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FASS Fuel System and the LB7 Injector Myth

Vinny Himes



Duramax Injectors Myths

In 2001 General Motors made some very drastic changes with their light duty diesel line up. It was time to end the 6.5L GM diesel engine.

It was under powered, noisy, and there were a lot of problems with the engines design. The mechanical injector of the 6.5L were swapped out for a common rail injection system. The common rail injection system used in the LB7 Duramax engine allowed General Motors to double the power output of their new diesel engine and fuel economy nearly doubled. If you own an LB7 Duramax you may have already replaced one set of injectors, or at least heard about how crappy their injectors are. This drives me nuts, there is nothing wrong with the LB7 injectors. The problem is with the GM fuel system. Isuzu originally designed the Duramax engine and joined efforts with General Motors at their Moraine Ohio assembly plant. So yes the engine was originally built by Isuzu but it is in fact assembled in the US by GM technicians.

Duramax Injectors, FASS Fuel System, LB7 Injector Failure, FASS Titanium,


When Isuzu put the engine together they went with the Bosch Duramax injectors and injection pumps because of Bosch’s unsurpassed quality of products. The thing that causes the injector failures is not Bosch’s fault or Isuzu’s fault. General Motors did not take into consideration that the Bosch Duramax injectors require 2 microns of filtration. When they designed the fuel system to accommodate the Duramax engine and Bosch fuel system they used an 8 to 12 micron fuel filter depending on where you get your replacement filters at. So right off the get go you are allowing particles 10 times larger than the injector can even handle; pass through them. This is the number 1 cause of injector failure in the common rail engines. POOR FILTRATION! Not bad injector design. The second thing GM screwed up for us, is the fuel supply to the injection pump. There is none…. I’m not sure how GM thought this was going to be a good idea. The Dodge Cummins common rail uses the exact same CP3 injection pump as the Duramax engine and very similar injectors. But Dodge uses a lift/supply pump to push the fuel from the tank all the way up to the CP3. This means the CP3 only has to do the job it was designed for (Feed the injectors with high pressure fuel)


Since GM didn’t use a lift pump the CP3 is trying to not only keep both fuel rails and all 8 injectors pressurized, but it is also trying to pull fuel from 10 feet away at the tank to keep it’s self full of fuel. This causes a lot of excess wear on the CP3 and the entire injection system. As the CP3 wears out, it will start to cavitate under heavy throttle. Cavitation is when the fuel isn’t being pulled or pushed in the proper volume to keep all the fuel lines full and the fuel becomes aerated. When air enters the fuel system it immediately causes irreparable damage.

So the best thing you can do for your LB7 Duramax, or any Duramax for that matter, is install an aftermarket lift pump that has the 2 micron filters built into it. Buying a $600 lift pump can save you thousands of dollars in repairs.

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  1. Avatar

    Jean-Francois martin

    02/27/2013 at 9:04 PM

    finally some one with the right answer and explaination ‘caus I am currently looking in buing a used 2500 hd chevy 2004 with a LB7 and to be honest the injector mith was a big concern to me here in canada you’re looking from 4500 to 5000$ to replace those injectors for my self I’m not a diesel mecanic but I will…

    • Vinny Himes

      Vinny Himes

      10/15/2018 at 12:51 PM

      I’m glad this article helped you my friend, feel free to hit me up with any other questions you may have.

    • Avatar


      08/16/2019 at 11:48 AM

      Hey there I have had my Lb7 since 2003 and I have been through 5 sets of injectors and all my sets didn’t last to 100,000 they went out around 58,000 miles when I bought the lift pumps which I have a air dog 4g I’m passed 100,000 miles on this set of injectors and it seems to run way smoother and better for me I currently have 407,668 miles on my truck

  2. Vinny L Himes

    Vinny L Himes

    02/28/2013 at 11:33 AM


    If you ever have any questions about your truck or a truck you are looking at purchasing feel free to send me an email or ask your questions here on our Forum. I am always happy to help with realistic answers and not a sales pitch!

    • Avatar

      Kartel teele

      06/20/2019 at 10:47 AM

      Hey Vinny, I have a question for you when you get the time. I have an 04 lb7 and I ran it out of fuel.. gauge isn’t working and couldn’t keep track of kms. Anyways I have changed fuel filter fuel housing unit and still won’t fire. Injectors are or were in great shape as truck ran perfect before with zero haze. Throwing a p0193 code but I also can’t get the truck running to scan if there’s more codes or delete etc. What I’ve come down too is I burnt out the cp3 in the truck. It sounds very dry motor when starting and almost as the pump is slapping around so my question for you is do you need a working CP3 for a FASS lift pump to pop the injectors or can the fass provide enough pump to replace the stock CP3

      • Vinny Himes

        Vinny Himes

        06/25/2019 at 12:22 PM

        Give me a call at the shop and I will be happy to run through some possible fixes for you. 770-267-3322 once we get it figured out, I will type out the solution here for our other readers.

  3. Avatar

    Tom Michelena

    02/28/2013 at 7:30 PM

    I have played with FASS and played with Air Dog. I fully support installing fass only on any turbo diesel. In my opinion, new trucks should come with these stock. Fuel filtration is critical. Do your truck a favor and install one today.

  4. Avatar

    Kyle Struiksma

    04/07/2013 at 4:10 PM

    What about Fuel lab and aeromotive?

  5. Vinny Himes

    Vinny Himes

    04/08/2013 at 11:10 AM

    Fuel Lab and Aeromotive make an excellent product. I have used them both on competition trucks, they move massive amounts of fuel and will keep up with the high demands of a competition injection pump.

    I have not used them on a daily driven street truck. I imagine they would work just fine as they can be regulated pressure wise. You can use an aftermarket filtration system in line with a Fuel Lab or Aeromotive fuel pump and have a similar product to a FASS pump.

