October 22, 2018

FASS Fuel System and the LB7 Injector Myth

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. Jean-Francois martin

    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…

  2. Tom Michelena

    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.

  3. Vinny Himes
    Vinny Himes

    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.

  4. Jim

    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 >>

  5. john

    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?

    1. Vinny Himes
      Vinny Himes


      A Fass will benefit any diesel truck, although the 6.7’s do have a very good fuel pump from the factory, they don’t offer removal of the air from the fuel. That’s where the Fass shines through. You will certainly want to run a sump with it though, the 6.7 pumps run at 65 psi and they are loud without a sump.


  6. Marc

    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?

    1. Vinny Himes
      Vinny Himes

      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.

  7. Mario

    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

    1. Jim Perry

      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.

    2. Vinny Himes
      Vinny Himes

      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.

  8. Mario

    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

  9. Randall Baker

    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.

    1. Vinny Himes
      Vinny Himes

      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.

  10. Shawn Flynn

    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


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