Importance of Fuel Injector Cleaning

I am initiating this thread with the hope that it will enhance awareness among Pakwheelers about importance of fuel injector cleaning. I went through many threads of Pakwheels and gathered that people need injector cleaning but they are not aware how is it done, what are its benefits and what are the risks in driving vehicles with clogged injectors. It is very important to have your injectors delivering precise amount of fuel with specific spray pattern to keep your vehicle moving on its optimum capability. Fuel injectors have somewhat the same importance for our car engine as arteries in our own body.

I, being a fuel injection professional, would be pleased to respond to queries and concerns in this forum. I also expect valuable input from knowledgeable members of the site which will enlighten us more on the topic.

As a beginning I give below an adaptation from article written by Larry Carley an internationally well-known automotive technical writer, which unveils the importance of clean injectors, why we need to get the injectors cleaned, different methods of injector cleaning with their effectiveness and shortcomings.

Clean fuel injectors are a must for peak engine performance, fuel economy and emissions. If the injectors are dirty and can't deliver their normal dose of fuel, performance, fuel economy and emissions are all going to suffer. Dirty injectors can't flow as much fuel as clean ones, nor can they deliver the correct spray pattern that is so essential for clean, efficient combustion. The fuel feedback control system will compensate for the leaning effect once it is in closed loop, but it can't correct the underlying condition that is causing the problem.

The injectors need to be cleaned, if an engine is experiencing any of the classic symptoms of dirty injectors, such as lean misfire, rough idle, hesitation and stumbling on light acceleration, a loss of power, and higher hydrocarbon (HC) and carbon monoxide (CO) emissions.

Lean misfire may also trigger a misfire code and turn on the Check Engine light on 1996 and newer vehicles with OBD II systems. The code often will be a P0300 random misfire code, or you may find one or more misfire codes for individual cylinders, depending on which injectors are most affected.

FUEL INJECTOR CLOGGING
All vehicles are vulnerable to injector clogging, but the ones that are most vulnerable and most likely to experience such driveability and emissions problems are ones with pintle-style multiport injectors.
In the early pintle-style injectors, the nozzle's shape and orifice size determine how much fuel flows through the injector and the shape of the spray pattern. Most pintle-style injectors are designed to produce a cone-shaped spray pattern. But, if fuel deposits accumulate in the nozzle area, it can restrict fuel delivery and break up the spray pattern, causing a lean fuel condition and many of the problems just mentioned.

Where do the deposits come from? Mostly from the fuel itself. Gasoline is a mixture of many different hydrocarbons, including oilfins, which are heavy, waxy compounds. The heavier the hydrocarbon, the more energy it yields when it burns. When the engine is shut off, the injectors undergo heat soak. Fuel residue in the injector nozzles evaporates, leaving the waxy oilfins behind. Because the engine is off, there is no cooling air flow through the ports and no fuel flow through the injectors to wash it away, so heat bakes the oilfins into hard varnish deposits. Over time, these deposits can build up and clog the injector .If a vehicle is used primarily for short-trip driving, the deposits may build up faster.



Dirty injectors lean out the fuel mixture and contribute to lean misfire, hesitation and even detonation. Cleaning should restore like-new performance.
How much additive does it take to provide an adequate level of protection? Industry sources say the recommended level is about 1,000 parts per million (ppm) of dispersant-detergent in the fuel which costs the gasoline supplier less than a penny a gallon. Even so, as much as 85% of the gasoline that is being sold contains only one-tenth of the recommended dosage, or only 100 ppm of additive. Consequently, using cheap gas contributes to the formation of injector deposits.

Cleaning injectors off-car takes more time and effort, but usually delivers much better results than on-car cleaning.

BENEFITS OF CLEANING FUEL INJECTORS
The benefits realized by injector cleaning obviously will vary depending on the condition of the injectors prior to cleaning and how badly they were clogged. Injectors that are really dirty should show more of a noticeable improvement in performance than ones that have only a light accumulation of deposits. Either way, performance, fuel economy and emissions should all be better after a cleaning. Most high-mileage engines as well as engines that are used mostly for short trip stop-and-go driving are the most likely prospects for injector cleaning. Some experts recommend cleaning the injectors every 25,000 to 30,000 miles to keep them flowing at peak efficiency.

Direct injection fuel injectors have very precise spray patterns and are even more sensitive to deposits than regular injectors. Observing the spray patterns of a set of injectors can show you at a glance if any are misshapen or contain streamers of unvaporized liquid.

