An engine backfire happens when fuel emerges from the engine, and bursts into flame. If you have this problem with your truck engine, or you find that it sputters or fires fuel into the air, then you may have to troubleshoot the engine in order to work out the cause of your backfire. There are a few reasons why this could be happening, from the most complicated - that is it has a faulty connection somewhere in the electrical system, to the very simple - such as the presence of water in the fuel tank. In order to work out which of these problems you have, you will need to do some troubleshooting. This can be done by a professional, who will have the tools to troubleshoot your engine backfire, or you can try to do some simple repairs yourself.
Check the Fuel Tank
You should check the fuel tank on your truck, and make sure that there is no water in the system. Garages often keep a machine which detects water in the fuel tank, but another solution is to remove the tank from its location, empty the fuel inside, and then leave it to dry in a warm, moisture-free place for around a week. Check that there is no liquid in the tank before you replace it. Fill up the tank again, and try running it from this position.
Check the Spark Plugs
Your spark plugs should be checked next. These can become worn, or may shift out of true, and the small electrical charge they carry can't be enough to ignite any gas leaving for the tailpipe. Remove your spark plugs and replace them; testing them can be more time consuming and costly than just putting new ones in. Check your car again.
Check the Valves
Another cause of engine backfire can be carburettor valves. These can sometimes become sticky with grease, meaning they don't close up properly. A number of chemicals and products can be purchased from car supply stores to deal with this problem. Simply pour the liquid into your carburettor or the gas tank, and run the car again. This is not a fix so much as a temporary solution, and you will need to rebuild the valve heads in order to get it working properly again.
You can also get truck engine backfire from loose connections in the engine itself. Like the spark plugs, electrical connections can work their way free and create enough charge to cause the engine to backfire into itself. Look at the connections, and if there are any that are corroded, loose, or have damaged insulation, remove these and resolder some new wire into the engine. You should try running the car after each fix to see whether one wire was the cause of the problems. The engine itself can also become charged with static electricity, but if this happens on a regular basis, you will need to call in a mechanic to get the problem fixed by a professional.