129978-11871 Genuine Yanmar Injector Chamber Gasket – MIU802096

Description

Genuine Yanmar 129978-11871 Injector Chamber Gasket

Genuine Yanmar replacement injector chamber gasket, part number 129978-11871, for select Yanmar common-rail diesel engines.

This gasket fits around the injector body in the cylinder-head or injector-chamber area. It is used on Yanmar engines installed in tractors, excavators, skid steers, loaders, commercial mowing equipment, generators, marine applications, and other industrial diesel machinery.

The same gasket is commonly cross-referenced to John Deere MIU802096. It may also be associated with earlier Yanmar reference 129978-11870.

Sold individually. Most applications require one 129978-11871 gasket per injector. A three-cylinder engine normally uses three, while a four-cylinder engine normally uses four.

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Product Specifications

• Brand: Genuine Yanmar
• Yanmar part number: 129978-11871
• Related Yanmar number: 129978-11870
• John Deere cross-reference: MIU802096
• Part type: Injector chamber gasket / injector body gasket
• Fuel-system type: Common-rail diesel injection
• Installation location: Injector and cylinder-head chamber area
• Fuel type: Diesel
• Condition: New
• Package quantity: One gasket
• Typical quantity required: One per injector

Verify the original part number, engine model, and engine serial number before ordering.

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Important: This Is Not the Lower Injector Tip Washer

Yanmar uses more than one sealing component around the injector assembly.

• 129978-11871: Injector chamber or injector body gasket shown in this listing
• 120270-54410: Separate injector washer used lower in the injector installation

The two parts have different shapes, locations, and functions. Do not order 129978-11871 solely because you need a generic “injector tip washer” or copper nozzle seal.

If the old part being replaced is a thin metal or copper washer located directly beneath the injector tip, verify whether the application requires 120270-54410 or another engine-specific injector washer.

This listing is specifically for Yanmar gasket number 129978-11871.

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What Does the Injector Chamber Gasket Do?

The 129978-11871 gasket provides the specified seal around the injector body where it passes into the cylinder-head and injector-chamber area.

It helps maintain the original injector installation and closes the space around the injector body. The gasket should be inspected whenever an injector is removed for testing, replacement, cylinder-head service, or engine repair.

An old gasket may become:

• Compressed from previous installation
• Hardened by engine heat
• Torn during injector removal
• Damaged by carbon or debris
• Distorted from incorrect installation
• Missing after previous injector service

Replacing the gasket while the injector is already removed helps restore the original sealing arrangement and avoids repeating the injector-removal procedure later.

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Common Reasons to Replace the Injector Gasket

The 129978-11871 gasket is commonly replaced during:

• Common-rail injector replacement
• Injector testing or rebuilding
• Cylinder-head removal
• Cylinder-head gasket replacement
• Valve or rocker-arm service
• Engine overhaul
• Repair of contamination around the injector bore
• Replacement of damaged injector hold-down hardware
• Installation of a new or remanufactured injector

Injector installation gaskets should be compared carefully with the original components. Several similar-looking seals and washers may be used on the same injector assembly.

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Yanmar Part Numbers and Cross References

• 129978-11871
• 12997811871
• 129978-11870
• 12997811870
• 4T-12997811871
• 4T12997811871
• VV12997811871
• Y129978-11871
• Y12997811871
• John Deere MIU802096
• A-MIU802096

Reference numbers are provided to help identify the part. Confirm the current number in the applicable engine or equipment parts catalog.

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Common Yanmar Industrial Engine Applications

The 129978-11871 injector gasket is used on many Yanmar TNV common-rail engine configurations, including select:

• Yanmar 3TNV86CT
• Yanmar 3TNV88C
• Yanmar 3TNV88C-DDT
• Yanmar 3TNV88C-DTR
• Yanmar 4TNV86CT
• Yanmar 4TNV88C
• Yanmar 4TNV88C-STB1
• Yanmar 4TNV94FHT
• Yanmar 4TNV98C
• Yanmar 4TNV98CT
• Yanmar 4TNV98CTL

Yanmar engine suffixes identify specific equipment, emissions, fuel-system, and installation configurations. Match the complete engine model and serial number rather than relying only on the base engine family.

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Yanmar Marine Engine Applications

Yanmar marine parts catalogs also list 129978-11871 in the cylinder-head and injector assemblies of select newer JH common-rail engines, including:

• Yanmar 3JH40
• Yanmar 4JH45
• Yanmar 4JH57
• Yanmar 4JH80
• Yanmar 4JH110

These engines may be used as marine propulsion engines, auxiliary engines, or generator engines. Verify the full engine designation and serial number before ordering.

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John Deere MIU802096 Cross Reference

Yanmar 129978-11871 is commonly cross-referenced to John Deere injector gasket MIU802096.

John Deere uses this gasket on a broad range of equipment powered by compatible Yanmar engines. Applications may include compact tractors, excavators, skid steers, compact track loaders, wheel loaders, and commercial mowing equipment.

