the TDM injector :
A - Fuel intake, with a fuel filter.
1 - Coil
2 - Core.
3 - Spacer.
4 - Needle.
5 - four-hole type injection orifice.

The injectors are made by Nippon Denso. These are "high impedance" type injectors.
Specifications :
• Reference : Nippon-Denso 195500-3830
• Impedance : 13.8 Ω
• Flow rate : 176 cc/min (17.3 lb/h)
• Fuel pressure : 290 kPa

These injectors are quite expensive to replace (€180 each), to compare to a simple yet thoughtful cleaning to restore the original characteristics at a far lower expense.

Injector cleaners

Off the shelf injector cleaners are very common. You may find them in specialized shops. These products are intended to be poured into the fuel tank and they are expected to produce a thorough cleaning of the entire fuel supply line while driving, resulting in improved performance.

Reality is different : these products are too diluted to offer anything but preventive action. They work not long enough and pressure is not high enough to act effectively. In addition, since they work on the entire fuel supply line, the wax deposits, dirt, rust particles upstream in the pipes may be detached and go to the injectors and accumulate there, which will worsen the problem ! Like most of the fuel additives, they are especially designed to be easy to use to the greatest number. They are actually preventive and not curative products.

Injectors are very precise pieces of equipment, they are more difficult to maintain than just pour some liquid inside the fuel tank and drive. When dysfunction symptoms begin to appear, it is too late to start a preventive action, only a curative action will fix the issue, that is to say the removal and cleaning.

There are many review around that test the effectiveness of these injector cleaners, they are most often done for commercial purposes. Result always seems too good to be true ! Anyway, none of these products even the best ones can compete in efficiency with effective cleaning methods.

Cleaning by a professional

It is possible to give the injectors to clean by a professional. The cost is much lower than a replacement. There are mainly two way to clean injectors :

• Cleaning may be done without removing the injectors from the engine. Injectors are then fed one by one by a pressurized cleaning fluid from a separate tank while the engine is running. The result is still pretty average as the working pressure and time remain standard. There is also a problem with the cleaning fluid as it goes inside the cylinders and participates in the combustion process : the engine/ECU and exhaust/catalyst system may not appreciate !

• Cleaning may be done after removing the injectors from the engine. They are then cleaned inside an ultrasonic cleaning tank while simulating the operation of the injectors with a pulse generator and a cleaning fluid pump. This is the most effective cleaning method and it also allows to check the spray shape from the injectors outlets.

Cleaning at home

Cleaning injectors is not so difficult to do, it may be done with simple tools and some knowledge - and also some safety precautions.

Required materials

• Carburetor cleaning spray, or cleaning fluid in bottle if you own a compressor (a bit more complicated).
• A standard syringe - 5ml model - it is not very imperative.
• Tubes, hoses and other conical caps from sealant cartridges.
• A pipe clamp collar, due to the pressure involved.
• A 12 volt source such as a power supply or a battery.
• Some wiring and a pushbutton.
• O-rings, size 8 x 11.8 x 1.9, reference 6A.
• Gloves and safety glasses.


• First, pressure cleaning should be done in reverse direction. This allows to easily evacuate the trapped particles : dust, rust and mostly wax.
• Then apply the cleaning in the normal direction.
• The body of the syringe serves as a pressure buffer tank.
• The tubes used to adapt the diameter of the pipes between the syringe and the injector.
• The push button allows to easily control the opening of the injector.
• Do not operate the injector permanently. The coil may overheat and deteriorate if there is no fuel passage or cleaner to cool it.

If a standard cleaning fluid and a compressor are used, get a small polypropylene bottle in place of the syringe, with a greater capacity to avoid having to refill it frequently.
Before the pressure cleaning, an internal soaking of the injectors is highly advised. Leave it at least an hour, protect the top opening to prevent evaporation.


