Ford 4C3Z-12A342-AA Glow Plug

The glow plugs are designed for quick heating once voltage is applied; the end heat; the purpose of pre-chamber is to warm the air before compressing it. When fuel is being injected it is done under this heat causing it to ignite and in turn being forced into the cylinder for a second burn. To prevent the circuit from overheating, a cycling device is incorporated in the circuit. When a glow plug tip is missing or damaged it can mean incorrect fuel quality whereas, if the lip is distorted then it shows that the plug has been activated for longer than usual. The PCM controls the glow plug relay on-off times and consists of eight glow plugs, a relay, the PCM, an engine oil temperature sensor and a barometric pressure sensor controlling the glow duration with reference to oil temperature and barometric pressure respectively. In the instrument cluster, the WAIT TO START lamp lights up when the glow plugs are ready for the starting of the engine and lights up when the ignition is on and engine temperature is below 165 degrees F. The glow plug relay turns on the glow plugs and gets a signal from the PCM, and the type of relay system varies depending on the Federal or California standard vehicles. The federal models incorporate a single relay that is positioned close to the fuel filter, and the Californian models incorporate a glow plug module that is capable of monitoring the functions of individual glow plugs, although diagnostics of these are available only via the scan tool. The wiring harness of the car is equipped with two replaceable fusible links per glow plug bank. For replacement, the valve cover has to be pulled out to access the glow plugs, and these are removed and checked for damage before being reinstalled. Subject to 6.0L and 6.4L engines, there is a suggestion to use a special tool to dismantle the wiring from the glow plugs safely. The glow plug relay can be replaced by removing the negative battery terminal and electrical connectors, unscrewing the nuts of the relay then reinstalling the new relay by reversing the process.