Common John Deere Compact Tractor Applications

• John Deere 2032R
• John Deere 2038R
• John Deere 3032E
• John Deere 3033R
• John Deere 3035D
• John Deere 3036E
• John Deere 3038E
• John Deere 3039R
• John Deere 3043D
• John Deere 3046R
• John Deere 4044M
• John Deere 4044R
• John Deere 4052M
• John Deere 4052R
• John Deere 4066M
• John Deere 4066R
• John Deere 4075R

Common John Deere Excavator Applications

• John Deere 50P
• John Deere 50G
• John Deere 60P
• John Deere 60G
• John Deere 75P
• John Deere 75G
• John Deere 85P
• John Deere 85G
• John Deere 210G
• John Deere 210L EP

Common John Deere Skid Steer and Compact Track Loader Applications

• John Deere 312GR
• John Deere 314G
• John Deere 316P
• John Deere 316GR
• John Deere 317P
• John Deere 317G
• John Deere 318P
• John Deere 318E
• John Deere 318G
• John Deere 319E
• John Deere 320E
• John Deere 320G
• John Deere 323E
• John Deere 324P
• John Deere 324E
• John Deere 324G
• John Deere 325G
• John Deere 326P
• John Deere 326E
• John Deere 328E
• John Deere 329E
• John Deere 330P
• John Deere 330G
• John Deere 331P
• John Deere 331G
• John Deere 332E
• John Deere 332G
• John Deere 333P
• John Deere 333E
• John Deere 333G
• John Deere 334P
• John Deere 335P

Common John Deere Loader Applications

• John Deere 184G
• John Deere 204G
• John Deere 204L
• John Deere 244P
• John Deere 244K
• John Deere 244K-II
• John Deere 244L
• John Deere 304G
• John Deere 304L
• John Deere 310G
• John Deere 310L EP
• John Deere 324K
• John Deere 324L

Common John Deere Turf Equipment Applications

• John Deere 1570
• John Deere 1575
• John Deere 1580
• John Deere 1585
• John Deere 1600 Turbo Series III
• John Deere 7400A
• John Deere 7500A E-Cut
• John Deere 7500A PrecisionCut
• John Deere 7700A E-Cut
• John Deere 7700A PrecisionCut
• John Deere 8000A E-Cut
• John Deere 8700A PrecisionCut
• John Deere 8800A
• John Deere 8900A
• John Deere 9009A
• John Deere Z997R

John Deere models can have serial-number breaks and different engine configurations. Confirm MIU802096 in the machine-specific parts catalog before ordering.

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Other Equipment Applications

Compatible Yanmar TNV engines are installed in equipment sold under many brand names. Published application information also associates this gasket with select:

• Hitachi compact excavators
• Gehl compact equipment
• ASV equipment
• Yanmar compact excavators
• Yanmar wheel loaders
• Industrial generators
• Commercial mowing equipment
• Material-handling and construction equipment

The equipment brand alone does not confirm fitment. Match the Yanmar engine model, engine serial number, injector arrangement, or original gasket number.

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How Many Gaskets Are Required?

Yanmar parts diagrams generally show one 129978-11871 gasket for each injector.

• Three-cylinder engine: Normally three gaskets
• Four-cylinder engine: Normally four gaskets

This listing is for one individual gasket unless a different quantity is selected.

When replacing a complete set of injectors, order enough gaskets for every cylinder and verify whether the separate lower injector washers are also required.

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When Should the Injector Gasket Be Replaced?

Consider replacing the 129978-11871 gasket whenever:

• An injector is removed from the cylinder head
• A new or remanufactured injector is installed
• The injector chamber is cleaned
• The cylinder head is removed or rebuilt
• The old gasket is compressed, torn, hardened, or missing
• Injector hold-down components are replaced
• The engine is undergoing a complete overhaul

Do not reuse a visibly damaged or permanently compressed injector gasket.

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How to Confirm Fitment

Before ordering, check:

• The number on the original gasket package or parts invoice
• The complete Yanmar engine model
• The Yanmar engine serial number
• The equipment make, model, and serial number
• The injector part number
• The engine parts diagram
• Whether the parts catalog specifies 129978-11871 or MIU802096
• Whether you need the chamber gasket or the separate lower injector washer

The equipment model alone may not identify the correct gasket because manufacturers can change engines or injector systems during production.

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Installation Notes

• Clean loose dirt and debris from around the injector before disassembly.
• Follow the engine manufacturer’s common-rail fuel-system safety procedures.
• Do not loosen high-pressure fuel lines while the engine is running.
• Cap open fuel lines and injector connections immediately after removal.
• Remove the old injector gasket and any remaining debris from the chamber.
• Do not scratch the injector body or cylinder-head sealing surfaces.
• Compare the new gasket with the original before installation.
• Install the gasket in the correct location and orientation shown in the service manual.
• Inspect the separate lower injector washer and replace it when required.
• Use the specified injector hold-down procedure and tightening torque.
• Replace any one-time-use fuel-line or injector components specified by Yanmar.
• After assembly, check for fuel, oil, or compression leakage around the injector area.

Modern common-rail diesel systems operate at extremely high pressure. Injector service should be performed by someone familiar with common-rail fuel systems and the applicable Yanmar service procedure.

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Why Use a Genuine Yanmar Injector Gasket?

• Correct Yanmar part number 129978-11871
• Designed for the original injector and cylinder-head arrangement
• Known cross-reference to John Deere MIU802096
• Used across a broad range of Yanmar common-rail engines
• Suitable for professional injector replacement and engine repair
• Correct service component for Yanmar TNV and JH applications

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Fitment and Trademark Notice

Yanmar, John Deere, Hitachi, Gehl, ASV, equipment models, engine models, and reference numbers are used for identification and fitment purposes. Verify the engine-specific parts information before ordering.

See the other Yanmar parts we have listed

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