Another symptom of cracked injector failure would be fuel dilution in the engine oil. This would come from the injector’s body being cracked externally, causing fuel to leak into the crankcase.
You have to remember that the injectors of the LB7 were under the valve cover. The hard lines come from the high-pressure fuel rail and went through the valve cover.
So if the injectors were leaking externally, fuel dilution could happen fairly quickly and go unnoticed because the engine would operate fine.
There have been some injectors leaking externally so badly that the crankcase had filled with so much diesel that it was coming from the rear main seal.
The particular truck I was working on with this condition was dripping diesel fuel from the rear main seal without the engine even running in the parking lot.
The last form of injector failure was a hard start condition when the engine was hot.
When the engine was cold, the vehicle would start fine and drive normally without any noticeable problems until the owner decided to stop somewhere like the store to get some fuel.
When the owner would try to start the vehicle, the engine would spin over but never fire.
The injector’s body was cracked on the return side, causing the fuel pressure that was entering the injector to be returned to the fuel tank.
The vehicle would literally have to sit for several hours and cool down before the engine would restart. The heat from the engine would cause the crack in the injector body to expand open.
That’s why the engine will start fine when cold and struggle to crank when warm.
With so many injector failures between 2001 and 2004, GM extended the injectors’ warranty from five years/100,000 miles to seven years/200,000 miles. This did not, however, remedy the problem. Bosch went through several designs before there seemed to be a cure.
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The biggest problem came when customers had their injectors replaced under the seven-year/200,000-mile warranty.
Then several years later, after the truck was out of warranty, the injectors failed again.
This of course angered many customers because there was still a problem and now they were going to have to pay for it.
But, if the other injectors didn’t last very long, this would be an ongoing problem for the owner.
The injector replacement in the LB7 Duramax is labor intensive.
With the injectors being under the valve cover, a lot of the components of the top of the engine have to be removed in order to access them.
It’s always advised that if there are several injectors causing problems that it’s better to replace them all because of the amount of labor that it takes to get to the injector.
The average cost of an injector replacement on the LB7 is generally around $4,000 to $5,000. The replacement process takes between 10 to 12 hours of labor and the injectors cost around $350 each.
In the middle of 2004, GM released the second generation of the Duramax, with the RPO code of LLY, with the eighth digit of the VIN designated as number 2.
The LLY was in production from 2004.5 to 2006, and was made with 310 hp and 605 ft.-lbs. of torque.
There were several reasons for the change: the injectors changed design and were now on the outside of the valve covers, providing easier access, and the EPA was tightening down on emissions standards for diesel engines in order to reduce NOx gas.