Some experts recommend replacing the spark plugs after doing an on-car injection cleaning or decarbon treatment. The residue that is loosened and washed away by the solvent may increase the risk of plug fouling. Changing the oil and filters is also very important following a cylinder decarbon treatment because some of the solvent will get past the rings and end up in the crankcase.

FUEL INJECTOR CLEANING OPTIONS
Should you clean the injectors on the vehicle or remove them and use some type of injector cleaning machine? It depends.
The easiest route is to clean the injectors in place because you do not have to remove the injectors (which can be a real chore on some import engines). Running cleaner through the injectors while the engine is running also removes many of the deposits on the valves and inside the combustion chambers. This eliminates the need for an extra cleaning step if the engine is full of carbon deposits.

When doing the cleaning procedure itself, it is mandatory to use pressurized equipment to feed the solvent directly into the fuel rail while the engine is running. This means you either have to disable the fuel pump and plug the fuel return line, or install a U-tube so the fuel will re-circulate right back to the tank. Disabling the fuel pump can set a fault code on some cars, requiring you to clear the code after the job is done.

Easy as it is, there are some limitations with on-car injector cleaning. One is that badly clogged injectors may not pass enough solvent during a normal cleaning cycle to be thoroughly cleaned. Some baked-on deposits can be very difficult to remove, requiring you to prolong or repeat the cleaning process. And if on-car cleaning does not work? You will have to remove the injectors and have them cleaned on an injector cleaning machine - or replace them.
Another limitation with on-car injector cleaning is that you may have to do some additional tests to confirm that the injectors responded well enough to your cleaning efforts. A test drive may be needed to see if the driveability symptoms have been eliminated, or you may have to check emissions to make sure HC and CO levels are back to normal. A power balance test is another way to confirm engine performance and check for weak cylinders (there should be less than a 10% power variation between cylinders). An injector pressure drop test will tell you if the injectors are flowing evenly or not.

There may be some risk to the vehicle's fuel system when using concentrated solvent (fuel additives) to clean the injectors in place. Most equipment suppliers say to disconnect and plug the fuel return line so that solvent does not circulate back to the fuel tank. Strong solvents may attack rubber and plastic components in the fuel pump, regulator and fuel lines, creating additional problems that you don't need.

On-car injector cleaning also involves some risk to the person who's performing the service. You have to disconnect pressurized fuel lines, make sure there are no fuel leaks, and feed high-pressure solvent (which is just as flammable as gasoline) into the engine while the engine is running. Safety precautions should always include eye protection, making sure there are no open sources of ignition (sparks) nearby, and avoiding direct exposure with the cleaning solvent.

OFF-CAR FUEL INJECTOR CLEANING
Off-car injector cleaning is a more expensive service because of the labor involved to remove the injectors (which can be considerable on some applications), and it requires special equipment that can cost anywhere from $4,000 to $8,300.



Many shops charge between $30 and $35 per injector for off-car cleaning - which makes it more costly than on-car cleaning. But it also can motorists a lot of money because off-car cleaning is a lot cheaper than replacing the injectors with new ones (which can cost hundreds of dollars a set!).
Off-car injector cleaning can often restore dirty injectors that fail to respond to on-car cleaning. That is why some shops do only off-car cleaning. They do not want to have to clean the injectors twice. Off-car cleaning takes more time (typically 30 to 45 minutes after the injectors have been removed), and most machines have an ultrasonic bath that can be used to soak badly clogged injectors. Some machines also reverse-flush the injectors, which provides an added measure of cleaning.





Another reason for using off-car cleaning equipment is that the injectors can be flow-tested after they have been cleaned to verify their performance. The injectors typically are mounted on a test manifold and energized to spray solvent into clear graduated cylinders. By comparing the volume of fuel delivered, it is easy to see if all the injectors are flowing evenly.
As a rule, you should see less than 5% to 7% variation between injectors (some performance engine builders aim for 1% or less variation between injectors!). If an injector is not passing as much liquid as its companions, you can subject it to more cleaning. And, if it fails to respond to additional cleaning, there is no guesswork about which injector needs to be replaced.
Flow-testing also allows you to compare the actual flow rate of each injector to factory specifications. If the flow is within specifications, you know the injector should perform properly when it is reinstalled back in the engine. Flow-testing also is a good way to make sure the injectors are the right ones for the engine (one or more injectors may have been previously replaced by someone else).

A flow test on the cleaning equipment allows you to see each injector's spray pattern. If you see a normal, cone-shaped mist, you know the injector is flowing properly. If you see streamers of unvaporized liquid in the spray pattern, you know additional cleaning is needed or the injector needs to be replaced.