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.
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.