To access the injectors :
• Remove the seat.
• Remove the fairing sides.
• Remove the two small black side covers.
• Remove the two screws securing the tank to the front.
• Move the tank back up to get enought room, secure with a strap.
• Remove the air filter casing. It is possible to access the injector with the casing on, but the operation becomes more complicated.

Warning : the fuel supply rail and the fuel supply hose are filled with pressurized fuel. Although the fuel quantity is small and the pressure is low, it is best to take some precautions :
• Disconnect the fuel pump.
• Go to DIAG mode #36 or #37 and activate it several times to drop the fuel pressure.
• You may also start the engine and wait until it dies.
• Disconnect the fuel supply hose from the fuel rail, get a rag ready for fuel leaks.

Removing the injectors

(image)• Remove the two screws securing the fuel rail.
Note : these screws have a JIS footprint, do not use a Phillips screwdriver as it will cam out and damage the head. If they are too tight - they actually are - use a shock screwdriver - that's what I did.
• Recover both spacers before they get lost in inaccessible places !

(the second screw is hidden under the hose on the pic)

(image)• Pull the fuel rail strait to extract the injectors from the throttle body
• Remove the injectors from the fuel rail, recover all seals : one seal and an o-ring on top side, one seal on the bottom side - the latter usually stays on the throttle body
• Disconnect the injectors, be careful while handling them : do not touch the bottom side where the injector nozzles are located.

(image)• The two injectors are ready for the next step.

Setting-up the hoses

(image)• The 5ml syringe has a more suitable diameter. Remove the piston and cut off the top. Bevel the cannula, this allows to shove it more easily into the syringe. Insert the syringe onto the hose and the hose on the injector outlet nozzle side.

(image)• Connect the power supply and the push button. The polarity does not matter.
• Check that the injector is working properly by pressing the push button.

(image)• Secure the hose with a hose clamp. At first I did not do it because the hose seemed tight enough, but it was not and the syringe flew away !

(image)• Connect the cannula to the spray bottle.

Cleaning the injector

(image)• Wear gloves and eye protection
• First fill up the syringe with the spray bottle up to one-third.
• Press the push-button repeatedly until no more liquid remains inside the syringe.
• Repeat the operation several times.

(image)• Do the same in the normal direction of operation of the injector, it must then deliver a nice uniform and regular spray output. If this were not the case, restart operations.

• While you're at it, clean the fuel rail too.

Replace the injectors

(image)• Replace the seals on the injectors, use new O-rings.
• Lightly lubricate the O-rings with engine oil before engaging the injectors on the fuel rail, otherwise they may be destroyed.
• Engage the injectors gently, help with some twists.
• Plug-in the connectors.
• Install the full fuel rail on the intake ducts while driving the injectors inside the throttle body.
• In case you replace the JIS screws with two Hexa 5x60, the one on the LHS should be shorten at the same length of the JIS one otherwise it will exceed the thread and block on the throttle body below.

All done, time to clean the fuel tank, the fuel pump and the fuel hose !

My personal experience

The problem appeared after using a poor quality fuel : too old, tank bottom, water contamination, etc. I'm not sure what exactly was the problem with the fuel. Current modern fuels degrade quickly, especially if they contain methanol - it also absorbs moisture from the air. A real disaster !

The symptom : engine will not start, it coughs then stops. The ignition system is working fine. No error code on the dash.

After a check with DIAG mode that revealed nothing, I checked the firing with a cloth soaked in acetone on the intake duct : the engine fires ok. Conclusion : there is a fueling problem.

So I tested the fuel pump (DIAG #09), the fuel pressure regulator, then the injectors (DIAG #36-#37), everything looks normal, there is some fuel going from the injectors. Unfortunately the spray pattern is not correct, or there is simply not enough fuel. Injectors cleaning seems a must go. Naturally I also cleaned the fuel tank and the fuel pump, otherwise the problem would start again soon !

The end of the story : after reassembling, I did some tests in DIAG mode and then an engine firing test : all went well at the first try. A short tour latter, the engine is behaving better than before - I mean before the issue, more reactive, better acceleration, best overall behavior.
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