Injector Fuel Supply Tube 3930393 for Cummins Engine 6C8.3 QSB6.7 ISBE4 ISC8.3 ISL9
This fuel injector is engineered as a direct replacement for the Cummins Engine 6C8.3 QSB6.7 ISBE4 ISC8.3 ISL9. 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 |
|---|---|
| Cummins Engine 6C8.3 QSB6.7 ISBE4 ISC8.3 ISL9 Replacement Part Number: 3930393 Fit for | See product specifications |
| Cummins Engine: 6C8.3, ISBE4 CM850, ISC8.3 CM2250, ISL9 CM2250, ISL9 CM2350 L101, QSB6.7 CM850, QSC8.3 CM554, QSC8.3 CM850 Application:Fit for following models | See product specifications |
| Hyundai Excavator: R320LC | 7, R330LC-9S, R300LC-9S, R320LC7, R330LC9S, R300LC9S |
| Hyundai Loader: HL760 | 9S |
Replaces OEM Part Numbers
3930393 • Cummins • Engine • 6C8.3 • ISBE4 • CM850 • ISC8.3 • CM2250 • CM2350 • QSB6.7 • QSC8.3 • CM554
Signs You Need a Replacement
If your equipment is showing any of these symptoms, the fuel line may be the cause:
- Rough idle or misfire — Uneven fuel delivery from a worn injector causes the engine to shake at idle. On Cummins 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 Cummins 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
Which Cummins models does this part fit?
Refer to the Vehicle Compatibility table above for the full list of Cummins models. Each listing includes the body type, engine, and production years. Match your vehicle’s engine code (stamped on the engine block) against the listed codes to confirm.
Can I cross-reference 3930393 with Cummins?
Yes. Both 3930393 and Cummins 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 (CM850, CM554, HL760) 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.
What are the common failure signs on a Cummins engine?
On Cummins 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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