Tech Tip #162: Cummins B Series Injector Protrusion

Dr. Diesel
Written by Dr. Diesel


 This Tech Tip is one of a series we publish for the engine community.  It focuses on setting the protrusion of fuel injector tips for Cummins B Series engines. For earlier Dr. Diesel™ Tech Tips on the Cummins B Series engine see Tech Tip #55: Cummins B Series Tachometers and Tech Tip #109: Cummins B Series Reman Exchange Engines.

 The Cummins B Series engine is a popular engine. It has been widely used in automotive, industrial and marine applications. Cummins B Series as used in automotive applications are found in Dodge trucks as well as some specialized chassis. Cummins B Series as used in industrial applications are found in many wood chippers, Hyster rollers and fork lifts, etc. Most mechanics that work on the Cummins B Series have experience working on the Cummins B Series in Dodge pickups and generalize from that. This can lead to problems.

When installing new or remanufactured Cummins B Series fuel injectors, some people assume that the injector protrusion spec is the same for all applications and just set them for the same spec as used in automotive B Series. This is a common error and can lead to problems because the protrusion is different for the Cummins B series industrial engine.
To help you set the fuel injector protrusion on the Cummins industrial B Series, please take a look below.
Injector Protrusion for the Cummins B Series Industrial Engine
(Note: automotive and marine are different)
Min Protrusion
Max Protrusion
If you need to adjust the protrusion on your B Series we have injector seals in different dimensions.  However, there is a slight difference between the nominal size of the seal and its actual thickness.
The chart below lists the actual seal thickness for three different B Series Injector Seals.
Seal (nominal)
MM (actual)
Inch (actual)
1.5 MM
1.40 – 1.68
.055” – .066”
2.5 MM
2.40 – 2.68
.095” – 1.06”
3.0 MM
2.90 – 3.16
1.14” – 1.25”
We hope that this Tech Tip has been helpful. Foley Engines stocks over 20,000 square feet of engine parts kits for Cummins B Series engines.  Please call us at 800.233.6539 or email Dr. Diesel™ at with any questions to order an engine kit or a Workshop Manual.


Dr. Diesel
Written by Dr. Diesel
Knowledge is power. Power to build ties to engine users. To build a relationship with our customers, we share with you our 105 years of knowledge in many ways. We have this special section called “Ask Dr. Diesel™” where you can pose questions about engines, transmissions, industrial hand clutches, exhaust scrubbers, etc.