This is the Alliant Power AP53903, a common rail fuel injector remanufactured by Alliant Power for the Isuzu 4HK1 5.2L four-cylinder. It covers the 2005 to 2007 Isuzu NPR-HD, NQR and NRR, the 2005 to 2006 NPR and the 2005 to 2007 GMC W4500 and W5500. It replaces Isuzu 8973297035 (8-97329703-5), which is Denso 095000-5471. 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. Later 4HK1 trucks use different injectors: AP53907 for 2008 to 2010, and other numbers again after that.

Specifications

Fits / Applications

• Isuzu NPR-HD, NQR and NRR, 2005 to 2007, 4HK1 5.2L
• Isuzu NPR, 2005 to 2006, 4HK1 5.2L
• GMC W4500 and W5500, 2005 to 2007, 4HK1 5.2L
• Injector number Isuzu 8973297035 or Denso 095000-5471 only
• Four injectors per 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 AP53903  ·  Isuzu 8973297035 (8-97329703-5)  ·  Denso 095000-5471  ·  Later 4HK1 injector, 2008 to 2010 (different part) AP53907  ·  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 AP53903 fit my 2006 Isuzu NPR?

Yes, if it has the 4HK1 5.2L diesel and the old injector reads Isuzu 8973297035 or Denso 095000-5471. Call 530-668-0818 with the VIN if the number is hard to read.

What numbers does the AP53903 replace?

Isuzu 8973297035, also written 8-97329703-5, and Denso 095000-5471.

Does it fit a 2008 or newer NPR?

No. The 2008 to 2010 4HK1 is listed under AP53907 and later engines take other numbers again. A 2007 truck can go either way, so check the number on the old injector.

Is the AP53903 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

• 2008-2010 Isuzu NPR, NPR-HD, NQR & NRR 4HK1 5.2L Fuel Injector | Alliant Power AP53907 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.