Chevy Silverado/GMC Sierra Duramax

In 2001, GM released the all-new Duramax 6.6L V8 turbo diesel engine in the Silverado and Sierra HD pickups. Each individual version of the Duramax in identified by the Regular Production Option (RPO) code. The first version in 2001 was RPO code LB7, followed by the LLY, LBZ, LMM, LML, and, most recently, the L5P.

Luke’s Auto Repair and Diesel offers a wide variety of maintenance services for these pickups, such as fuel filters and air filters, and many repair services, such as EGR valves and glow plugs. Whether you need injectors replaced, or a check engine light diagnosed, we are here for you.

If you are looking for better reliability, fuel mileage, or performance from your Duramax truck, Luke’s Auto Repair and Diesel is here to help. We offer performance lift pump systems to keep your fuel system clean and well supplied, and stud kits to prevent head gaskets from blowing. If you’re looking for a simple tuner or cold air intake, or a major upgrade, such as a performance turbo, over-stock injectors, or a stroker injection pump, we are your source.

All Duramax HD pickups are equipped with the Allison transmission. We offer fluid and filter changes for Allisons as a routine maintenance service. Older trucks need to be serviced every 25,000 miles, newer trucks every 45,000 miles. We also offer performance upgrades for the Allison, such as deep sump pans and transmission tuning.

Chevy Colorado/GMC Canyon Duramax

A Duramax engine is also offered in the Chevy Colorado/GMC Canyon midsized pickup as a 2.8L 4-cylinder, RPO LWN, starting in the 2016 model year. A combination of good power and excellent fuel economy make this option stand out in the midsize pickup market. Luke’s Auto Repair and Diesel offers standard maintenance and repair services for Colorado and Canyon. Whether you need a simple fuel filter change or a complete timing belt replacement, we can help.

We also offer performance upgrades for these trucks. If you’re looking for an engine or transmission tuner, a cold air intake, or a custom upgrade, we are your source.

Chevy Express/GMC Savanna Duramax

The Duramax is available in the Chevy Express/GMC Savanna full-size vans. Some versions use a 6.6L V8, similar to the HD pickups. Other vans use the 2.8L 4-cylinder, similar to the Colorado. These vans can be an excellent fit for a person that tows and hauls substantial loads.

Luke’s Auto Repair and Diesel offers maintenance services for these vans, such as air filters, fuel filters, and transmission services, and a wide variety of repairs, including EGR valves and glow plugs.

Whether you need the DEF system repaired, or a check engine light diagnosed, we are here to help.

Performance lift pump systems

Chevrolet Silverado/GMC Sierra Duramax trucks do not have an electric lift pump from the factory (until the L5P was introduced in 2017). These engines rely on a mechanical low-pressure section of the injection pump to draw fuel from the tank up to the engine. Performance lift pump systems, such as those offered by AirDog or FASS, provide multiple benefits for your Duramax:

Prolongs the life of injection pumps

One of the more common failures of the CP3 injection pump used in earlier Duramax pickups is the low-pressure lift section that draws fuel from the tank to the engine. Adding a performance lift pump, and pushing fuel to the engine will put less stress on the injection pump and can lengthen its life.

Air separator and fuel filtration

AirDog and FASS systems include an air separator that prevents air from reaching the injection pump and injectors. The system is designed to compress fuel, not air. If air enters the injectors, it can end up “dry firing,” essentially slamming internal parts and shortening their life. These performance lift pump systems also include a high-quality fuel filtration system to remove contaminants before they enter the
pump and injectors.

High-capacity water separator

AirDog and FASS systems include a water separator with a much larger capacity than what the factory system is equipped with. Water is the single most destructive contaminant in diesel fuel. It reduces lubrication needed for injectors and injection pumps, leading to premature wear or damaged injector tips. It can cause internal rust in the fuel system, and freeze inside fuel lines during cold weather. Water also reduces the amount of usable energy in a gallon of diesel, resulting in reduced engine power output. Using a FASS or AirDog system gives you a much larger water-holding capacity, and helps keep the damage out of your fuel system.

Eliminates hand-priming the fuel system

Until the L5P, there was no electric lift pump on the Duramax pickups. If you’ve ever changed the fuel filter on your truck, you know that using the hand pump on top of the filter housing to prime the system can be a tiring and lengthy process. Performance lift pump systems make that a thing of the past. Simply cycle the key to run the electric pump.

Supports tuners and other modifications

AirDog and FASS systems provide extra fuel volume needed for modifications such as tuners, larger injection pumps, and performance injectors. They can help prevent the fuel rail from running dry and derating the engine.

