One downside to all diesel powered vehicles, including any using GM's 6.5-liter engine, is that diesel fuel gels at higher temperatures than gasoline, thus making cold-weather starts more difficult. This means that if you are operating your diesel in extreme cold weather, you must add supplemental warming equipment to ensure your truck starts, while taking extra time to allow the engine glow plugs to assist in startup.
Making sure your glow plugs are functioning is the most important thing you can do to ensure your truck will start in subzero temperatures. Diesel engines are equipped with glow plugs that warm the air inside the combustion chamber. Because diesels operate by pressure, heating the combustion chamber air via glow plugs is how the 6.5-liter achieves cold-weather starts.
It is common on an older vehicle, particularly one that sees salty winters, to have either the glow plug wires, or one or more glow plugs die. The glow plugs are installed in the engine head right near the injector, and held in place with a 10 mm bolt.
Allow the warmup procedure to complete before cranking the engine. Wait for the glow plug light to extinguish, then crank the engine for three to five seconds. If the engine fails to start, you may also want to cycle your glow plugs a second time to ensure complete heating of the combustion chamber. Once the vehicle starts, make sure you are gentle on the engine until it reaches normal operating temperatures. The 6.5 turbodiesel recycles fuel through the fuel return line while running, so letting the truck idle for a few minutes before driving will warm the fuel in both the fuel tank and in the fuel lines.
Installing additional support hardware will make a dramatic difference in your 6.5's ability to start in extreme cold weather. If you don't have a block heater, then you should seriously consider installing either an aftermarket fluid-recirculation heater, or retrofit a heater from GM. While many 6.5-liters came equipped with a block heater from the factory, you can also add battery mats to warm the batteries and an oil pan blanket to warm the oil in the crankcase. You can run all three accessories to a common plug that you then connect to a outlet when your truck is parked.
A n overlooked aspect of starting up your 6.5 turbodiesel is the age of your batteries Batteries deteriorate over time and perform weakly in cold weather. By making sure your 6.5 equipped truck has two fresh batteries, you can be assured that maximum charge is available to the starter.
You can add special additives to diesel fuel to prevent crystallizing and gelling, which will allow for starting in extreme temperatures, and a diesel operating in subzero temperatures should be regularly treated to ensure that the diesel fuel in the lines and tank does not gel or collect crystals. Note that because the 6.5 turbodiesel uses an optical sensor on the injection pump, you want to avoid dark colored additives, as well as those that have excessive detergent or alcohol content. A popular clear colored additive for the 6.5 turbodiesel is Standyne performance formula.
High-quality synthetic oils greatly assist starting and running of the 6.5 turbodiesel. Swapping from 15W-40 oils to a full synthetic 5W-40 allows for a thinner oil which maintains its properties at low temperatures.
