If your engine is a modern, modified, automotive unit it is likely to stop just like a petrol engine, when you turn the ignition off. To accomplish this is an electromagnetic solenoid valve is built into the injector pump. This type of valve needs a supply of current to allow the engine to RUN. This type also needs a supply of current to BLEED the fuel system.

At some engines (Bukh) use a visually similar valve, built into the injector pump, which is only supplied with current to STOP the engine.

Other manufacturers and mariners fit a solenoid to the injector pump’s mechanical stop lever (where the stop cable would normally be fitted). Electrically this type of stop system requires a current supply to STOP the engine. If the engine were within two or three metres of the steering position I would say that the solenoid needs removing and being replaced with a stop cable. That way one ends up with a simple, robust system that does not suffer from wiring and other electrical faults.

So if you have an electric stop control you need to find out if it needs current to STOP or current to run, once you have found that out, you can decide how to wire it up.

 

 

 

 

 

 

 

 

 

Connect the buzzer between the ignition switch terminal that is feeding the stop solenoid and any convenient negative point. Later in the book we will look at instrumentation and that will show a negative busbar for the engine electrics.

The thickness of cable for the buzzer is not critical – unless you are into electronics you are unlikely to possess any cable that is too thin.

The solenoids that move the mechanical stop control often draw quite a high current, so you are advised to use a heavy piece of cable, although the solenoids built into the injector pump draw rather less current.

The diagrams for both types of "current to STOP" solenoids are shown below.

The dotted negative cable is shown because some of the separate solenoids have two connections and are "insulated return" so require the dotted negative return cable. Other solenoids only have one terminal so are "earth return" – their return current flows through the engine to the main negative connections, so the dotted line is not needed.

Remember to fit the buzzer, as shown above, if your switch does not "spring back to OFF", alternatively fit a push switch to operate the stop solenoid.

The starting circuit and the "current to stop" circuits are not normally fused because they spend most of the time turned OFF and if a cable did short and start to smoke the natural reaction is to turn the switch OFF.

Some diesel engines, especially those derived from light automotive designs cannot get the air in the cylinders hot enough to ignite the fuel under cold conditions. These engines are fitted with an electric heater in each cylinder. We know these heaters as GLOW PLUGS or HEATER PLUGS.

Other engines are supposed to start well enough for most of the time and are fitted with a single electrical heater in the inlet manifold or the back plate of the air cleaner. The Perkins 410/x series of engines have a special hollow "FLAME PLUG" fitted into the manifold. These are connected to a fuel supply, so in very cold conditions electricity heats the electrode in the plug and fuel is drawn through the hollow plug. This produces a "blow lamp" type flame inside the inlet manifold.

Very modern automotive practice is to employ glow plugs, operating on reduced power once the engine starts, to reduce diesel knock and thus minimise annoying the neighbours when cold starting and warming up in the morning. These systems use complicated timer/resister/relay systems but as noise is not normally an issue in marine use I see no reason why the complicated control systems cannot be dispensed with. One would just use a slow count to 30 as a timer and put up with a bit of noise and possibly smoke for a few minutes of running in the interests of reliability and simplicity.

This is the circuit for the old 2volt heater plugs. The inverted triangle symbol on the right shows the negative connection either to the engine block or battery negative.

If the resistor fails and is unobtainable, the problem could be solved by mounting two of the plugs in a ventilated metal box, thereby coupling six plugs in series.

The diagram above shows how the 12 volt plugs are connected together. They "earth" through their metal bodies to the main battery negative connection.

The last diagram is for one of the modern circuits that keep the glow plugs turned on at reduced power once the engine is running. It also uses a warning lamp to tell you when to attempt to start the engine. My advice would be to ignore this type of system and avoid the complexity of the extra sensors, connections, relays and the electronic control unit.

Complete diagrams

 

 

 

 

 

 

 

 

 

This is the simple 12 volt glow plug circuit.

Locate the fuse in a fuse box, close to the instruments and inside the accommodation if possible.

Because of the different current ratings for these plugs you need to measure the current your particular plugs draw.

If the ignition switch is more than two or three metres from the engine I would advise the use of a relay of solenoid as shown below.

Only the 12volt plugs are illustrated, if you are using the 2volt version simply substitute the plug/resistor diagram for the glow plugs shown.

NOTE – the diagram shows a high current (180-amp) relay. If you are using an inertia starter solenoid wire the ignition switch to the small terminal, connect the case to battery negative in some way (see solenoid section above) and connect the two large terminals between battery positive and the glow plugs.

Note the dashed alternative of wiring the negative back to the main negative terminal on the engine block if other components require this form of connection.