  6. Avatar


    12/23/2013 at 7:23 AM

    IK that the Duramax does have a problem with poor filtration. A fuel pump can make a big difference in these trucks. I got a link that may help your readers. It is an articles about FASS’ new installation process. FASS now has a no frame drilling which is a huge help in installation.

    Article Link >>

  7. Avatar


    09/22/2014 at 9:54 AM

    Does the 2012 f250 w 6.7 powerstroke need the fast system. I have been debating doing a delete as I am in Texas, but I hear they are starting to check and give fines here this year. I just want my truck to last as I have 107k miles on it. What should I do to be completely as safe as possible?

  8. Avatar


    09/10/2015 at 11:44 AM

    I have been running a 1r-0750 cat filter on my lb7 sine 900 miles. I have still had my injectors fail. I do not have a lift pump. So if the injectors require a 2 micron filter then why did my injectors fail?

    • Vinny Himes

      Vinny Himes

      01/04/2017 at 3:42 PM

      The CAT filter helps eliminate dirt in the fuel, it doesn’t help with the air in the fuel and it doesn’t do anything to help take the strain off the injection pump, in fact making the injection pump try to pull fuel through an even more restrictive filter will cause it to work even harder than it is with a stock filter. The entire issue is caused by lack of supply, filtration is only part of the problem.

  9. Avatar


    12/26/2015 at 7:01 AM

    Hi i just recently purchased an 04 lb7 and injectors are failing truck is completely stock with a good fass system realistically how long will injectors last

    • Avatar

      Jim Perry

      12/03/2016 at 11:19 PM

      Look at hot shot secrets. They have some very good products. Superior high quality products. I have used some of their products in my 08 Duramax/ Allison Truck with excellent results. When I first used it I was about to give up on it when I started to notice that the turbo was loosening up and working like it should and the fuel additive works as well as the oil additive. After a few hundred miles it smoothed out and seemed to run as if i bought it brand new. I used the Transmission additive in the Allison tranny as well and it started shifting real smooth on the up shifts and the down shifts. Before you really couldn’t tell when it was shifting after about third gear. After the additive you could literally feel each and every shift. For a little while I thought I was going to get 100% of my money back due to their guarantee. I thought here we go again, wasted time and money. Boy am I glad I was wrong. Found a product worth their salt. Next up is the friction reducer and man I pray that it is at least haif as good as the other items have been. I am not a salesman for this company nor am I a paid person for the hot shots secret company. Their products helped me and I hope that they can help you. I will not use any other companies products in my Diesel Truck period.

    • Vinny Himes

      Vinny Himes

      01/04/2017 at 3:45 PM

      On a bone stock truck it is not uncommon for the injectors to start having issues between 85,000 to 100,000 miles. We work on thousands of trucks a year here at our shop, so those mileage numbers are based off what I see here at the shop. Some guys get 200,000+ out of the stock set, but those are very rare cases.

  10. Avatar


    05/09/2016 at 11:39 AM

    Hi, I just got my first diesel, a 2009 duramax the exhaust is deleted and it has a afe intake and a 90hp tune. Do these trucks need lift pumps too and better filters or did gm fix the problem by that year

    • Vinny Himes

      Vinny Himes

      05/09/2016 at 12:44 PM

      None of the Duramax’s have ever had a factory lift pump, we recommend them from 2001 through 2016.

  11. Avatar

    Randall Baker

    01/19/2017 at 2:31 PM

    Any suggestion for which replacement injectors to get. My 03 LB7 is out of commission and I am looking at replacing my self but they seem to be numerous brands.

    • Vinny Himes

      Vinny Himes

      01/20/2017 at 7:03 AM

      The best replacement we have found is straight from the local Chevy dealership. Either that or look around your area and see if there is a certified Bosch re manufacturer. The aftermarket world is flooded with junk remans that will not last. That job is very labor intensive and it’s not something you want to do twice. Saving money is usually a good thing, but cheaping out on LB7 injectors is not something I would recommend.

  12. Avatar

    Shawn Flynn

    09/29/2018 at 10:56 AM

    Hi Vinny,
    Absolutely the best “make sense” diesel site Period! I am old-poor and retiring! Bought a beautifully maintained 2003 GMC Sierra 2500HD LB7 turbo diesel 130K miles. Always wanted one… finally saved up and bought one. Checked the oil one day and found it was super high? Injectors were dumping fuel into the crankcase. Long story short, injector replacement was, well; “a mans got to know his limitations” moment. Something I just didn’t think I could do. So $6K in… had the injectors and delivery system replaced.
    My first thoughts, after the huge hit financially, was: fuel filtering? The injectors were hideously clogged. One was even cracked?
    Bottom line No amount of additives will “dissolve” clogging particles. Your advise is straight on…I did buy the fuel filter I could; a wicks but I don’t think it gets down to 2 microns of filtration.
    So after all my blustering what is you best advice on how to protect my injectors?
    Thank you for you valuable time – Helping others

  13. Avatar


    12/29/2018 at 5:52 PM

    Bought an 01 Chevy 2500 HD a few years ago, was blowing Oil vapors out the blowby tube, Not deisel. Engine oil was fine, injectors checked fine, compression was fine. Determined it was either the valve cover vents or valve in alternator bracket, or both that caused this condition. Sold the truck, didn’t have time to fool with it. Have you run across this condition? (I did tell the buyer what I’d determined the problem to be and later saw it running just fine.)

    • Vinny Himes

      Vinny Himes

      01/02/2019 at 7:57 AM

      Yes, this is very common. Those engines vent the CCV into the intake manifold. So it’s naturally under pressure. All diesel engines should have a little oil vapor venting from the crank case vent.

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