Causes of Backfiring in Diesel Trucks


The sound of a vehicle backfiring can be startling, especially if that vehicle is a diesel truck. Backfiring is not only annoying, but it can be an indication of a more serious problem with the truck's engine or fuel system. Simply ignoring the backfiring can further complicate the existing problem, so backfiring should be addressed as quickly as possible.


  • The presence of water in your fuel system can cause backfiring while driving. If you do not have the time or expertise to look in your truck's fuel tank, mechanics have a device that can detect water in a gas tank. If you want to fix the problem yourself, you will need to remove the fuel tank. After the tank is removed, drain any diesel left inside, then set the fuel tank aside to dry for several days. Before reinstalling the fuel tank, make sure it is completely dry inside, then put diesel back into the tank and reinstall it onto the truck.

Spark Plugs

  • A simpler problem to check and correct is the spark plugs. A worn out spark plug can burn any leftover diesel fuel exiting the engine and entering the exhaust system of the truck, causing backfires. The quickest way to test the spark plugs is to simply buy new plugs and install them in your truck's engine. If the backfiring continues, then you know the spark plugs are not the culprit.

Loose Connections

  • Electrical connections in a diesel engine can become loose, worn out or corroded. Loose electrical connections can be the cause of backfires. A close inspection of the engine can turn up worn out or corroded electrical connections that are possibly the cause of backfires. After you repair loose connections and replace corroded wires, run the engine to see if the backfires continue. If they do, the cause of backfiring may be that the entire diesel engine is charged with static electricity. If this is the case, the problem needs to be turned over to a professional mechanic.


  • Buildup on valves can cause them to operate incorrectly so that your truck's valves remain open when they are supposed to be closed. Automotive supply stores sell a number of additives that can be poured into the truck's fuel system or engine to clean deposits off the valves. If the problem is advanced, a rebuild of the truck's valve heads may be in order.

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