Diesel semis are powerful and efficient trucks, but engine troubles are still possible. The most likely culprit for a poorly running semi is sludgy diesel fuel. This problem begins in the fuel tank, which makes cleaning it regularly necessary.
Diesel Degrades To Solids
Diesel is a great fuel because it is efficient, but it will slowly start to degrade into sludge. Generally speaking, it takes about 60 to 90 days for diesel to reach this state. While this should be more than enough for you to burn through most of the diesel in your truck, there's a chance that some residue remains.
Unfortunately, this means that sludgy diesel fuel may be slowly building up in your engine. This will decrease your engine's efficiency (by making it harder to process the thicker fuel residue) and can damage the interior of your engine. This may cause your engine to fail completely.
Knowing When To Clean Your Tank
The easiest way of gauging your fuel is to take a diesel sample from your truck's tank using a fuel sampler kit. This kit includes a hose which you snake into the bottom of your tank. The other end of the hose is attached to a small bottle with a hand pump.
Once the hose is in the bottom of the tank, pump out a sample of fuel and visually inspect it. You are going to want to get fuel from the bottom of the tank, as this is where the thickest and sludgiest diesel will be resting.
Cleaning A Diesel Tank
If you see any sludgy fuel, it is time to clean your fuel tank.. Start by putting on goggles, elbow-length rubber gloves, and a rubber apron. Now crawl under your truck, locate the tank (under the front of the truck) and place a large diesel container (larger than your tank's full capacity) under the drain hole of the tank.
Open the drain hole and let the fuel drain out into the pan. Once the flow of fuel has stopped, close the drain tank and carefully remove the nuts holding the tank to your engine. The location and type of these will vary depending on your truck, so make sure to bring a full wrench kit to the job.
After removing the tank, take it to an open area of your yard and place it on top of a small tarp. Place the tank with the sealed drain hole down and fill the tank with a diesel tank cleaner (with an ultra-low sulfur content) from the pipe that connects it to the engine. Let the solution soak for at least half an hour before dumping it into a sealing bucket.
Let your tank dry for another half an hour and then reattach it to the engine. Make sure to double-check the pipe connection to ensure that it is as tight as possible. Pour the sludgy diesel into another sealing bucket. Refill your engine with new diesel fuel.
After finishing up, take a trip to your local diesel depot, like http://unitedoil.net. Here you can dispose of your waste buckets and have a mechanic run an engine cleaner through your truck to break up any sludgy fuel remnants.