When the Duramax LB7 first hit the streets in 2001 it was a vast improvement over the Detroit Diesel it replaced. By the time the last LB7 rolled off the production line in 2004, it was putting down more power than anything Dodge or Ford had to offer at the time. In addition, it was the first diesel engine used in a light truck that employed a high-pressure common rail injection system.
While the Duramax has undergone several revisions since then, there are still many LB7’s on the road today due to their reliability and simplicity. Not to mention, it came before the stricter emissions standards that caused their own problems. However, the LB7 Duramax had one notable flaw, less than reliable fuel injectors. Due to a poor design, they were notorious for failing with less than 50,000 miles on them, causing GM to warranty the injectors for up to seven years/200,000 miles.
With that said, we’ll dive in and cover why they were so troublesome along with an excellent solution in the name of the SAC00.
What Does A Fuel Injector Do On A LB7?
In simple terms, the common rail injectors used in the LB7 and later Duramax diesels are similar in how they operate. They are a Bosch design that delivers fuel to each cylinder at a pressure ranging between 20,000 to 30,000 psi depending on the year and model of the engine.
With that said, the LB7 used a valve covering orifice (VCO) injector whereas the LLY and later utilized a SAC-style and we will cover the differences between them.
VCO and SAC Injectors
Without getting overly technical, it has to do with the pin inside the injector (the part that regulates the fuel flow). Depending on the year, they will have between five to seven holes where the fuel is sprayed into the cylinder. In the VCO design, the needle plugs the tip of the injector where holes are located. This is in contrast to a SAC style where the fuel is blocked upstream (before the holes).
The Problem with the VCO Injectors
While VCO injectors are quieter at idle and some claim they are better suited for high-horsepower applications, in Duramax terms they were troublesome to say the least. Simply put, they had tight tolerances and the needle was prone to wearing out. Making matters worse is the fact it has to plug each hole individually, thus creating more opportunities for a fuel leak. Lastly, the injector housing was prone to cracking although this was a separate issue.
All said and done, the injectors were prone to failing even in low mileage applications although things like not changing your fuel filter regularly or dirty fuel made it more likely.
What Are Common Fuel Injection Issues?
Chances are that most of the LB7 Duramax’s on the road today have had the injectors replaced by now. However, many times owners only replaced the ones that were bad or used cheaper aftermarket units. Unless you purchased the truck new or have the service history it may only be a matter of time before they need to be replaced again.
For the most part, a bad injector manifests itself in the form of excess fuel leaking into the cylinder, and below are some signs that one or more are on their way out.
- Rough idle and poor fuel economy.
- Excessive or constant smoke coming from the exhaust.
- Fuel in the engine oil.
- Difficult to start.
Of course, the extent of these problems will vary depending on the severity of the leak and how many injectors are affected. Many times, a minor leak will go unnoticed unless you perform a diagnostic on the fuel system. However, the most common symptoms are a combination of hard starting, reduced fuel economy, poor drivability, and excessive or constant smoke coming from the exhaust.
Likewise, another sign of a bad injector is the presence of fuel in engine oil. This is due to the fuel working its way down into the crankcase where it can dilute the oil and if left unchecked it can lead to excessive engine wear.
Suffice to say, if you still have the original injectors (or are unsure if they have been replaced) you should be aware of the above-mentioned symptoms and have the fuel system checked immediately should they appear.
Why Is A SAC00 Injector Superior To Stock?
Well, even GM acknowledged the VCO injectors were a problem on the LB7 Duramax and offered an extended warranty for affected owners. Likewise, they switched to a SAC-style injector on the LLY and haven’t looked back since.
It goes without saying that reliability and longevity were the name of the game and the SAC00 injector addressed that problem. Gone are the days of wondering which injector will fail and when along with the stress (and expense) of having to replace them. If you are experiencing any of the above-mentioned problems and a diagnosis confirms that one or more of your injectors are on the way out it might be time to consider a set of SAC00 injectors.
Why the SAC00 injector?
While there are cheaper options available, there is only one SAC00. In addition, they were developed in collaboration with Bosch (the original equipment manufacturer) to not only meet factory standards but exceed them. Keeping that in mind, the SAC00 is a drop-in replacement for stock and mildly tuned engines. As in, they have the same flow rate as the original units with no tuning or calibration required. Lastly, they are 50-state emissions legal and CARB-compliant.
While the SAC00 injectors are more expensive than some of the alternatives, they are vastly superior in terms of durability and longevity. In fact, they will likely be the last injectors you will ever need with that extra money being well spent and this is why many LB7 owners use SAC00 injectors in their trucks today.
How Tough Is It To Install SAC00 Injectors?
Suffice to say, replacing the injectors on an LB7 Duramax is a time-consuming task, albeit not impossible for a more experienced home mechanic. However, if this is your first time doing it you can expect to spend the entire weekend as the SAC00 injectors need to be installed as a set of eight.
In overly simplified terms, it is more tedious than difficult. Making matters worse is the fact the injectors on the LB7 are located under the valve cover. Getting to them means having to remove things like the air intake and turbo piping, fuel lines, wiring harnesses, and valve covers. After that, there are a few more bolts and connectors holding them in place. Likewise, it requires some extra patience to carefully remove them as the injectors tend to be stuck in place. Not to mention, making sure no dirt or sludge falls into the holes.
As for installation, you will need to replace the injector seals and O-rings, valve cover gasket, and possibly the fuel lines to name a few. Then of course add in any other worn-out components like hoses, connectors, or clamps that may break or are due to be replaced. Suffice to say, it is not a fun job and you will probably only want to do it once.
Alternatively, (and if DIY is not your thing) you can opt to have them installed at your local repair shop. Labor rates will vary by location, but all said and done it is about 10 to 12 hours of shop time and in most cases will add up to $1,000 or more.
Where Can You Get SAC00 Injectors?
At Merchant Automotive we know two things, Duramax engines, and Allison transmissions.
From LB7’s to L5P Duramax, we are your go-to source for everything related to GM diesels (including the LWN Canyon and Colorado). When it comes to keeping your LB7 on the road and replacing those troublesome injectors with a set of SAC00’s, Merchant has you covered. Likewise, we stock all of the extra items like gaskets, filters, and seals that you will need to get the job done right the first time.
We also operate a full-service shop that is staffed by ASE-certified diesel technicians and offer a range of services from routine maintenance, pre-purchase inspections, and SAC00 injector installs.
We help you get it done!
