BASIC QUESTIONS ABOUT DURAMAX LB7 INJECTOR SERVICE

Hello, I have a 2002 LB7, with 143,000 miles on the truck's odometer. The dealership replaced the injectors the first time at 80,000 miles (under warranty) with (I'm assuming) remanufactured injectors. Now after another 50k I'm getting black smoke at the tailpipe at idle. No increase in oil level, or fuel smell in oil.

Anyway, here are my questions: 1) I was told that I could buy some time before injector replacement by using additional additives. The recommendation was to use Hot Shot Diesel Extreme. Any better ideas, or will additives at this point do anything? 2) I'd like to do the injector replacement myself, but need info on special tools for injector and cup removal and whether it's necessary to remove injector cups, or not...

Appreciate any help you can provide...

Vetman7 Via Email

Hello,

We've been doing this diesel thing for a long time, and the question regarding the benefits of diesel fuel treatment has been hashed and re-hashed many-many times. Here's what I think... Personally, I believe a nationally available fuel treatment is worthwhile IF the treatment includes a cetane improver in the list of ingredients. Large fleet tests have proven that fuel economy is increased enough to pay for the cost of treatment – meaning any other benefits, like fuel injection system cleaner and lubricity are basically free. Be aware that individuals have a hard time being able to document an improvement in fuel economy because of the limited time and often dramatic seasonal temperature/ weather changes - just not enough good data – though I believe the fuel economy bump is still there regardless. What's not easily proven is whether a treatment extends the life of fuel injection components... There's just no way to be sure - no

positive proof either way – based on injection system service communications with many thousands of diesel pickup owners. Can a fuel treatment clean the internal components of the fuel system, removing varnish or other fuel-related residue that can negatively affect injector performance? Sure -maybe, but proof that shows a fuel system cleaner extends injector life is really hard to come by. I have a couple of anecdotal reports that are pretty convincing, but... Industrialinjection.com has been offering "screw-in" LB7 injector cups for some time now. I wrote about screw-in cups as a "I wish this existed" product some years ago. Now it's a reality. They're not cheap, but it would remove the angst over whether that excess pressure in the cooling system LB7 owners might see is due to a cup seal leak or a head gasket leak. You'd be surprised/horrified to read as many reports as I have from everyday LB7 owners about over-pressurized cooling systems in the days/weeks/months following an injector replacement in these LB7S - too many to be coincidence. I think the cup sealant gets disturbed in those cases, and begin leaking combustion pressure into the cooling system. It's a frustrating and disappointing discovery after paying someone thousands of dollars to install a new set of injectors (or new head gaskets are installed thinking that's the problem).

I've spoken to many long time Duramax mechanics through the years, both GM certified and independent shop mechanics about this very issue (cup seal leaks when/after changing injectors). About a third of them reseal every cup that had its injector removed. The rest don't reseal any of them unless they "see" the cup move when removing the injector.

Personally, I'd spend the extra time/money to re-seal every injector cup when installing new injectors… Or, just install the Industrial Injection cups with threaded ends during the re-assembly. You'll find all of the special tools needed for replacing the injectors and injector cups at Amazon and ebay. Just enter the search terms “Duramax injector cup tools” in the search line on either site.

I'm hoping to do a head gasket and Industrial Injection cup install later this summer. I want the engine in my LB7 truck to be as trustworthy as it was when I bought the truck brand new in December of 2000. Everything else in the truck is like-new, so considering what these trucks cost new, the money spent in doing the best job possible would seem to be more than worth the effort and expense. Just my thoughts...