Inside Injector Adjustment Shim: Standards, Structure, and How It Supports Industrial Applications

Types of Injector Adjustment Shims

An injector adjustment shim is a precision-engineered component used to fine-tune the performance of fuel injectors by adjusting the preload or clearance within the injector assembly. These shims play a critical role in ensuring optimal fuel delivery, combustion efficiency, and engine longevity. Available in various materials and designs, each type of shim is tailored for specific operational demands, environments, and performance goals.

Shim C

Made from solid cobalt-chrome alloy, Shim C is engineered for extreme environments requiring superior resistance to heat, corrosion, and mechanical stress.

Advantages

• Exceptional high-temperature stability
• Outstanding corrosion resistance
• Durable under heavy thermal cycling
• Reliable in high-load applications

Limitations

• Higher manufacturing cost
• Heavier than aluminum alternatives
• Limited availability outside specialized sectors

Best for: Aerospace, military systems, offshore oil & gas equipment

Shim W

Precision-crafted with smooth surfaces and refined edges, typically made from stainless steel or aluminum for clean, fatigue-resistant performance.

Advantages

• High dimensional accuracy
• Excellent fatigue resistance
• Easy to clean and sterilize
• Ideal for sensitive environments

Limitations

• Less suited for high-temperature applications
• May require protective coatings in corrosive settings
• Not ideal for high-vibration machinery

Best for: Medical devices, laboratory equipment, cleanroom manufacturing

S-Type Shim

Features a tapered design made from hardened steel alloy, optimized for reducing friction and enhancing fluid dynamics in high-stress environments.

Advantages

• Superior tensile strength
• Reduces fluid flow resistance
• Minimizes wear between nozzle and shim
• Excellent for dynamic loading conditions

Limitations

• More complex to manufacture
• Requires precise alignment during installation
• Higher cost due to specialized shaping

Best for: Heavy-duty vehicles, industrial engines, mining and construction machinery

Parker Shim

Utilizes a patented design with heat-treated stainless steel, ensuring consistent performance in diesel fuel injector systems under extreme thermal conditions.

Advantages

• Enhanced thermal stability
• Improves fuel atomization and efficiency
• Long service life with minimal degradation
• Widely standardized in automotive OEMs

Limitations

• Proprietary design may limit sourcing options
• Potential compatibility issues with non-OEM parts
• Premium pricing compared to generic shims

Best for: Diesel engines, automotive manufacturing, commercial transport fleets

B-Type Shim

Constructed from brass or bronze with a standard cylindrical shape, offering excellent corrosion resistance in marine and humid environments.

Advantages

• Natural resistance to saltwater corrosion
• Good thermal conductivity
• Reduces injector wear over time
• Cost-effective for marine applications

Limitations

• Lower strength compared to steel alloys
• Not suitable for high-pressure fuel systems
• May deform under extreme loads

Best for: Marine engines, boats, offshore vessels, coastal infrastructure

Shim Type	Material	Durability	Environment	Key Application
Shim C	Cobalt-Chrome Alloy	Excellent	Extreme heat, high load, corrosive	Aerospace, military, offshore
Shim W	Stainless Steel / Aluminum	Very Good	Clean, precision-critical	Medical devices, lab equipment
S-Type	Hardened Steel Alloy	Excellent	High stress, dynamic loads	Industrial machinery, heavy vehicles
Parker Shim	Heat-Treated Stainless Steel	Excellent	High temperature, diesel systems	Automotive, diesel engines
B-Type	Brass / Bronze	Good	Marine, saltwater exposure	Boat engines, ships

Expert Tip: Always verify shim specifications—including thickness, material grade, and tolerance—before installation. Using incorrect shims can lead to improper injector seating, fuel leakage, or reduced engine performance. When in doubt, consult OEM service manuals or technical datasheets.

Specifications and Function of Injector Adjustment Shim

Injector adjustment shims are precision-engineered components critical to the accurate operation of fuel injection systems in internal combustion engines. These small yet vital parts ensure optimal injector performance by fine-tuning the position and pressure of the injector nozzle. Proper selection and installation of shims directly influence fuel delivery accuracy, engine efficiency, emissions compliance, and component longevity.

