Duramax Engine Tips, Tricks, Failures and Fixes

Sep 14th 2020

Fuel Starvation Fuel Filter Housing

Duramax diesel engines are prone to fuel starvation, meaning they don't pump enough fuel and the leading cause for this is the Duramax engine does not have a lift pump to feed the injection pump. They utilize the factory gear pump on the back of the cp3, which then has to pull the fuel from the fuel tank through the fuel filter housing and filter to the front of the engine. Another factor for fuel starvation is the prone but common fuel lines. This is why installing an aftermarket fuel system like Fass is an excellent idea for someone looking to upgrade their truck. Another common issue is the fuel filter housing, the plunger pump on these have been well known for oring issues causing the engine to suck air and intrude air into the fuel system, which is never good for high-pressure fuel systems.

Water Pump Failure

Duramax has fewer issues with water pump failures since the earlier years. That's why we recommend replacing your coolant at 150,000 miles or every five years per GM recommendation. The cooling system is one of the most commonly overlooked systems on trucks today and has a major effect on your engine's lifespan.


Overheating is one of the lowest issues you should experience, but it is still higher than other engines. Summer months are more prone to have this issue arise, especially with pre-2006 models. 2006 and after, the engines have a larger radiator and fan to keep the engine cool. The fan clutch failing is usually the issue, but a clogged radiator can exacerbate the issue's likelihood. Grime will reduce the effectiveness of the heat exchanger/radiator. This why we recommend if you have any overheating issues to try cleaning your radiator first.

Injector Failure

The 2001 – 2004 models had the highest issues with this in the LB7 Duramax engines. Since the LB7, it has seemed that they have got the injector issues under control. Most replacement injectors have a 2-year unlimited mileage warranty on them now, which is nice. Consistent maintenance will also extend the life and decrease the likelihood of an issue arising, changing your fuel filter or even adding an aftermarket fuel system with a water separator/ fuel filter.

Injector Harness Chafing

Injector harness chafing is a long-term issue prone to happening and causes exposed wires, lack of power, and even a none start. The code will say it is an injector issue possibly related to an open circuit. One of the most overlooked things for injector harness is the harness pins. I have seen multiple trucks with the same injector replaced 2-5 times before making it's way to our shop. When I unplug the injector and do a pin drag test, and the test pin falls right in with no resistance, I can almost guarantee I have found the vehicle's injector problem.