Fuel Injector 3939826 for Cummins Engine 4B3.9 B4.5 B5.9 B6.7 6B5.9 ISB6.7 ISD4.5 QSB5.9
This fuel injector is engineered as a direct replacement for the Cummins Engine 4B3.9 B4.5 B5.9 B6.7 6B5.9 ISB6.7 ISD4.5 QSB5.9. 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 |
|---|---|
| Fuel Injector 3939826 for Cummins Engine 4B3.9 B4.5 B5.9 B6.7 6B5.9 ISB6.7 ISD4.5 QSB5.9 Condition: New Aftermarket Part Note: We recommend replacing the entire set of fuel injectors to ensure the engine’s optimal performance. Due to differences in oil output and atomization concentration between genuine and aftermarket parts, they should not be mixed. Replacing the entire set of injectors helps avoid potential issues. Always use clean oil. Replacement Part Number: 3939826, 0432191355 Fit For Yanmar Engine: 4B3.9, 6B5.9, B4.5, B4.5 CM2350 B129B, B4.5 CM2350 B147B, B4.5 RGT, B4.5S, B5.9 G, B5.9 GAS PLUS CM556, B5.9 LPG, B5.9 LPG PLUS CM556, B6.7 CM2350 B121B, B6.7 CM2350 B135B, B6.7 CM2350 B148B, B6.7 G CMOH6.0 B125, B6.7S, F3.8 CM2350 F120B, F3.8 F102, G3.9, G5.9, G5.9 CM558, ISB (CHRYSLER), ISB CM2150, ISB CM2150 E, ISB CM550, ISB CM850, ISB/ISD4.5 CM2150 B119, ISB/ISD4.5 CM2150 SN, ISB/ISD6.7 CM2150 B120, ISB/ISD6.7 CM2150 SN, ISB/ISD6.7 CM2880 B126, ISB3.9 CM2220 B107, ISB4.5 CM2150, ISB5.9G CM2180, ISB6.7 2010 DCX PICKUP, ISB6.7 2013 DCX CHASSIS CAB, ISB6.7 CM2150 SQ, ISB6.7 CM2250, ISB6.7 CM2350 B101, ISB6.7 CM2350 B103, ISB6.7 CM2350 B142, ISB6.7 G CM2180 B118, ISBE CM2150, ISBE CM800, ISBE2/ISBE3 CM850, ISBE4 CM850, ISD4.5 CM2150, ISD6.7 CM2880 D101, ISF2.8 CM2220, ISF2.8 CM2220 AN, ISF2.8 CM2220 EC, ISF2.8 CM2220 ECF2, ISF2.8 CM2220 F101, ISF2.8 CM2220 F117, ISF2.8 CM2220 F126, ISF2.8 CM2220 F129, ISF2.8 CM2220 IAN, ISF3.8 CM2220, ISF3.8 CM2220 AN, ISF3.8 CM2220 F103, ISF3.8 CM2220 F110, ISF3.8 CM2220 F116, ISF3.8 CM2220 IAN, ISF3.8 CM2350 F109, ISF4.5 CM2220 F123, ISG11 CM2880 G106, ISG11 CM2880 G108, ISG12 CM2880 G107, ISG12 CM2880 G109, ISG12 G CMOH6.0 G111, QSB3.9 30 CM550, QSB3.9 CM2880 B138, QSB4.5 30 CM550, QSB4.5 CM2150 B108, QSB4.5 CM2250 B131, QSB4.5 CM2250 EC, QSB4.5 CM2350 B106, QSB4.5 CM2350 B122, QSB4.5 CM2350 B144, QSB4.5 CM850, QSB5.9 30 CM550, QSB5.9 44 CM550, QSB5.9 CM2880 B115, QSB5.9 CM2880 B139, QSB5.9 CM550, QSB5.9 CM850, QSB6.7 CM2150 B109, QSB6.7 CM2250 | See product specifications |
Replaces OEM Part Numbers
3939826 • 0432191355 • Yanmar • Engine • 4B3.9 • 6B5.9 • CM2350 • B129B • B147B • B4.5S • CM556 • B121B
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 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 3939826 with 0432191355?
Yes. Both 3939826 and 0432191355 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 (CM556, CM558, CM550, CM850) 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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