Technical Specifications

Material Composition

Injector adjustment shims are fabricated from high-performance materials tailored to specific operational demands:

• Stainless Steel: Offers excellent corrosion resistance, ideal for marine and high-humidity environments.
• Hardened Steel: Provides superior wear resistance and structural integrity under repeated mechanical stress.
• Ceramic: Used in extreme-temperature applications due to its thermal stability and low thermal expansion.
• Copper Alloys: Chosen for high thermal conductivity, helping dissipate heat from injector components.

Material choice significantly affects durability, performance, and compatibility with fuel types and operating conditions.

Dimensional Accuracy

Precision is paramount in shim manufacturing. Tolerances typically range from 0.01 mm to 0.001 mm, ensuring exact positioning of the injector plunger or nozzle. Even minor deviations can result in:

• Inaccurate fuel metering
• Increased fuel leakage
• Erratic injection timing
• Poor combustion efficiency

Advanced machining techniques such as CNC grinding and laser measurement are used to maintain these tight tolerances during production.

Thickness Variation

Shims are available in a range of thicknesses—typically from 0.1 mm to 2.0 mm—to allow precise calibration of injector lift and opening pressure. The thickness directly influences:

• Nozzle Opening Time: Thinner shims reduce clearance, enabling faster nozzle response and earlier fuel delivery.
• Injection Duration: Thicker shims increase gap, delaying opening and shortening effective injection time.
• Atomization Quality: Optimal thickness ensures proper spray pattern formation for efficient combustion.

Technicians use calibrated shim kits to fine-tune injectors during engine tuning or overhaul procedures.

Heat Resistance & Thermal Stability

Fuel injectors operate in high-temperature zones, often exceeding 200°C. Injector shims must maintain dimensional stability under these conditions. Materials like ceramic and hardened steel exhibit minimal thermal expansion, preventing:

• Deformation under heat
• Loss of preload on injector components
• Drift in injection timing

Thermal resilience ensures consistent performance across cold starts, sustained operation, and rapid temperature cycles.

Tensile Strength

To withstand mechanical loads from fuel pressure (often exceeding 200 bar) and injector actuation forces, shims require high tensile strength—typically over 600 MPa. This strength prevents:

• Plastic deformation
• Cracking or fracturing
• Settlement or compression over time

High-strength materials ensure long-term reliability and consistent injector adjustment without drift.

Corrosion Resistance

Exposure to fuel additives, moisture, and combustion byproducts necessitates corrosion-resistant materials. Common solutions include:

• Brass and Copper Alloys: Naturally resistant to oxidation and chemical degradation.
• Coated Steels: Nickel or zinc plating enhances durability in aggressive environments.
• Stainless Steel Grades (e.g., 304, 316): Ideal for marine and biofuel applications.

Corrosion protection maintains surface finish and dimensional accuracy, preserving injector function over extended service intervals.

Technical Parameter	Typical Range/Value	Functional Impact
Material Types	Stainless steel, hardened steel, ceramic, copper alloys	Determines durability, thermal response, and environmental compatibility
Thickness Range	0.1 mm – 2.0 mm	Controls injector opening time and fuel delivery precision
Dimensional Tolerance	±0.001 mm to ±0.01 mm	Ensures accurate injector seating and consistent performance
Operating Temperature	Up to 250°C (material-dependent)	Maintains integrity under extreme engine heat
Tensile Strength	≥ 600 MPa	Resists deformation under mechanical and hydraulic loads
Corrosion Resistance	High (material/coating dependent)	Prevents degradation in humid, marine, or chemically aggressive environments

Functionality Features

Fuel Efficiency Enhancement: By precisely adjusting the injector's operational gap, shims regulate fuel metering accuracy. This ensures optimal air-fuel ratios across all engine loads, improving combustion efficiency and reducing fuel consumption. Properly shimmed injectors contribute directly to lower operating costs and improved mileage.

Engine Performance Maintenance: Shims enable fine-tuning of injection timing and spray characteristics, allowing the engine to deliver consistent power output under varying conditions—from idle to full throttle. This results in smoother acceleration, reduced hesitation, and enhanced drivability.

Durability Extension: Correctly sized shims distribute mechanical stress evenly across injector components, minimizing localized wear on plungers, nozzles, and seats. This balanced loading reduces fatigue and extends the service life of both the injector and surrounding engine parts, decreasing maintenance frequency and downtime.