Custom tuning

Luke’s Auto Repair and Diesel can work with custom tuning companies to provide you with a solution that’s right for your truck. Custom tuning provides several benefits that an off-the-shelf tuner cannot. Custom tunes can be written for your specific truck, with your specific modifications and needs in mind. An off-the-shelf tuner may not be able to accurately compensate for performance upgrades, such as high-flow intake components or bigger injectors. Using an off-the-shelf tuner with other performance parts may result in a smokey or rough running engine, or in a worst case scenario, engine damage under heavy loads. Custom tuning is also available for Allison transmissions. Transmission tuning is highly recommended for any Duramax truck that has performance engine modifications.

Please call or use the contact form if you have questions about custom tuning for your truck.

LML CP3 conversion

The LML Duramax uses the Bosch CP4 injection pump. This pump can have internal problems, often due to poor fuel quality. When it fails, it sends tiny metal particles through the high-pressure fuel system, including the injectors and fuel rails. Replacing eight injectors and the CP4, with associated parts and labor, can top $9,000 or more.

One solution to this issue is to retrofit the LML with the Bosch CP3 injection pump used in earlier versions of the Duramax. The CP3 is a more robust pump that also has a greater fuel pumping capacity. Stock sized and performance pumps are available. The conversion can be performed proactively, as a preventative measure, or as part of the repair after a CP4 failure. Please call or use the contact form if you have questions about a CP3 conversion for your LML.

Diesel Particulate Filter (DPF)

What is a DPF?

Most Duramax trucks and vans in the 2008 model year and newer are equipped with a DPF. The DPF is an emissions control device located in the diesel exhaust system that traps particulate matter created during engine operation. Periodically, the DPF must go through a regeneration, or “regen,” process to burn off the particulates. This requires that exhaust temperatures be very high, often above 1,000 degrees Fahrenheit.

What is required for a regen event to happen?

Temperature is one of the biggest factors. The engine control system must be able to get the exhaust temperatures high enough to begin a regen event. Trucks that make frequent short trips often cannot achieve the proper thresholds. Driving your Duramax on the highway for at least 30 minutes will often allow the system to initiate a regen.

What happens when a DPF malfunctions?

If the truck cannot complete a regen cycle, or cannot regen often enough, the DPF may begin to fill up and become a restriction in the exhaust system. An improper air/fuel ratio created by a weak turbo, stuck EGR valve, or the wrong tuning can also cause the DPF to fill up quickly. When this happens, the check engine light may come on, and the driver will often see warning messages, such as “Service Particulate Filter System.” If the condition continues, the control system may limit vehicle speed and power.

How do I fix a clogged DPF?

If you are seeing warning messages related to the DPF, or have engine trouble codes related to the DPF, please bring your Duramax in for service as soon as possible. If the problem is addressed early on, it is often less expensive to fix. Sometimes the problem can be addressed using a professional scan tool to force a regen. General engine control issues, such as turbo and EGR problems, can also cause the DPF to clog prematurely. Malfunctioning exhaust sensors can also cause some of the conditions mentioned above, so accurate diagnostics are important to ensure the problem is solved correctly. Complete DPF replacement may be needed in some instances. Luke’s Auto Repair and Diesel offers a full range of diagnostics and repair services for the DPF system on your Duramax truck.

Do I need to delete the DPF if I want more power from my Duramax? No. It is possible to make substantial power gains over stock with the emissions system fully intact using the proper tuning and modifications. A DPF in good condition offers little restriction to the exhaust.

Diesel Exhaust Fluid (DEF)

What is DEF?

Most Duramax trucks and vans in the 2011 model year and newer are equipped with an on-board DEF system. DEF is a liquid injected into the exhaust to cause a chemical reaction and aid in emissions compliance. There is a tank mounted in the truck that must be filled periodically. The system includes a pump, level sensor, and heater in the tank, with a line leading to an electronically controlled injector mounted in the exhaust.

What is a DEF heater? 

DEF will freeze at approximately 12 degrees Fahrenheit, so the tank contains a heater to ensure proper operation in cold temperatures. The heater is managed and monitored by the engine control system.

What happens when the DEF system malfunctions? 

When the engine control system detects a fault with the DEF system, it will often turn on the check engine light and/or display a warning message, such as “Service Exhaust Fluid System.” Failures can range from failed DEF heaters to clogged DEF injectors. Luke’s Auto Repair and Diesel offers a full range of diagnostics and repair services for the DEF system on your Duramax truck.