Add to this the legendary behind your Duramax, built on the expertise that has come with decades of heavy-duty commercial and military tactical vehicle transmissions, and its easy to see that the potential longevity of your Duramax/Allison combo is one of the highest quality powertrains in the light/heavy duty truck market.
Diagnosing an injector failure on a Duramax is fairly straight forward but requires some special tools and service information. we have had our fair share of LB7/Early LLY trucks in the shop which were smoking but the balance or return rate data was within spec, so they were denied coverage under the special GM policy which covers them for 7 years/200k miles. I'm not sure what the options are at that point other than to just replace them out of pocket. which is very expensive.
There are however some things you can do to help minimize injector issues.
*change your fuel filter regularly*
*use a fuel conditioner/lubricity enhancer*
*do not use dirty fuel, or fuel from low volume stations*
* If you have considered a tuner or are running a tuner, it would be a good idea to install a fuel lift pump system, the stock system must rely on the lift pump incorporated into the injection pump, and must pull fuel from the tank. on the LBZ,LMM, it is very easy to run the fuel system "dry" under load meaning, the pump and injectors will suffer from a lack of fuel. this will cause damage to either component in a very short period of time.
To understand injector failures, you must first understand how the fuel system on a duramax diesel works.
Fuel is drawn out of the tank via a tandem high pressure pump which is driven off of the camshaft gear on the front of the engine. it then enters the high pressure portion of the pump where it is regulated and pressurized depending on desired power output, excess fuel is returned to the fuel tank at the injector. there is a fuel pressure sensor on the high pressure side of the system, mounted in the fuel rail assembley. this sensor sends an electrical signal back to the ECM based on pressure. there is also a pressure relief in the high pressure fuel system. this valve is a mechanical device which when maximum fuel rail pressures are exceeded, will open and release this pressure returning it back to the fuel tank passing first through a fluid to air cooler.
What Goes Wrong?
A stock LB7 will at some point, or has at some point, need a set of injectors. these early injectors are a very poor design, and have suffered a high failure rate. they were supposedly re-designed, but we still see about the same amount of failure. One of the reasons for failure is that these injectors require a higher operating voltage than the later injection systems. the electrical section runs hotter and is more likely to have failure.
There was plenty of excitement when GM stepped up and extended the injector warranty under a special policy to replace failed injectors. this policy covers injectors for seven years, 200,000 miles. the rules have recently changed. the problem with this policy is that injector failures must meet certain criteria in order to qualify for covered replacement.
A good example of this would be if your Duramax LB7 is smoking, and all other fuel system components check out, yet the injector balance rates are within the specification, you will not get injector coverage. you are now faced with a four to five thousand dollar repair.
Proper maintenence can help minimize injector failures as well as alcohol free, lubricity enhancing fuel additives.
Update: most all of the LB7 trucks are past the time limit for injector warranty replacement.
The 04.5-06 LLY
The LLY was an improvement over the LB7 both in power output and reliability. with a VGT turbo and an EGR/DOC system it was also quite a bit cleaner.
One problem we have seen on the LLY concernes the head gaskets. the early head gaskets are a multi layer steel design. they are crimped around the edges and fully crimped around the cylinder sealing area or fire ring. the later gasket does not have crimps, it is made up of stacked layers which are rivited in two places to hold them together.
Under certain load and fueling conditions, the early crimped gaskets can fail around the fire ring and allow combustion pressure into the cooling system causing overheating and coolant loss. the reason these gaskets fail is due to localized heat in the combustion chamber. this heat will burn the thin material which seals the combustion chamber causing a combustion leak. there have also been cases where a piece if this material will fall off into the chamber.
Head studs are overkill on the Dmax. unless you are going to do some serious competition. there are eighteen head bolts, and with a new gasket and a cylinder head which is flat and clean, new bolts and gaskets are adequet for longevity.
The 06-07 LBZ
The LBZ was a definite home run for DMax Ltd. When stock, they have a limited amount of failures mostly related to fuel rail pressure loss due to fuel supply deficiencies-Fuel filter restrictions, and fuel rail pressure relief failure.
This system has many safegaurds built in, if you are limping the engine or transmission, the system is trying to tell you something is either slipping or starving, using a band aid fix to mask these issues will only delay catastrophy. aftermarket tuning devices can actually enhance fuel economy, but can also cause damage to the engine and transmission.
The Allison control system has built in safeguards. if you plan on running a tuner, you will at some point experience reduced power mode. this happens when the TCM detects slippage, overheating or any electronic fault.
Once again another home run hit? well, almost. with the addition of a DPF, comes more issues. one issue is of course the introdution of an injection event during the exhaust stroke to light off the DPF during a regeneration cycle. this can cause fuel to make its way to the engines crankcase, and delute the oil making shorter oil change intervals a very good idea.
As this plaform ages, we will see more emerging issues directly related to the DPF.
And as always, you can be sure we will stay ahead of these issues with training and tooling to support our customers who own a Duramax.
This platform is the culmination of several years of diesel emission systems test and design. It is much more powerful and cleaner than previous Duramax engines. with the use of diesel exhaust fluid, I expect to see a significant reduction in DPF related failures/issues. We expect to see reliability as good or better than the LBZ.
If you have any questions concerning your duramax/allison, give us a call today
Fleet Service Northwest 503-982-5516