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Common Rail Injector Adjusting Shims
When comes to common rail injectors and its maintenance,you must be familiar to adjusting shims which act an important role in the entire working process.So do you know how many adjusting shims inside and their function?Today we will take BOSCH CRIN2 injectors as example and make make a brief introduction.
Adjusting shims in CRIN2 injectors
common rail injectors adjusting shims
1.1 Valve Spring Shim
Adjust the spring force of solenoid valve.For the different common rail injector valve spring force,they are set to be different.It's set from 58N to 85N for bosch CRIN injector with the maximum allowable tolerance of + / - 3N. The corresponding area of the injection amount will be affected no matter valve spring force too large or too small.
1.2 Armature lift adjusting shims
We call adjusting the maximum displacement of ball valve jumping up and down as armature lift.The setting value of different injectors armature lift are also different.The armature lift value of CRIN varies from 40 micron to 60 micron, among which the CRIN2 generation injectors in the Chinese market are mostly 52 micron or 55 micron, with the maximum allowable tolerance of plus or minus 5 micron.Too large or small armature lift will directly result in that the injector does not spray oil or injection seriously too small.For the CRIN injector, the armature lift only affects the oil amount at the pre-injection point within the normal deviation of the set value (plus or minus 5 microns and does not affect other injection points.
1.3 Nozzle adjusting Shims
Adjust the spring force of nozzle (commonly known as the opening pressure of nozzle needle valve).CRIN2 nozzle spring force is generally set at 34N, with the maximum allowable tolerance of + or - 3N.If the spring force is not good enough,it will result in deviation of injection amount, especially in idle stage.
1.4 Buffer lift adjusting shim
It adjusts the maximum displacement of armature sheet during operation.Too thick buffer lift adjusting shim is not allowed,otherwise it will directly lead to a large amount of fuel return from the injector.It sets values range from 20 microns to 60 microns with a maximum allowable tolerance of plus or minus 20 microns.As long as it is within the maximum allowable tolerance, its thickness and thinness will not affect the amount of oil injected at each single test point, but only the total amount of oil injected multiple times in a short time.It can't be measured out by common maintenance test bench.
1.5 Needle valve lift adjusting shims (intermediate plate)
It adjusts the maximum displacement of armature sheet during operation.The setting values vary with injector numbers, generally ranging from 200 micron to 350 micron, with a maximum allowable tolerance of plus or minus 10 micron.The needle valve lift mainly affects the amount of fuel injection at the full load point.

In short,when you need to replace any components during maintenance,you need to measure the corresponding assembly size in details and the corresponding gasket / shims thickness must be adjusted according to the oil test results.