Figure 5-40.-Typical diesel engine glow plug.

before normal initial starting. The glow plug (fig. 5-40) resembles the spark plug of a normal gasoline engine. The system is operated manually by depressing a switch or button; or, it may be turned on with the ignition switch and turned off by a timed relay. During colder weather, the system, with the relay, may have to be run through more than one glow plug cycle to start the engine.

Glow plugs are not complicated and are easy to test. Disconnect the wire going to the glow plug and use a multimeter to read the ohms resistance of the glow plug. Specifications for different glow plugs vary according to the manufacturer. Be sure and check the manufacturer's repair manual for the correct ohms resistance value.

The manifold flame heater system (fig. 5-41) is another type of cold starting system found on diesel

Figure 5-41.-Manifold flame heater system.