Your Duramax's injectors are worn out — a normal life event around 200,000 km on the LBZ, LMM and LML. We replace all eight, plus the cracking return lines, in one visit at your home.
Bosch common-rail injectors on the LBZ, LMM and LML Duramax are precision instruments — needle valves and nozzle holes machined to micron tolerances, firing multiple times per combustion event at enormous pressure. Around 200,000 km, that precision erodes. Nozzle holes wash out and spray patterns turn from a fine mist into streams; internal seats wear and injectors start dribbling fuel they should be sealing.
Worn injectors over-fuel and under-atomize at the same time: that's the black smoke under throttle, the diesel rattle at idle, and the misfire codes. The long cranks come from injectors bleeding rail pressure back into the return circuit while the engine is off — the pump has to rebuild pressure from scratch every start. Each injector wears differently, which is why the idle gets lumpy: eight cylinders, eight different fuel deliveries.
The return lines deserve their own mention because they're the cheap part that strands trucks. The rubber return hoses between injectors age, harden and micro-crack — and a cracked return line means air in the fuel system, hard starts, and diesel weeping into the engine valley. Replacing eight injectors without the few dollars of return harness is how this job comes back. We do them together, always.
If your GM is doing any of these, this is the likely cause:
Worn injectors don't just run badly — they wash cylinder walls with unburned fuel, dilute the engine oil, and in the worst case a dribbling injector can melt a piston crown. The long cranks also grind away at your starter and batteries all winter. Injectors at 200,000 km are a known service item; injectors at 250,000 km ignored are an engine-life gamble.
Yes — it's a long day of top-end work, but it's all engine-in-truck. We bring the injectors, seals, return harness, coding tool and filters, do the job on level ground, and road test it before we leave. No tow, no week in a shop bay.
Eight precision injectors are legitimately expensive parts, and the labour to reach them is many book hours — dealers bill both at full rate, and quotes often grow mid-job. We give you one flat price for the complete set, return lines, coding and filters before we start. The number you approve is the number you pay.
We can, but on a 200,000 km truck we'll talk you out of it: the other seven have identical wear, and you'll be paying the same big labour bill again within the year. One visit, eight injectors, done for the rest of your ownership — that's the math that actually works.
Because they're cheap, they're already brittle at this age, and a cracked one causes hard starts and fuel leaks that look exactly like a failed injector — after you've paid for injectors. Every credible Duramax injector job includes the return harness.
Send it over for a free second opinion. I'll tell you straight what the job actually involves — and if their quote is fair, I'll tell you that too.
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