How to Adjust the Common Rail Injector Shims?

I believe that the common rail injectors and friends engaged in vehicle maintenance are no strangers to the concept of gaskets commonrailparts during normal use and repair. So what are the adjustable gaskets inside all kinds of common rail injectors? What are the functions and adjustment methods of common rail injector gaskets?

In fact, the replacement of parts is by no means a simple replacement. The corresponding assembly dimensions must be measured in detail, and the corresponding gasket thickness should be adjusted according to the results of the oil quantity test. Let’s take the Bosch fuel injector CRIN2 as an example to discuss in detail the effect of the adjustment gasket on the injection function.

First, the adjustment gasket of CRIN2 injector

First look at this structure diagram, in which the red box indicates five important gaskets, from top to bottom: valve spring adjustment gasket, armature lift adjustment gasket,injector adjusting shim B15 buffer lift adjustment gasket, grease nipple Spring adjustment washer and needle lift adjustment washer (intermediate sheet).

Valve spring adjustment gasket

Adjust the amount of spring force of the solenoid valve. Different types of injector valve spring force setting values ​​are different. The valve spring force setting of the CRIN injector ranges from 58N to 85N with a maximum allowable tolerance of ±3N. Too large and too small a valve spring force will affect the amount of fuel injected in the corresponding area.

Armature lift adjustment gasket

Adjust the maximum displacement of the ball valve up and down (ie, the armature lift). Different types of injectors have different armature lift settings. CRIN’s armature lift settings range from 40 microns to 60 microns, with CRIN2 injectors in the Chinese market mostly 52 microns or 55 microns with a maximum allowable tolerance of ±5 microns. If the armature lift is too large or too small,B11 it will directly cause the injector to not spray or the injection is seriously small. For CRIN injectors, within the normal deviation of the setpoint (±5 microns), the size of the armature lift will only affect the amount of pre-spray oil and will not affect other injection points.

Buffer lift adjustment gasket

Adjust the maximum displacement of the armature piece during the working process. The buffer lift gasket should not be too thick, otherwise it will directly cause the injector B12 to return a large amount of oil. Settings range from 20 microns to 60 microns with a maximum allowable tolerance of ±20 microns. As long as it is within the maximum allowable tolerance, its thickness and thickness will not affect the fuel injection amount of each single test point, and only affect the total amount of multiple injection fuel in a short time. The ordinary maintenance test bench is not available.

Oil nozzle spring adjusting gasket

Adjust the force of the oil spring force (commonly known as the nozzle needle opening pressure). The CRIN2 nozzle spring force is generally set to 34N with a maximum allowable tolerance of ±3N. Excessive spring force can cause deviations in fuel injection, especially in the idle phase.

Needle valve lift adjustment pad (middle piece)

Adjust the maximum displacement of the needle valve during operation. The setting varies with the type of injector,B13 typically ranging from 200 microns to 350 microns with a maximum allowable tolerance of ±10 microns. The size of the needle lift mainly affects the amount of fuel injected at the full load point.