6 Pcs Fuel Injector 321-0990 for Caterpillar CAT Engine C6.6 Wheel Tractor 613G
This fuel injector is engineered as a direct replacement for the Caterpillar CAT Engine C6.6 Wheel Tractor 613G. 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
| Application | Details |
|---|---|
| Caterpillar | See product specifications |
| CAT Engine:C6.6 Application:Fit for following models | See product specifications |
| CAT Asphalt Paver:AP | 1000E,AP-1055E |
Replaces OEM Part Numbers
321-0990 • 10R-7668 • 3210990 • 10R7668 • CA3210990 • CA10R7668 • Caterpillar • Engine • Application • following • models • Asphalt
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 613G?
Yes. This part is designed to fit the Caterpillar 613G 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 321-0990 with 10R-7668?
Yes. Both 321-0990 and 10R-7668 are interchangeable OEM numbers for this part. They refer to the same component with the same specifications, just different part number revisions.
How do I check if my engine code (UP613G) matches?
The engine code is stamped on a metal tag attached to the engine block, usually near the timing belt cover or on the cylinder head. Compare the code you find with the list above. Engine codes are 3 to 6 characters long.
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.
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