There are a few ways that you can clean fuel injectors.
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Preventative maintanance
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On-board rail cleaning
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Ultra-sonic cleaning.
Preventitave maintanance:
The best way to avoid an unneccessary expense is to regularly put some injector cleaner into the fuel tank. Every 5000Km to 10,000Km should be adequate. Don't put it in every second tank like most of the companies recommmend. They are just pushing their product. There is no evidence that I know of that has proved otherwise. The product is usually added to a full tank of fuel or whatever ratio the manufacturers recommend. Do not overdose as the strength may be too strong and it may damage fuel hoses etc. Do not spill any on your paint work, it will take the shine off the clear coat if not removed immediately.
On-Board Rail Cleaning: EFI only
This method is used to clean the injectors while they are still fitted to the engine. This method cannot be performed at home. The device is nothing more than a pressurised can of concentrated injector treatment solution (approx 300ml) that is injected into the fuel rail. The engine is started and runs entirely from the product in the can. To accomplish this the return line to the fuel tank is blocked, the fuel pump disabled and the fuel line into the rail disconnected or blocked. Any combination of these and exactly how it’s done varies from system to system. Basically the pressurised can is replacing the fuel tank and fuel pump. The engine will run at idle for quite some time before the contents of the can are consumed. Apparently by the time the engine stops, the injectors are clean, so it is claimed.
I did use this method on many occasions back in the 80's, because it was the cheapest option for the customer to use in an attempt to clean the injectors. However it has limitations and does not work on stubborn hard varnish deposits that build around the pintle head. It is impossible to determine at the start whether this method will be successful until it is tried. If the customer has never used injector cleaner in the fuel tank and the vehicle has done say 150,000Km or so, then I would not bother with this method, I would go straight for the off board cleaning. On board cleaning also cannot remove any debris that is caught by the basket filters in each injector.
NOTE: CIS systems cannot be cleaned by this method.
Ultra-Sonic Cleaning: Off Board Cleaning
This is much more expensive because the injectors must be removed from the vehicle. Once removed and the injectors are tested, the small basket filters at the injector inlets and the pintle caps are removed and the injector tips are places in a cleaning solution that is bomberded by ultra sound @ 40Khz. Ultra sound will break up the hardest of varishes and allow the varish to be flushed from the injector in the next stage of cleaning. The Injectors are then mounted on a fuel rail and connected electrically to an injector pulser. Basically a small version of the ECU in the car. The injectors are pulsed for about 5 to 10 minutes using a special solution. The injector spray pattern can be observed on each injector during this phase. After the cleaning/flushing phase, the next step is to test volume flow. While the injectors are still connected to the fuel rail they are placed over the top of 100ml capacity glass cylinders incremented by 1ml lines. The injectors are pulsed up at somewhere around the equivalent duration to engine idle. They can be timed or when the first injector fills the cylinder to 100ml. A comparison can now be made between each injectors performance by variation and compared to specifications if available. Any more than 5% variation in flow will need to be corrected by either further cleaning if required or replacing the faulty injector. With the injectors off and the fuel pressure still maintained the injectors are checked for seepage past the pintle head. Once a satisfactory result is obtained the injectors will have new basket filters fitted in the inlets, new pintle caps and seals and then refitted to the engine.
The engine should now run like it should. That is provided the diagnosis was correct to begin with and this would have been apparent in the initial testing of the injectors once they were removed. This method is the only method that is 100% guaranteed to properly service injectors that are suspected of being faulty.
Below is the machine we used to clean EFI injectors off board. If you want your injectors done properly, find a fuel injection specialist in your town that has Ultra-sonic cleaning available and a test rig to check them correctly.
