Diesel engines use the Elettrostart solenoid to control the cam that sends fuel to the injectors. When the motor starts up, the magnetic force loads the spring. The electromagnet remains energized while the motor is turned on. During the stop phase, the electromagnet is no longer energized, and the spring shuts off the flow of fuel.

They can be dual-coil (E and ES, continuous duty) or single-coil (D and DS, intermittent duty).

In dual-coil electromagnets, the main coil performs the traction (or push-pull in the ES models), and the auxiliary coil is a low-consumption holding coil. These are used for continuous work, regardless of the number of hours operating. The primary (starting) coil comes into play in the first phase only, causing the plunger to generate an elevated force-stroke response. By using the plunger to press on a microswitch or by using an external command, the starting coil can be disconnected mechanically.

Energized single-coil electromagnets allow diesel motors to be shut off, commanding the fuel-feeding cam and cutting off the flow. Due to the high performance power, the service is intermittent. The insertion time must not exceed one minute, while the disconnection time between two insertions must be long enough to allow the electromagnet to cool down.

Choosing the appropriate electromagnet

The reference of the Elettrostart solenoid deserves some explanation. The first letter refers to the construction system: E – simple effect, ES – dual effect. The first number reflects the diameter of the body: 4 = 40mm, 46 = 46mm, 5 = 50mm, 6 = 60mm. The second number indicates the voltage (1 = 12V, 2 = 24V). The third number refers to the mounting system (series). Letters A, B, and C indicate the mounting bracket (A is the standard).

Series 1 and 2 electromagnets have an internal switch. A direct electrical circuit is used in series 1, while a combined electrical circuit and starter motor are used in series 2. Series 3 electromagnets do not have an internal switch.

Installation of an Elettrostart solenoid

When assembling the motor, in order for the holding coil to activate, the rod must reach the end of the stroke, with the plunger adhered perfectly to the plunger guide. Furthermore, it must be configured with the maximum force-stroke of the Elettrostart solenoid. This simplifies the installation alongside the injection pump to command the shut-off and ensures optimum adjustment of the acceleration control. In solenoids with internal electronic contacts, proper mounting and a regular source of power prevent the coils from overheating. To protect it from motor vibrations, the nuts and washers must be sealed where the solenoid connects to the pump with Loctite or paint. The placement of the solenoid must respect the alignment between the direction of movement of the plunger and that of the brace to which it is connected, since misalignment could cause friction and loss of power. Likewise, the workload is diminished if the solenoid is placed too far away from the operating position.