The Alliant Power AP55128 is a remanufactured XPI common-rail fuel injector for Cummins X15 and ISX15 engines built to EPA17 through EPA24 emissions. It replaces Cummins 5579421, 4327147 and 4384365, plus the newer 6513589 and 6513590 numbers. It comes with a new high-pressure connector (supply) tube.

It is not the same injector as the earlier ISX15 units, AP55101 for EPA10 and AP55100 for EPA13, even though they look alike. Worn XPI injectors cause hard starts, rough idle, a miss, smoke, low power and injector fault codes. Each injector has its own trim code, which must be entered with a scan tool after install.

Specifications

Fits / Applications

• Cummins X15 engines built to EPA17 through EPA24 (confirm by CPL)
• Cummins ISX15 engines built to EPA17 or later (confirm by CPL)

Clean the injector bore before the new injector goes in, and keep the open fuel system capped. Lube the injector O-ring with clean engine oil. Always fit a new high-pressure connector (feed) tube with the injector; one comes in the box. Start the hold-down bolt, seat the connector tube, then torque the hold-down bolt and the connector tube nut in stages (pre-torque both, then final torque) to Cummins specs. Route the injector harness clear of the rocker levers and engine brake. Enter each injector’s trim code with a scan tool; the label on the injector shows the part number, serial number and trim code. Change the fuel filters at the same time.

Part Numbers & Cross Reference

Cummins 5579421  ·  Cummins 5579421PX  ·  Cummins 5579421RX  ·  Cummins 4327147  ·  Cummins 4327147PX  ·  Cummins 4327147RX  ·  Cummins 4384365  ·  Cummins 4384365PX  ·  Cummins 6513589  ·  Cummins 6513589PX  ·  Cummins 6513590

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 Cummins engines take the Alliant Power AP55128 injector?

Cummins X15 and ISX15 engines built to EPA17 through EPA24 emissions. Order by CPL or ESN, not by the name ISX15, because EPA10 and EPA13 ISX15 engines take different injectors.

What Cummins numbers does AP55128 replace?

Cummins 5579421, 4327147 and 4384365, plus the newer 6513589 and 6513590 numbers.

Is AP55128 the same injector as AP55101 or AP55100?

No, even though they look alike. AP55101 (Cummins 5579417) is for EPA10 ISX15 engines and AP55100 (Cummins 5579419) is for EPA13. Call 530-668-0818 with your engine serial number (ESN) and CPL and we confirm the match at no charge before anything ships.

What comes with the AP55128, and is there a core charge?

The box holds the remanufactured injector and a new high-pressure connector (supply) tube. A refundable core charge is added at checkout and refunded when we receive your rebuildable core. Each injector has its own trim code, which must be entered with a scan tool after install.

Related Parts

• Cummins ISX15 EPA10 XPI Common-Rail Fuel Injector | Alliant Power AP55101 Remanufactured
• Cummins ISX12 XPI Fuel Injector | Alliant Power AP55103 Remanufactured
• Cummins ISX12 XPI Fuel Injector Set of 6 | Alliant Power AP55103 Remanufactured

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. Confirm fitment against your engine serial, VIN or build date before you order. Call us and we will help you match the right part.