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Duramax First Generation: 2001-2004 (LB7) Discuss the first generation (2001-2004 LB7) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 01-09-2017, 08:58 PM   #1 (permalink)
Mjfulmer
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2003 lb7 rough idle noisy operating

Hey guys long time looker first time poster!
So I've got a 2003 lb7 ccsb with the Allison. Bought last year and 26 days after purchase the crank snapped. Which lead to a complete tear down and rebuild. Truck ran perfect for about 300 miles and I started having a rough idle. That progressed very quickly to horrible idle and a pretty bad fuel knock. Rebuilt the fuel filter head. Put a AC Delco filter on it. Helped very little. Changed fuel pressure regulator with an eBay one helped a lot but still had a lot of noise. Pressure readings were a little weird so I replaced the fuel pressure sensor. Much better for a little while. Now it's still very noisy operating at any temp. Cold, normal. Same noise. Seems to have an intermittent surge at idle but I can put it in gear and it clears up. I'm stumped so I've decided to come to the pros for help! I'm all ears. Injectors all check out well within spec.

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Old 01-10-2017, 02:03 AM   #2 (permalink)
Rambos_Ride
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I've only had my 2002 for a week so I can't be much help.

I am curios about the crank failure, was there any indication why it failed? Also, did you learn (or does anyone know) if this is a weak point to the LB7?

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Old 01-10-2017, 02:15 PM   #3 (permalink)
SpikeDmax
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How much was your FPR off ebay? I'm guessing around $100? There are known counterfeits out there. Not saying that's your problem but something to consider. A genuine Bosch FPR I believe is around $200
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Toyo MT 285/75/16, Nicktane filter, Neoprene seat covers, Bilsteins 5100, 2nd owner @85k. 200k Nov. 2015. Do all my own work and looking forward to handing my son the keys soon.
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Old 01-10-2017, 07:29 PM   #4 (permalink)
Mjfulmer
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Nope just running down the interstate about 70. And she decided to be a 2 piece crank! Dowel pin bent n broke off. And yes sir right at 100 bucks. Could that be my issue?
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Old 01-11-2017, 05:52 AM   #5 (permalink)
MANICK
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We offer a Fuel Pressure Regulator Kit. it comes with a new Bosch regulator, new bolts and the o-ring and gasket needed to do the job.


Fuel Pressure Regulator Kit, LB7, 2001-2004

We also offer a full reman pump. If it's a higher mileage, up over 250,000, I'd seriously think about looking at a pump. (which comes with a new regulator on it.)

Duramax CP3 Injection Pump LB7

CP3 Fuel Injection Pump Install Gasket Kit, LB7, 2001-2004
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Old 01-11-2017, 01:17 PM   #6 (permalink)
SpikeDmax
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If your idle is fluctuating up and down fairly dramatically, it's most likely the FPR. If it were me and you have the funds and capability replace the CP3 with a new FPR.
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2001 GMC Dmax/Ally 2500HD CC, built Trans @ 160k, injectors @ 109k. 196k. ProFab turbo horn, air box mod, Power sliding rear window, Leer Canopy,
Hot Edge/Attitude & Trippin mount, Rhino lined bed,
Toyo MT 285/75/16, Nicktane filter, Neoprene seat covers, Bilsteins 5100, 2nd owner @85k. 200k Nov. 2015. Do all my own work and looking forward to handing my son the keys soon.
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