Emissions Control: Precise fuel delivery enabled by accurate shim adjustment promotes complete combustion, significantly reducing harmful emissions such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). This helps engines comply with stringent environmental standards like Euro 6 and EPA Tier 4.

Improved Injector Nozzle Sealing: Shims help establish the correct preload on injector components, ensuring a tight seal between the nozzle and body. This prevents fuel leakage, stabilizes rail pressure, and eliminates erratic spray patterns, resulting in reliable performance and reduced emissions.

Important: Always use OEM-specified or certified replacement shims during injector servicing. Using incorrect thickness or substandard materials can lead to improper injection timing, increased emissions, engine knocking, or catastrophic injector failure. Follow manufacturer guidelines for measurement, selection, and installation procedures to ensure peak engine performance and safety.

Scenarios for Injector Adjustment Shim Applications

Injector adjustment shims play a crucial role in precision fuel delivery systems across multiple high-performance and demanding industries. These small yet vital components fine-tune the position and operation of fuel injectors, ensuring optimal spray timing, duration, and atomization. By adjusting the preload or lift of the injector nozzle, shims directly influence combustion efficiency, engine performance, emissions output, and component longevity. Below are key application scenarios where injector shims are essential for reliable and efficient operation.

Diesel Engine Maintenance

Diesel engines rely on high-pressure fuel injection systems to deliver fuel directly into the combustion chamber with extreme precision. The injector adjustment shim controls the injector's seating depth and operational clearance, which directly affects nozzle opening pressure and injection timing. Even minor deviations can lead to incomplete combustion, reduced fuel economy, increased emissions, and excessive soot buildup.

• Shims ensure consistent injector performance across varying engine loads and temperatures
• Precise shim thickness maintains optimal valve lash and injector actuation timing
• Custom-machined shims compensate for wear in aging engines, restoring factory specifications
• Used during injector rebuilds or replacements to match OEM tolerances

Key Benefit: Improved fuel efficiency, lower emissions, and extended injector life through accurate calibration.

Aerospace Applications

In aerospace propulsion systems—particularly in gas turbine and rocket engines—fuel injector precision is paramount. Injector shims are used to calibrate fuel nozzles that operate under extreme temperatures, pressures, and altitudes. These components must maintain exacting tolerances to ensure stable combustion, prevent flameout, and maximize thrust-to-weight ratios.

• Manufactured from high-strength, heat-resistant alloys like Inconel or titanium
• Engineered to withstand thermal cycling and vibration in flight environments
• Enable fine-tuning of fuel-air mixture for optimal combustion stability
• Critical in afterburner and main burner nozzle assemblies

Critical Requirement: Zero failure tolerance—shims undergo rigorous QA testing and traceability protocols.

Heavy-Duty Machinery

Construction, mining, and agricultural equipment operate under harsh conditions with high dust, vibration, and load cycles. Fuel injector shims in these applications are designed to maintain consistent fuel delivery despite extreme mechanical stress and contamination risks.

• Made from hardened steel or nitrided alloys to resist deformation and wear
• Ensure stable injection timing in large-bore diesel engines used in excavators, haul trucks, and tractors
• Reduce injector tip coking and carbon buildup by maintaining proper seating
• Extend service intervals and reduce unplanned downtime

Operational Impact: Enhanced engine reliability and reduced maintenance costs in rugged environments.

Marine Settings

Marine diesel engines, especially those used in commercial shipping, offshore platforms, and naval vessels, face constant exposure to saltwater, humidity, and long operational cycles. Injector adjustment shims in these systems must resist corrosion while maintaining dimensional stability over time.

• Constructed from marine-grade stainless steel or coated alloys (e.g., nickel-plated)
• Prevent galvanic corrosion when in contact with aluminum or cast iron components
• Ensure consistent fuel metering during prolonged voyages and variable sea conditions
• Marine grade injector adjustment shims are certified to meet ISO 8099 and other maritime standards

Long-Term Value: Corrosion-resistant shims protect engine integrity and support global logistics and defense operations.

High-Performance Automotive

In sports cars, supercars, and tuned performance vehicles, injector precision directly impacts throttle response, horsepower output, and engine smoothness. Injector adjustment shims allow tuners and manufacturers to fine-tune fuel delivery for peak performance across the RPM range.

