Foton & Dongfeng Cummins Armature Lift Adjustment Shim Set – A Kit 3.00-2.90 / B Kit 2.90-2.80 | 0.01mm Increment Precision Shims With Anti-Compression Coating

In Foton Cummins and Dongfeng Cummins common rail injectors (ISF, ISD, ISL, and ISG series), the armature lift-the distance the armature plate travels from its rest position to contact with the solenoid pole-is a fundamental parameter that directly influences injection timing and quantity. The armature lift is determined by the thickness of the adjustment shim, located between the armature plate and the retaining nut or valve stop. A variation of just 0.01 mm in shim thickness changes the armature lift by the same amount, altering the solenoid's magnetic pull-in characteristic and shifting the injection quantity by approximately 1.5–2.0 mm³/stroke. At 2,200 rpm, this translates to a 0.5° crank angle timing error, which can cause cylinder-to-cylinder imbalance and increase exhaust gas temperature by 10–15°C. The Foton & Dongfeng Cummins Armature Lift Adjustment Shim Set is a comprehensive shim kit, offered in two precision-graded ranges: Kit A (3.00 – 2.90 mm) and Kit B (2.90 – 2.80 mm) , with each kit containing ten thickness grades, five shims per grade, totalling 50 shims per kit.

The required shim thickness varies depending on the injector's wear condition and the specific injector model. New injectors typically use shims in the 2.85–2.95 mm range; worn injectors (where the armature plate and pole have experienced minor erosion) may require a thinner shim to restore the correct lift. The two kits cover the full service spectrum:

Kit	Thickness Range (mm)	Increment (mm)	Grades	Shims per Grade	Total Shims
Kit A	3.00 – 2.90	0.01	10	5	50
Kit B	2.90 – 2.80	0.01	10	5	50

The 0.01 mm increment allows fine adjustment of the armature lift to within ±0.005 mm-sufficient to achieve the target lift within the OEM tolerance band of ±0.02 mm.

Each shim is manufactured from hardened spring steel (equivalent to DIN 1.4034), heat-treated to HRC 45–48 to resist wear and compression. The shims have an internal diameter of 6.0 mm (matching the armature guide pin) and an external diameter of 12.0 mm. Both faces are precision-ground to a surface finish of Ra 0.4 µm, ensuring that the shim does not introduce any additional variation in the armature stack height.

Thickness Tolerance: ±0.005 mm (verified by laser micrometer)

Flatness: ≤ 0.005 mm (per DIN 8570)

Parallelism: ≤ 0.005 mm (between faces)

Surface Finish: Ra 0.4 µm (ground both faces)

Coating: Anti-compression nickel-phosphorus layer (5 µm), reducing surface deformation under the retaining nut load.

Each grade (thickness value) is supplied as a pack of five shims. This quantity is sufficient to adjust a full 6-cylinder engine (requiring six shims of potentially varying thicknesses, depending on the injector wear pattern) with one spare shim per grade. The five-shim pack also allows for "shim pairing"-using two thinner shims to achieve a thickness not available in a single grade, though this is not recommended for production-level adjustments.

Parameter	Kit A	Kit B
Thickness Range	3.00 – 2.90 mm	2.90 – 2.80 mm
Increment	0.01 mm	0.01 mm
Grades	10	10
Shims per Grade	5	5
Total Shims	50	50
Internal Diameter	6.0 mm	6.0 mm
External Diameter	12.0 mm	12.0 mm
Thickness Tolerance	±0.005 mm	±0.005 mm
Material	Hardened spring steel, HRC 45-48	Hardened spring steel, HRC 45-48
Surface Finish	Ra 0.4 µm (ground)	Ra 0.4 µm (ground)
Coating	Ni-P anti-compression, 5 µm	Ni-P anti-compression, 5 µm
Packaging	Individual poly-bags by grade, in a labeled case	Individual poly-bags by grade, in a labeled case

Q1: What is the difference between Kit A and Kit B, and why are they sold separately?
A: Kit A covers the higher thickness range (3.00–2.90 mm), which is typically used for new or lightly worn injectors. Kit B covers the lower range (2.90–2.80 mm), used for injectors that have experienced some wear and require a thinner shim to restore the lift. The two kits are sold separately so you can purchase only the range you need, rather than paying for both.

Q2: Can I use shims from Kit A and Kit B together in the same injector?
A: No. Each injector uses a single shim. You select one shim from the appropriate kit based on the measured required thickness. Mixing shims would create an uneven stack and is not permitted.

Q3: How many engines can I service with one kit?
A: Each kit contains 50 shims (10 grades x 5 shims). Assuming an average of 6 shims per engine (for a 6-cylinder engine, plus one spare), one kit can service approximately 8 engines, with some grades being used more frequently than others.

Q4: The shims are 6.0 mm internal diameter. Does that fit all injectors?
A: The 6.0 mm diameter is specific to Foton and Dongfeng Cummins injectors (ISF, ISD, ISL, ISG series). It also fits some Cummins XPI injectors. It does not fit Bosch or Denso injectors, which typically use a 5.5 mm or 6.5 mm guide pin.

Q5: How do I know which grade to use?
A: You determine the required thickness by measuring the installed height and calculating the shim thickness using the formula provided in the injector service manual. The kit includes a quick-reference card with the formula and target lift values for each engine family.

Q6: Can I reuse an old shim?
A: We strongly recommend against reusing shims. The nickel-phosphorus coating may have been compressed or damaged during the previous installation, and the shim may have work-hardened, leading to inconsistent thickness or flatness. Always use a new shim.

 

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