Chevrolet Silverado: 6.6 Duramax LB7 injector failure (fuel in oil, hard hot start, smoke)
6.6 Duramax LB7 injector failure (fuel in oil, hard hot start, smoke) is a very common engine fault on the Chevrolet Silverado on the 2001–2004 cars, and we rate it critical. Putting it right costs $6,000 to $11,000 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 14 documented faults on the Chevrolet Silverado.
- Vehicle
- Chevrolet Silverado
- Engine
- 6.6L
- Years
- 2001–2004
- Fuel
- diesel
- System
- Engine
What you are looking at
Example of the part — not this vehicleA common-rail diesel injector. Contamination damages the nozzle at the tip.
What goes wrong
The first Duramax diesel, the LB7 fitted to 2001-2004 2500HD trucks, is notorious for injector failure: injector bodies crack and dump diesel into the sump, or leak back to the tank so the engine is hard to start when hot, and worn injectors cause white or black smoke and a rough idle. Failures were so common that GM extended injector warranty to 7 years / 200,000 miles, which has now expired everywhere. Diesel diluting the engine oil is the dangerous version, because it thins the oil and can wipe out bearings. The injectors sit under the valve covers, so replacement is a big job, usually done as a full set of eight.
What you would notice
- Engine oil level rising on the dipstick or oil smelling of diesel
- Long crank before starting when the engine is hot
- White or black smoke at idle or under load
- Rough idle, misfire or knocking
- Fuel economy getting worse
How to check it
Where to look. Fuel injectors under both valve covers on the 6.6 Duramax LB7
Check the dipstick: oil that is above the full mark, thin, or smells of diesel means an injector is leaking into the sump.
Ask to start the truck from cold, then again after the test drive when hot; a hot engine that cranks for several seconds before firing points to a leaking injector.
Watch the exhaust at idle and during a firm acceleration for heavy white or black smoke, and listen for a rough idle or a knock.
Ask for proof of injector replacement, including the date, kilometres and whether all eight were done.
If a workshop inspection is possible: a diesel specialist can run injector balance rates on a scan tool and do a return-flow test to find leaking injectors.
What it costs to put right
$6,000 to $11,000 at New Zealand independent workshop rates. That is for this job on its own, not for the car.
Ask the seller
- “Have the injectors been replaced, when, and were all eight done?”
- “Does the oil level ever rise between changes?”
- “Does it start easily when hot?”
Now check the Chevrolet Silverado you are actually looking at
Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.
Where this comes from
- Engine Builder Magazine 'Venturing Into GM Duramax Diesel Service' (LB7 injector warranty extension to 7 years / 200,000 miles)
- Diesel World 'Don't Lose Your Heads' (LB7 injector cracking and fuel dilution)
- Diesel Power Products blog 'What breaks when: LB7 Duramax'
Chevrolet Silverado buyer questions
Is 6.6 duramax lb7 injector failure (fuel in oil, hard hot start, smoke) serious on a Chevrolet Silverado?
We rate it critical and very common on the Chevrolet Silverado. The first Duramax diesel, the LB7 fitted to 2001-2004 2500HD trucks, is notorious for injector failure: injector bodies crack and dump diesel into the sump, or leak back to the tank so the engine is hard to start when hot, and worn injectors cause white or black smoke and a rough idle. Failures were so common that GM extended injector warranty to 7 years / 200,000 miles, which has now expired everywhere. Diesel diluting the engine oil is the dangerous version, because it thins the oil and can wipe out bearings. The injectors sit under the valve covers, so replacement is a big job, usually done as a full set of eight.
How much does it cost to fix on a Chevrolet Silverado?
$6,000 to $11,000 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.
Which Chevrolet Silverado years are affected?
Our research records this fault on the 2001–2004 Chevrolet Silverado. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.
How do I check for it before I buy?
Check the dipstick: oil that is above the full mark, thin, or smells of diesel means an injector is leaking into the sump. Ask to start the truck from cold, then again after the test drive when hot; a hot engine that cranks for several seconds before firing points to a leaking injector. Watch the exhaust at idle and during a firm acceleration for heavy white or black smoke, and listen for a rough idle or a knock. Ask for proof of injector replacement, including the date, kilometres and whether all eight were done. If a workshop inspection is possible: a diesel specialist can run injector balance rates on a scan tool and do a return-flow test to find leaking injectors. Look here: Fuel injectors under both valve covers on the 6.6 Duramax LB7