• Used in direct-injection and turbocharged engines requiring exact fuel timing
• Made from precision-ground materials to tolerances within ±0.001 mm
• Support engine calibration during ECU remapping or forced induction upgrades
• Minimize fuel leakage and ensure rapid nozzle closure for cleaner combustion

Performance Edge: Enables optimal air-fuel ratios under high-load conditions for maximum power and drivability.

Additional Industry Uses

Beyond the primary applications, injector shims are also found in specialized sectors where fuel control is critical:

• Racing Engines: Custom shim packs used for track-specific tuning and rapid engine rebuilds
• Power Generation: Backup diesel generators use shims to maintain injector reliability during emergency operation
• Off-Road Vehicles: Desert and rally vehicles benefit from durable shims that handle thermal extremes
• Aftermarket Tuning: Performance shops use shims to calibrate upgraded injectors for modified engines

Universal Principle: Any application requiring precise fuel metering benefits from properly adjusted injectors via shims.

Expert Insight: Always verify shim specifications against OEM service manuals or technical bulletins before installation. Using incorrect shim thickness can lead to poor combustion, increased emissions, injector damage, or even piston contact in extreme cases. When rebuilding injectors, measure wear on mating surfaces and consider using laser-etched, traceable shims for critical applications.

Application	Common Materials	Typical Tolerance	Key Performance Goal
Diesel Engines	Tempered Steel, Stainless Steel	±0.01 mm	Fuel Efficiency & Emissions Control
Aerospace	Inconel, Titanium, Nickel Alloys	±0.002 mm	Combustion Stability at High Altitude
Heavy-Duty Machinery	Hardened Steel, Nitrided Alloys	±0.01 mm	Durability Under Vibration & Load
Marine	Marine-Grade Stainless, Coated Steel	±0.01 mm	Corrosion Resistance & Longevity
High-Performance Automotive	Precision-Ground Alloy Steel	±0.005 mm	Peak Power & Throttle Response

Best Practices for Injector Shim Selection

• Match OEM Specifications: Use manufacturer-recommended thickness and material for replacement
• Measure Before Replacing: Check injector pocket depth and wear before selecting new shims
• Use Calibrated Tools: Micrometers and surface plates ensure accurate thickness verification
• Document Changes: Record shim thickness during service for future diagnostics
• Source from Reputable Suppliers: Choose ISO-certified manufacturers with traceable quality control

How to Choose the Right Fuel Injector Adjustment Shim

Selecting the correct fuel injector adjustment shim is a precision task that directly impacts engine performance, fuel efficiency, and long-term reliability. These small yet critical components fine-tune the position of the fuel injector within the engine, ensuring optimal spray pattern, timing, and fuel delivery. This comprehensive guide outlines the key factors to consider when choosing an injector shim, from material selection to engine-specific requirements, helping both DIY enthusiasts and professional mechanics make informed decisions.

Important Note: Incorrect shim selection can lead to poor combustion, increased emissions, reduced fuel economy, and potential engine damage. Always verify specifications before installation and follow manufacturer guidelines precisely.

Material Composition: Matching Durability to Engine Demands

The material of the adjustment shim must withstand extreme operating conditions, including high temperatures, pressure fluctuations, and exposure to fuel and combustion byproducts. Choosing the right material ensures longevity and consistent performance.

• Stainless Steel Shims: Ideal for diesel engines and fuel systems prone to moisture or corrosive environments. Stainless steel resists oxidation and maintains dimensional stability over time, making it perfect for marine applications or vehicles operating in humid climates.
• Hardened Steel Shims: Recommended for high-performance, turbocharged, or heavy-duty engines where mechanical stress is significant. These shims are heat-treated to increase hardness and resistance to compression, preventing deformation under high injector loads.
• Coated or Nitrided Variants: Some OEMs use surface-treated shims to enhance wear resistance and reduce friction between mating surfaces, especially in direct-injection systems.

Always ensure the shim material is chemically compatible with your fuel type (diesel, gasoline, biodiesel, etc.) to avoid degradation.

Thickness and Size: Precision Tuning for Optimal Fuel Delivery

The thickness of the adjustment shim directly affects the seated position of the fuel injector, which in turn influences the nozzle opening pressure and spray geometry. Even a variance of 0.01 mm can alter engine performance.

