Some boat owners like to maintain their own engines, it's good to know how they work and what to do to keep them in good order.


DIESEL FUEL SYSTEMS - safety precautions

Diesel fuel systems operate at both low and extremely high pressures. Some components have fluid connections to both low and high-pressure sections (injector pumps) and it is sometimes easy for the in experienced to confuse the two, especially in adverse working conditions. A leak in the high pressure system can produce an intense spray of fuel, this can penetrate the skin, it can "spray" atomized fuel which can ignite to cause fire, be hazardous to health.  It's advisable to apply the same precautions to all parts of the fuel supply system.


Routine Maintenance

Routine maintenance of diesel engines is an important factor in the reliability and longevity of diesel engines. With proper maintenance these engines will run for many thousands of hours, often under harsh environmental conditions. If they are not looked after however, small faults can lead to serious engine damage in a very short time.

Many diesel engines are converted small commercial vehicle engines (mainly light vans and trucks), Routine maintenance is much more important on these engines, than simply following a list of "things to do" taken from a vehicle hand book, these engines were not designed for the marine environment and will not have the same toughness or resistance to corrosion as a marine or industrial motor.


A skilled technician will spot potential problems early, allowing prompt action to prevent more complicated faults developing. Filter replacement Fuel filters prevent potentially damaging particles getting into the sensitive components of the diesel injection system and as such are a vital part of the diesel fuel system, and they need to be replaced at regular intervals. Just by doing the job they were designed to do, that of preventing anything other than clean fuel proceeding further along the fuel system towards the engine, they retain these particles and will eventually become clogged.


Filters will naturally retain almost any foreign bodies entering the fuel system including particles of dirt, fluff from rags and paint flakes from the inside of tanks and cans. In some cases, when the temperature is very cold, typically below -15°C, the filter may also retain crystal deposits formed from natural waxy elements within the fuel itself. Over time the flow of fuel through the filter will be reduced by the particles retained within the element, and when this flow reduction reaches a critical point the lack of fuel flowing to the injection system will eventually promote engine misfiring, stalling and even non-starting. This is the point at which the filter is often described as being "blocked".


In many fuel injection systems the fuel serves as a lubricant and damage can be caused to vital components if the fuel flow is sufficiently reduced by blocked filters. Service intervals are designed to help ensure that the filter is replaced before the build-up of dirt etc. within the filter becomes excessive. Water is often present in diesel fuel, normally caused by condensation in the boats fuel tank and in tanks where the fuel is stored prior to reaching the vessel. Most filter assemblies incorporate a drainage system to allow water to be removed at regular intervals and to drain the assembly when replacing the filter. Water collecting in the system is damaging to injection system components and may cause engine running/starting problems.

It is best to have at least one water separator (pre-filter) in the system, for preference close to the tank with shut off valves both sides to isolate it. DIESEL ENGINES DO NOT RUN ON THE WATER THAT CONTAMINATES THE FUEL TANK!