ISO 12251:2017

ISO 12251 specifies dimensional requirements for clamp mounted CR fuel injectors and their corresponding cylinder head features in diesel engines.
According to the injector nozzle capnut, the clamp mounted CR fuel injectors can be divided into two types:
a) Type A, where the nozzle capnut is straight (see Figure 4);
b) Type B, where the nozzle capnut is stepped (see Figure 5).
Each clamp mounted CR fuel injector type is subdivided by a series of different sizes.
NOTE This differentiation corresponds to the relationship between the two guide diameters of the clamp mounted CR fuel injectors.