14869   Yellow   Water  Lane
                                                                        Jacksonville,  Florida   32234


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                                    CIS gas petrol injector cleaning, testing, and service.
                                 K-Jetronic gas petrol injector cleaning, testing, service.
                                       Mechanical injector cleaning, testing, and service.


Testing and ultrasonic cleaning for Mercedes CIS injectors, Porsche CIS injectors, Ferrari CIS injectors, Volvo CIS injectors, Audi CIS injectors, VW CIS  injectors.


CIS is an acronym for continuous injection system.  It is also commonly referred to as the Bosch   K- Jetronic injection system.  The injectors may also be referred to as mechanical injectors, as they have no electrical connection.  The principle operation of the CIS system is as follows.  CIS injectors are mechanical injectors.  They are not operated by an electrical voltage on an internal injector coil, as is found on an MPI injection system.  Rather, a CIS system and injector, operates via variable fuel pressure as delivered via the engines' fuel distribution head.  When a CIS vehicle ignition switch is turned to the "start" position, the fuel pump is energized, fuel pressure increases in the fuel distribution head, and the injectors are opened via the increased fuel pressure...(by way of  internal injector spring tension)...and injector fuel delivery volume is then controlled by the fuel pressure that varies within the fuel distribution head...based upon engine demand.


The CIS injection system was commonly used on Mercedes, Volvos, VW's, Audi's, Porsche, and other vehicles from 1973 thru 1995.  As the CIS injection system is no longer used on the newer vehicles, it is difficult to obtain servicing on the system, locating replacement parts, locating replacement injectors, and locating flow testing and ultrasonic cleaning service sources for CIS injectors.


As such, we find it necessary to provide a location for testing and servicing of your CIS injectors.  It not only may eliminate the cost of acquiring new CIS injectors...but it also allows your injectors to be ultrasonically cleaned and serviced, and tested for "crack open" pintle pressure and  fuel delivery flow, such that your vehicle performs at its' maximum potential.  Testing and ultrasonic cleaning of CIS injectors is about 60% to 75% less than purchasing new replacement CIS injectors, depending on the engine and the specific injector ritted.


We can service CIS injectors, and in many cases, restore flow rates to OEM specs.  We have the ability to service the following CIS injectors...which is, just about all of them.....


1)  CIS injectors with a 12 mm OD male thread.

2)  CIS injectors with a 10 mm OD male thread.

3)  CIS injectors with a   8 mm  ID  male thread.  (which should include cold start injectors).

4)  CIS injectors with a   8 mm  ID  female thread.


CIS injectors must be tested individually.  They cannot be tested as a group, as in the MPI (multi port injection) series injectors.  The reason is...the "crack" or open pressure of the injector pintle, may vary per injector.  The "crack open" pressure is the pressure at which the injector pintle lifts off the pintle seat and the injector begins flowing fuel.   If CIS injectors are batch tested, and if one injector opens prior to others in the set,  then  the "crack open" pressure of the remaining injectors is "skewed" by the first injector that opens, and fuel flow delivery rates will not be accurately tested.


With the above in mind, it is important  that all CIS injectors open within a correct  "fuel pressure window", and equally important...that once opened...they provide a flow rate within at least a 10% flow deviation.


When your CIS injectors are received...they are scribed on the side with a number, which allows each injector to be "tracked" in the flow testing and cleaning process.  Each individual injector is then checked for its' individual "crack open" pressure, spray pattern, and then flow tested for fuel volume delivery.  Flow testing is typically conducted at appx 0.5 Bar or 1 Bar pressure above the "crack open" pressure.  Those results are logged.


There are two separate ultrasonic cleaning processes that we conduct on CIS injectors.  The first ultrasonic cleaning process, cleans the tip end of the injectors.  The tip end (which is the orifice [pintle] opening end of the injector), is submerged in the ultrasonic cleaner, such that only the discharge tip of the injectors is cleaned, (removing burned on fuel olafins from the injector tip).  Upon completion of this step, the second ultrasonic cleaning process lays the injectors horizontally within the ultrasonic cleaner (such that the injectors are completely submerged within the cleaning tank), to loosen/remove internal "sludge" from within the injectors, and to remove external "sludge" buildup on each injector.


The injectors are then individually retested for the "crack open" pressure, spray pattern,  and flow rate, and results are logged.


If the two step cleaning process as above does not correct "crack open" pressure and flow rates, we will add a third step.....fill the injector(s) with a solvent and allow the injector(s) to soak, and the solvent to dissolve any internal gunk.  The solvent is then blown out with compressed air, and the injector(s) tested again.  In our experience, this is usually required, and in severe cases, may have to be performed several times over during a period of 2-3 days.  An additional cost will be incurred to perform this service, and is dependent on time required.  


Cost of service is as follows for the two step cleaning process as detailed above ....


Per injector..............$22.00.


If step three is required, the additional cost is approximately $4.00-$5.00/per injector.


We do not stock o-rings or other replacement parts for CIS injectors.  You will need to obtain these items from your dealer, or alternate source.


CIS injector testing includes a full written report of pre and post cleaning results. Alternately, results may be sent via e-mail, in which case, you should print or save the e-mail.  E-mailing provides quicker results, and is the preferred method to get you a result.

I need to know the following information on your vehicle.  The make, the model, engine size (cc or cubic inches), number of cylinders, whether turbo charged, supercharged, or normally aspirated, and the rated HP.   


Return shipping to any continental USA location is $12.95...via USPS Priority Mail, plus $5.00 to insure your shipment.



As with any injector, rust within the injector is extremely difficult (if not impossible) to remove.  Most injectors that contain internal rust...require replacement.  However, in some instances, the ultrasonic cleaning process may remove very light rust.  

Currently, we do not stock replacement CIS injectors, but we can order them for you.

CIS injectors are no where near as reliable as electrically operated injectors.  We find that even new CIS injectors (right off the shelf) have a 30 to 40 % failure from improper flow rates, and we highly recommend...if you need replacement injectors..... having any new CIS injector(s)  flow tested. This is based upon our 10 years of experience of flow testing CIS injectors.  

CIS injectors may fail due to a weak internal spring.  We cannot replace the spring.  If the spring is weak, the injector requires replacement.  A weak spring will cause that particular injector to open early, and overfuel, or leak, and result in an unbalanced fuel flow of the injector group.


FYI...Many auto forums inquire if CIS injectors can be back flushed.  The simple answer is NO.  Back flushing occurs on electrically operated injectors when the injectors are placed in the ultrasonic cleaner, the injectors are electrically pulsed on/off, and the cleaning solution backflows out the top end of the injector, which flushes any internal gunk out the injector from the top end.  Because CIS injectors cannot be pulsed on/off, there can be no back flushing.  When we clean CIS injectors, compressed air is used to force any internal gunk out the pintle end of the injector.  



If you have a question on your CIS injectors, feel free to send me an E-MAIL.  Be sure to indicate your vehicle year, exact model, exact engine size, number of engine cylinders, and injector number (if you have it).  


               We also service a multitude of electrically operated MPI injectors, too many to list here.   For
                               additional information...please
CLICK HERE  to go to my web site home page.

For immediate assistance, call our shop at 904-289-2020. Eastern standard time.  We are located in Jacksonville, Florida.  If you get our voice mail recording, leave a message and we will return your call ASAP. 


                                                        This page last updated on March 10, 2014.