The AP55597 is a common-rail fuel injector remanufactured by Alliant Power for Cummins QSB4.5, QSB5.9 and QSB6.7 industrial engines. It replaces Cummins 5263262 (also 4945969 and 3976372) and Komatsu 6754-11-3011, and it crosses to new Bosch 0445120231 and to Bosch remanufactured 0986435597. Sold as one injector; the QSB4.5 takes four and the QSB5.9 and QSB6.7 take six.

We list the same injector two other ways: new as Bosch 0445120231, and as 0986435597, Bosch Authorized Remanufactured by Valley Fuel Injection & Turbo. All three cover the same engines. Replace an injector when hard starting, rough running, smoke or low power traces back to it, and clean up the fuel first, since dirt and water are what usually kill common-rail injectors. Other QSB injectors look the same, for example Bosch 0445120251 (Cummins 5263314) on the QSB6.7 and Bosch 0445120252 (Cummins 5263315) on the QSB5.9, so match the number. A refundable core applies to this injector.

Specifications

Fits / Applications

• Cummins QSB4.5 common-rail industrial engines
• Cummins QSB5.9 common-rail industrial engines
• Cummins QSB6.7 common-rail industrial engines
• Komatsu equipment that calls for Komatsu injector 6754-11-3011
• QSB engines were also built with other injector numbers, so match the number on your old injector or send us the engine serial number (ESN)
• Four injectors on the QSB4.5, six on the QSB5.9 and QSB6.7

Fit new seals on each injector and check the high-pressure connector (feed) tube for wear or damage before it goes back in. Change the fuel filters and clear any dirty or watered fuel before start-up.

Part Numbers & Cross Reference

Cummins 5263262  ·  Cummins (suffix versions) 5263262NX, 5263262PX, 5263262RX  ·  Cummins 4945969  ·  Cummins 3976372  ·  Komatsu 6754-11-3011  ·  Bosch (new) 0445120231  ·  Bosch (alternate) 0445120059  ·  Bosch remanufactured 0986435597

Cross-reference numbers can change with engine serial, build year and emissions tier, so treat this list as a starting point. Send us your engine serial number and we will confirm the exact match against your build before anything ships. That check is free and takes a few minutes.

Frequently Asked Questions

Which engines does the AP55597 fit?

Cummins QSB4.5, QSB5.9 and QSB6.7 industrial engines that call for Cummins injector 5263262. These engines were also built with other injectors that look alike, so call 530-668-0818 with your engine serial number (ESN) and we will match it.

What numbers does the AP55597 cross to?

Cummins 5263262, 4945969 and 3976372, Komatsu 6754-11-3011, new Bosch 0445120231 (also 0445120059) and Bosch remanufactured 0986435597.

Is the AP55597 new or remanufactured, and is there a core?

It is remanufactured by Alliant Power. A refundable core applies, and it comes back when we receive your old injector in rebuildable condition.

How many AP55597 injectors does my engine take?

It is sold as one injector. The QSB4.5 takes four, and the QSB5.9 and QSB6.7 take six.

Related Parts

• Cummins QSB4.5, QSB5.9 & QSB6.7 Common-Rail Fuel Injector | Bosch 0445120231 New (Cummins 5263262)
• Cummins QSB6.7 & ISB6.7 Common-Rail Fuel Injector | Alliant Power AP55177 Remanufactured (Cummins 5254261)
• Cummins QSB 5.9L Common-Rail Fuel Injector | Bosch 0445120254 New (Cummins 5263317)
• Cummins QSB 4.5 & QSB 6.7 Tier 3 CP3 Injection Pump | Bosch 0445020122 New (Cummins 5256607)

Why Buy From Valley Fuel Injection

We are a diesel fuel-injection and turbocharger shop in Woodland, CA, rebuilding pumps, injectors and turbos on our own benches since 1993, not a drop-ship storefront. When you call, you talk to the people who test these units. We verify fitment against your engine serial, VIN or build date before anything ships, so the right part arrives the first time.

Not sure the injectors are the problem? We test and diagnose in-house before you buy. See our common rail injector testing and rebuild service.