• Thicker Shims: Raise the injector slightly, increasing the preload on the injector valve. This typically results in higher fuel injection volume and earlier opening, beneficial for engines requiring more fuel delivery due to wear or performance upgrades.
• Thinner Shims: Lower the injector position, reducing preload and delaying or decreasing fuel delivery. These are often used in well-maintained engines for fine-tuning idle quality and low-end response.
• Size Compatibility: Ensure the outer diameter (OD), inner diameter (ID), and profile (flat, stepped, or beveled) match the injector body and cylinder head seat exactly. Mismatched dimensions can cause misalignment, leaks, or improper seating.

Use precision micrometers to measure existing shims during disassembly and refer to service manuals for allowable tolerance ranges.

Shim Thickness Range	Typical Application	Effect on Injection	Common Engine Types
1.00 – 1.49 mm	Fine-tuning, newer engines	Slight reduction in fuel volume	Modern gasoline, small diesel
1.50 – 1.99 mm	Standard adjustment range	Balanced fuel delivery	Most OEM applications
2.00 – 2.50 mm	Worn engines, high-output tuning	Increased fuel volume and pressure	Turbo diesel, performance builds

Professional Consultation: When Expertise Matters

Fuel injection systems vary significantly between manufacturers and models, and incorrect shim selection can lead to serious drivability issues or engine damage. If you're unsure about specifications or lack diagnostic tools, professional guidance is essential.

• Contact a certified diesel technician or fuel system specialist who has access to factory service data and calibration tools.
• Consult the vehicle manufacturer’s technical service bulletins (TSBs) for known issues related to injector shim wear or recalibration.
• Use diagnostic software to monitor injection timing, rail pressure, and combustion efficiency before and after shim changes.

Guessing the correct shim size based on symptoms alone can lead to misdiagnosis. A professional can perform injector pop tests and flow bench analysis to determine exact requirements.

Engine Condition: Tailoring Shim Choice to Wear and Performance

The current mechanical state of the engine plays a crucial role in determining the appropriate shim thickness.

• Well-Maintained Engines: Use thinner or standard-specification shims to maintain factory-calibrated injection parameters. These engines benefit from precise, minimal adjustments to preserve efficiency and emissions compliance.
• High-Mileage or Worn Engines: As components like injector seats, cylinder heads, or plungers wear down, they can alter injector seating depth. Thicker shims help compensate for this wear, restoring proper nozzle control and combustion efficiency.
• Rebuilt or Modified Engines: After an overhaul or performance upgrade, always recalibrate injector shims based on new component dimensions and desired fuel maps.

Regular inspection of removed shims for pitting, warping, or scoring can provide insights into overall engine health.

Usage of OEM Shims: Ensuring Quality and Compatibility

Original Equipment Manufacturer (OEM) shims are engineered to exact tolerances and tested under real-world conditions, offering unmatched reliability compared to generic aftermarket alternatives.

• OEM shims are manufactured with strict quality control, ensuring consistent thickness, flatness, and material integrity across batches.
• They are specifically designed to match the injector’s spring load, nozzle design, and combustion chamber geometry for each engine model.
• Aftermarket shims may vary in quality, leading to inconsistent performance, premature failure, or voided warranties.

While OEM shims may cost more initially, their precision and durability reduce the risk of repeat repairs and ensure long-term engine protection.

Expert Tip: Keep a log of all shim measurements and changes made during injector servicing. This record helps track wear trends, simplifies future maintenance, and aids in diagnosing recurring performance issues.

Additional Best Practices

• Always clean injector bores and mating surfaces thoroughly before installing new shims.
• Replace shims as a set when servicing multiple injectors to ensure uniform performance across cylinders.
• Use calibrated torque settings when reinstalling injector hold-down bolts to prevent distortion.
• After replacement, bleed the fuel system and perform a smoke test or pressure check to confirm integrity.
• Monitor engine performance during the first 50–100 miles post-installation to detect any irregularities early.

Proper injector shim selection is not just about fitting a part—it's about maintaining the delicate balance of fuel delivery that modern engines demand. By prioritizing material quality, precise sizing, OEM components, and expert advice, you ensure your engine runs smoothly, efficiently, and reliably for thousands of miles.

Frequently Asked Questions About Fuel Injector Adjustment Shims

Q1: How Does a Fuel Injector Adjustment Shim Work?

A fuel injector adjustment shim is a precision-engineered component designed to fine-tune the position of the fuel injector nozzle within the injector body. By inserting a thin shim between the nozzle and the injector housing, technicians can precisely control the distance the nozzle extends into the combustion chamber.

