Depending on what other maintenance is done at the same time as replacing 8 injectors on an LB7 Duramax, the overall cost may be between $4000 and $5000 CAD.     The price of the injector parts will be higher for larger vehicles with larger engines. Costs will be cheaper for smaller cars with smaller engines. The cost of the injector increases with the number of cylinders in your car's engine. The location and accessibility of the automobile type and injector line are likely to greatly impact the cost. Although labor is less expensive than replacing a complete injector, it can still be expensive for bigger GM vehicles.