This is the Alliant Power AP53907, a common rail fuel injector remanufactured by Alliant Power for the Isuzu 4HK1 5.2L four-cylinder. It covers the 2008 to 2010 Isuzu NPR-HD, NQR and NRR and the 2008 to 2009 NPR. Two catalogs also list it for the 2007 to 2009 Isuzu FXR. AP53903 is the earlier 2005 to 2007 injector, and later trucks take other numbers again. A refundable core applies.

Hard starting, a rough idle, a miss under load, white or black smoke, fuel in the oil or a rail pressure fault all point at a worn common rail injector. Dirty fuel, water and a weak supply pump cause the same complaints, so check filters, fuel quality and rail pressure before you replace a set. The 4HK1 takes four injectors.

Specifications

Fits / Applications

• Isuzu NPR-HD, NQR and NRR, 2008 to 2010, 4HK1 5.2L
• Isuzu NPR, 2008 to 2009, 4HK1 5.2L
• Isuzu FXR, 2007 to 2009 (listed by two catalogs, confirm by injector number)
• Not for 2005 to 2007 trucks (AP53903). Later trucks take other numbers
• Four injectors per 4HK1 engine

Fit new fuel filters and make sure the tank and lines are clean before the engine runs. Keep every fuel connection capped until it is made up, use new sealing washers and O-rings, and torque the hold-downs and high-pressure lines to the Isuzu service manual figures.

Part Numbers & Cross Reference

Alliant Power AP53907  ·  Earlier 4HK1 injector, 2005 to 2007 (different part) AP53903  ·  Later 4HK1 injector (different part) AP53809

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

Will the AP53907 fit my 2009 Isuzu NPR?

It is listed for the 2008 to 2009 NPR and the 2008 to 2010 NPR-HD, NQR and NRR with the 4HK1 5.2L. Call 530-668-0818 with your VIN and the number on your old injector and we will confirm it.

How is the AP53907 different from the AP53903?

Both are Alliant Power remanufactured injectors for the 4HK1, but for different years. AP53903 is listed for 2005 to 2007 and AP53907 for 2008 to 2010. Later trucks take other numbers again. Do not mix them in one engine.

Does the AP53907 fit the bigger 7.8L trucks?

Two catalogs list it for the 2007 to 2009 Isuzu FXR. For any 6HK1 truck, send us the number on the old injector first, because that engine used several injectors.

Is the AP53907 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.

Related Parts

• 2005-2007 Isuzu NPR-HD, NQR, NRR & GMC W4500 4HK1 5.2L Fuel Injector | Alliant Power AP53903 Remanufactured
• 2003 Isuzu FTR, FVR, Chevy Kodiak & GMC TopKick 6HK1 7.8L Fuel Injector | Alliant Power AP53801 Remanufactured
• 2007-2009 Chevy Kodiak C6500, C7500 & T-Series Isuzu 6HK1 7.8L Injector | Alliant Power AP53906 Remanufactured
• Isuzu 4LE2 2.2L Tier 4 RHF3 Turbocharger | IHI F31CAD-S0182B New (Isuzu 8982236170)
• Common Rail Diesel Injector Testing & Rebuild Service

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.