6 Pieces Fuel Injector Nozzle 7S-9891 7S-8722 8N-4694 8N-8796 for Caterpillar CAT Engine 3406 3408 3412 3304 3306 1673C

6 Pieces Fuel Injector Nozzle 7S-9891 7S-8722 8N-4694 8N-8796 for Caterpillar CAT Engine 3406 3408 3412 3304 3306 1673C

This fuel injector is engineered as a direct replacement for the Caterpillar CAT Engine 3406 3408 3412 3304 3306 1673C. Manufactured to meet or exceed OEM specifications, it delivers reliable performance in demanding conditions. Each unit is tested for fuel flow, pressure rating, and durability before leaving the factory to ensure consistent quality across every order.

Vehicle Compatibility

Replaces OEM Part Numbers

CA7S9891 • 7S-9891 • 7S9891 • CA7S8722 • 7S-8722 • 7S8722 • CA8N4694 • 8N-4694 • 8N4694 • CA8N8796 • 8N-8796 • 8N8796

Signs You Need a Replacement

If your equipment is showing any of these symptoms, the injectors & nozzle may be the cause:

• Rough idle or misfire — Uneven fuel delivery from a worn injector causes the engine to shake at idle. On Caterpillar engines, this is often accompanied by a knocking sound under load.
• Black or white exhaust smoke — Black smoke means excess fuel; white smoke indicates incomplete combustion. Both point to injector spray pattern degradation.
• Loss of engine power — A single failing injector reduces cylinder output. Multi-cylinder engines lose noticeable power when one injector flows less than the rest.
• Increased fuel consumption — Poor atomization means the engine burns more fuel to produce the same power. Monitor your fuel burn rate as an early warning sign.
• Hard starting or no start — If the injector doesn’t deliver fuel on cranking, the cylinder won’t fire. This is especially common in cold weather with worn nozzles.
• Fuel in engine oil (dilution) — Fuel leaking past the injector seat seal contaminates the crankcase oil. If the oil level rises or smells of diesel, inspect the injectors immediately.

Replace as a Set

Replace all injectors as a set whenever possible. On Caterpillar engines, mixing old and new injectors creates uneven fuel delivery — the new injectors compensate for the worn ones, shortening their life. When installing, use new copper sealing washers and torque to the specification in the service manual. After installation, run the engine at idle for 5 minutes to bleed air from the fuel system, then check for leaks at each injector connection before putting the machine under load.

Frequently Asked Questions

Will this fit my Caterpillar 3406?
Yes. This part is designed to fit the Caterpillar 3406, 3408, 3412, 3304 among other models listed in the compatibility table above. Verify your specific model and engine code before ordering to ensure the correct fit.

Can I cross-reference CA7S9891 with 7S-9891?
Yes. Both CA7S9891 and 7S-9891 are interchangeable OEM numbers for this part. They refer to the same component with the same specifications, just different part number revisions.

This listing is for 6 pieces – do I need to buy a full set?
This listing includes 6 units. For best results, replace all injectors at the same time rather than one at a time. Mixing old and new units causes uneven fuel delivery and shortens the life of the new parts.

What are the common failure signs on a Caterpillar engine?
On Caterpillar engines, watch for black exhaust smoke under load, rough idle, misfire codes (P0300 series), and loss of power. A single failing injector can reduce engine output by up to 25%. If you notice fuel in the engine oil, the injector seat seal is likely compromised.

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