The Plymouth Neon, built with a 2.0-liter or a 2.2-liter engine, proved to be popular with consumers for its fuel economy and stylish design. The engine, built by Mitsubishi, was generally very durable, with most of the no-start problems due to broken timing belts or engine sensor problems. At one time there was a technical bulletin issued by Chrysler with detailed instructions regarding cam sensor failures which could lead to a no-start condition. With a few checks, pinpointing the problem can be easy to do.
Remove the fuel pump relay located in the electrical service panel next to the battery. Remove the air inlet tube at the throttle body. Open the throttle body and spray aerosol start fluid into the opening. Crank the engine over. If it starts, the problem is in the fuel pump circuit. Check the fuel pump fuse, relay and fuel filter. Usually the problem is a defective fuel pump. Remove the pump from the tank and replace it.
Check the spark. Remove a spark plug wire and insert a spark plug. Lay the plug on engine metal so it will ground. Have an assistant crank the engine and observe the plug. It should spark as the engine is cranked over. If not, the problem is likely a cam sensor or crankshaft sensor. The car's computer must know the right timing to send to the spark. If the sensors are not communicating with the computer, the engine cannot send fuel injection signals or spark signals. Check the cam sensor carefully and inspect the wiring. Install an updated cam sensor if necessary and repair the wiring connector.
Inspect the timing belt by removing the upper timing belt cover. A stripped timing belt is usually obvious to detect by the missing belt cogs or frayed belt material. At times the belt may appear intact, but rotating the engine will reveal that a few cogs of the belt have sheared off. The engine will not run because the valves are not operating in sync with the pistons. Replace the belt to get the engine running again.
Check the exhaust for a restricted catalytic converter. If everything is testing fine and the car won't start, it could be a restricted or blocked exhaust system. Loosen the main exhaust pipe that connects to the exhaust manifold. This will free the exhaust flow. Crank the car and see if it starts. If it does start, the engine will be loud as the exhaust bypasses the converter and muffler. Replace the converter to finish the repair.