This adjustment directly influences the fuel spray pattern, atomization quality, and injection timing—critical factors for efficient combustion. Shims are manufactured in a range of thicknesses (often measured in microns or thousandths of an inch), allowing for micro-adjustments to achieve optimal injector performance.

Properly adjusted shims ensure that fuel is delivered in a finely atomized mist, which burns more completely, resulting in:

• Improved engine power and responsiveness
• Enhanced fuel efficiency
• Reduced emissions (especially hydrocarbons and particulates)
• Smaller risk of carbon buildup and injector clogging

This level of precision is particularly vital in high-performance, diesel, and modern direct-injection engines where even minor deviations can significantly impact engine behavior.

Q2: What Is the Composition of a Fuel Injector Adjustment Shim?

Fuel injector adjustment shims are constructed from high-grade, durable materials capable of withstanding extreme operating conditions—including high pressure, temperature fluctuations, and exposure to corrosive fuels. The choice of material depends on the engine type, fuel system design, and environmental demands.

Common materials used include:

• Hardened Steel: Offers exceptional strength and wear resistance, ideal for high-stress diesel engines where injector pressures can exceed 30,000 psi.
• Stainless Steel: Provides excellent corrosion resistance, making it suitable for environments with high moisture content or alternative fuels (e.g., biodiesel, ethanol blends).
• Brass: Used in some applications for its machinability and moderate durability, though less common in modern high-pressure systems.
• Ceramic or Coated Alloys: Found in advanced or performance applications where thermal stability and resistance to micro-welding are critical.

Regardless of material, all shims must maintain dimensional stability over time. Even slight warping or erosion can alter the injector’s spray geometry, leading to performance issues. Precision manufacturing ensures tolerances within ±1–2 microns, guaranteeing consistent performance across the engine’s lifespan.

Q3: When Should Fuel Injector Adjustment Shims Be Replaced?

While fuel injector shims are built to last, they are not immune to wear and degradation. Replacement is typically recommended under the following circumstances:

• During Injector Overhaul: Whenever fuel injectors are removed for cleaning, testing, or repair, it's standard practice to inspect and replace shims to ensure proper reassembly and performance.
• Performance Decline: If the engine exhibits symptoms like reduced power, poor throttle response, or difficulty starting, worn shims may be contributing to improper nozzle positioning.
• Increased Fuel Consumption: A sudden drop in fuel economy may indicate inefficient combustion due to degraded spray patterns caused by compromised shim integrity.
• Emissions Failures: Elevated HC or NOx levels during emissions testing can point to incomplete combustion, potentially linked to misaligned injectors.
• After Major Engine Work: When cylinder heads are removed or replaced, injector shims should be rechecked and replaced as needed to maintain factory specifications.

Many manufacturers recommend replacing shims during scheduled maintenance intervals—typically every 100,000 to 150,000 miles for diesel engines or whenever injectors are serviced. Always consult your vehicle’s service manual for specific guidelines.

Q4: How to Tell If a Fuel Injector Adjustment Shim Is Bad?

Identifying a failing or damaged adjustment shim involves both diagnostic observation and physical inspection. Key indicators include:

• Abnormal Fuel Consumption: Either excessive fuel use or unexpectedly lean conditions may suggest improper fuel delivery due to incorrect nozzle protrusion.
• Increased Emissions: Black smoke (diesel) or rich exhaust smells (gasoline) often result from poor atomization caused by misaligned injectors.
• Engine Misfires and Rough Idling: Inconsistent fuel spray can lead to cylinder misfires, especially under load or during cold starts.
• Acceleration Hesitation: A lag or stumble when pressing the throttle may stem from delayed or uneven fuel injection.
• Visible Damage During Inspection: When injectors are removed, signs such as pitting, corrosion, warping, or scoring on the shim surface indicate it should be replaced.
• Compression or Leak-Down Test Anomalies: In some cases, incorrect nozzle seating due to shim wear can affect cylinder sealing and combustion efficiency.

Because shims are internal components, definitive diagnosis usually requires disassembly and measurement with precision tools such as micrometers or laser gauges. For accurate results and safe operation, it's best to have injector systems inspected and serviced by qualified technicians using OEM or certified replacement parts.