To repair your 3.9-liter Dodge engine, first ascertain what the problem is. Common engine problems include wear to the hoses and engine belts, worn spark plugs and restricted air filters. Dodge offers free owner's manuals for models with 3.9-liter engines, including the Dakota, Charger and Challenger.
First, check the engine parts that commonly wear out or are easily damaged. Replace worn spark plugs. Check belts and hoses to make sure they are properly attached to the engine. A worn hose may bulge or have a spongy appearance. If there are cracks or splits in an engine hose, replace it with another that is recommended by the manufacturer for your vehicle model. Change air and oil filters routinely so that the engine can operate efficiently. A clean air filter also improves gas mileage, while the oil filter helps to keep the engine clean.
If the engine cranks slowly or does not start at all, check your car battery. Replace your battery every four years to ensure engine reliability. Test the battery by attaching it to a voltmeter. If the battery has less than 12.45 volts, charge it with a portable battery charger. Change the engine oil and add clean oil to improve engine performance.
Other reported problems with Dodge 3.9-liter engines include blown head gaskets, coolant leaks and faulty crank position sensor wire connectors. To solve ignition wiring problems, obtain a wiring diagram from the manufacturer. Use the diagram to identify the ignition wire under the dashboard, and replace or repair it accordingly. If the engine is overheating, the problem could be a blown head gasket. In this case, white smoke sometimes pours from the exhaust pipe. Check the oil. If it is light and creamy in color, the head gasket is damaged.