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High Performance Diesels
Cummins’ injector cleaner

Don’t lose this part number: 3885737. This is a diesel engine injector cleaner and can be purchased at any Cummins distributorship. The cleaner comes in a box that contains 1.25 gallons and must be used in its entirety.

To use this box of cleaner, the fuel suction line and return fuel line will have to be removed from the engine. Cummins has a hose kit part number 3885739, fleet price of $30.30, which is designed to be used with the injector cleaner. The directions are on the side of the box in English and Spanish.

The injector flushing should be performed outside because the engine will have to idle at 1,200 rpm for one hour. After the flushing or cleaning process is completed, the valves and injectors are now ready to be adjusted.

Why clean or flush injectors prior to setting the overhead? Carbon, which is a byproduct of diesel fuel that has been burned in a combustion chamber, will travel up through the small holes in an injector cup and form carbon deposits inside the cup and on the injector plunger. If the injector settings are loose, there will be a greater amount of carbon in the cup. Once the injector adjustments are properly set, the carbon is compacted into some of the holes in the injector cup. I’m sure that you have heard people say, “I had my rack run and now my truck runs worse.” Did you ever wonder why? Now you know what happened. Some of the holes are plugged with carbon. By the way, the injector flush should be used the evening before you plan to set the overhead because the engine will have to cool down to 70 F in order to properly set the overhead.

Carbon in injector cups can only be removed with an ultrasonic cleaner once the injectors are disassembled. When you send your injectors to be cleaned and calibrated, the carbon cannot be removed from the tips at that time. The Hartridge 290 injector test stand hammers very hard when carbon is present in the injector cup.

Please purchase the injector cleaner and hose kit from Cummins and flush the injectors prior to removing them for recalibration. It is a good practice to flush the injectors once a year, even if you are not going to reset the overhead. The cost of the cleaner is $37.87.

Do not use this injector cleaner in electronic engines. This caustic cleaner was designed only for mechanical engines. It was developed for use in STC (step timing control) engines, however, it works great in small cam through BC IV engines and STC N-14s.

Clean, properly adjusted injectors, diesel fuel fortified with Lucas fuel conditioner, and clean engine oil will enable the injectors to atomize the fuel to a fine mist state. The end result is better fuel mileage, greater performance and longer injector life.

My good friend Mike Robinson, the Caterpiller engine expert from Washington, DC, feels that the Cummins injector cleaner will do a fine job cleaning the 3406 C Cat nozzles. Carbon is carbon, and this stuff removes carbon.

Thanks to all Land Line readers who have been asking about my booklet. It is now available for viewing or download on the Internet. The address is Our e-mail address is as follows: Gary:; Pete:

If you would like our booklet on high performance Cummins diesels, give Aimee a call at (724) 274-4080. There is a $9 charge for shipping and handling. Just call us with your Master Card, Visa, AMX or Discover card number and we will get one out to you. Or send us a check or money order.

The above column is the opinion of the writer and does not necessarily reflect the opinion or beliefs of Land Line or Cummins Engine Co.