CUMMINS 3900808 GENUINE FUEL INJECTOR SEALING WASHER (9MM) FOR 1989-1991 & COMPETITION CUMMINS ENGINES

The Cummins 3900808 fuel injector sealing washer is an OEM copper washer designed for 1989-1991 Dodge Ram 5.9L Cummins engines. It provides a proper seal between the fuel injector and cylinder head, preventing combustion gas leaks and maintaining correct injector spray pattern.

This washer also fits competition Cummins engines running 9mm injector tips, making it a must-have for performance builds, sled pulling, and drag racing applications.

Features & Benefits

• OEM Quality: Genuine Cummins part ensures precise fit and long service life.
• Sealing Performance: Copper washer prevents leaks under high combustion pressure.
• Versatile Use: Fits both stock 1989-1991 5.9L Cummins and competition 9mm injector builds.

Fitment

• 1989-1991 Dodge Ram 5.9L Cummins 12-valve (VE pump, 9mm injector tips)
• Competition Cummins engines with 9mm injector tips

Cross Reference Part Numbers

• Cummins 3900808
• Aftermarket equivalents: M-3900808

Frequently Asked Questions

Do I need to replace injector washers when installing new injectors?

Yes. Always replace sealing washers during injector installation to ensure proper sealing and combustion efficiency.

Are these washers reusable?

No. Copper crush washers should never be reused. Always use new ones when removing injectors.

Do these work with aftermarket injectors?

Yes, as long as the injectors use 9mm tips, including high-performance racing injectors.

Maintenance Note

Pro Tip: Pair new injector washers with fresh Cummins fuel injectors and check out our Pulling & Racing Products section for performance-focused upgrades.

Related Categories

• 1989-1993 Cummins Gaskets & Seals
• Cylinder Head Gaskets
• Timing Gear Case & Covers
• Oil Pans & Components
• All Dodge Cummins Categories

Tags

cummins 3900808, 9mm injector washer cummins, cummins injector sealing washer, 5.9 cummins injector washer, dodge ram injector washer, cummins racing injector washer, competition cummins injector washer, copper injector washer cummins

Fitment

• 1989 Dodge Ram 2500/3500 5.9L Cummins
• 1990 Dodge Ram 2500/3500 5.9L Cummins
• 1991 Dodge Ram 2500/3500 5.9L Cummins

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