How to Troubleshoot a 318 Mopar

by Sam Jenkins

Mopar's 318 engine is one of the most durable and longest-produced V8 engines in the automotive industry. This motor was in production from 1967 to 2002, and found as an option for nearly every Chrysler vehicle available with a V8, from Plymouth Barracudas and Chrysler Cordobas to Dodge Ram pickup trucks and buses. Like any engine, the 318 can start to run a little rough after a few years. Fortunately, this engine is easy to troubleshoot.

Set Your Timing

Unplug the vacuum advance hose on your distributor and plug it up with a small bolt.

Loosen your distributor clamp. This requires a 1/2-inch wrench. Don't loosen the clamp too much. Just loosen it enough to be able to rotate the distributor and feel a little resistance.

Attach your timing light leads. The black lead goes to the negative pole on your battery, and the red goes to the positive pole. The third lead clamps around your No. 1 spark plug wire. This is the front-most plug wire on the passenger side of the engine.

Start your engine.

Shine your timing light on the harmonic balancer from the passenger side of the motor.

Rotate your distributor until the timing mark on your engine lines up with the 10 BTDC mark on the timing cover of the engine.

Tighten down the distributor and reattach the vacuum hose. Reset your idle speed if necessary.

Air and Fuel

Adjust your idle mixture screw(s) if your 318 is equipped with a carburetor. Since the 318 had such a long production run, it has been available with a number of different carburetors. Usually the idle mixture screw(s) are located at the front of the carburetor. Turn each screw in and out a half a turn at a time with the engine running until you achieve the highest rpm. If your carburetor has more than one mixture screw, be sure both screws are turned out the same number of turns.

Rebuild your carburetor if necessary. If you have set both your timing and idle mixture and your 318 still runs rough, it would probably be worth it to rebuild the carburetor. You can purchase a kit at your local auto parts store.

Replace your air filter.

Check for vacuum leaks if your 318 still runs rough. Take some WD-40 and spray around the base of the carburetor and outside edges of the intake manifold. If your RPMs increase, you have a vacuum leak and may need a new carb gasket or intake gaskets.

Other Steps to Take

Check your PCV valve. Remove the PCV from the valve cover and shake it. If a rattling noise is present, your PCV is fine. If no noise happens when you shake it, it's time for a new PCV valve.

Replace your spark plugs. Gap each new plug at .035 inches.

Check to see if your engine still runs rough after tasking these steps. If so, your 318 might have internal damage, possibly to the camshaft lobes or other rotating assembles. Take the vehicle to a professional mechanic.

Items you will need

About the Author

Sam Jenkins has been a professional writer since 2008 with his contributions to the award-winning "Guilfordian" newspaper. He has a Bachelor of Arts in English with a minor in communications which he received in 2010 from Guilford College.

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