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October 1

Repairing a leaking diesel pump

A common problem we see at Morrison Diesel is a leaking diesel pump. A customer may have noticed diesel leaking from the engine area. Another symptom that may indicate a diesel pump leak is a vehicle which doesn’t start properly. However in many cases the customer has been unaware of the problem until their vehicle fails a WOF inspection because the diesel pump is leaking.

The function of the diesel pump (also known as a fuel injection pump) is to deliver highly pressurised fuel to the injectors, which in turn inject the fuel into the cylinders. The diesel pump controls the quantity and timing of fuel delivery with absolute precision. Unlike a petrol engine the diesel engine does not use spark plugs to ignite the fuel; instead ignition is brought about in the cylinders by conditions of extremely high pressure and temperature. We could liken the diesel fuel pump to a sturdy heart that continuously pushes fuel through the diesel engine, working with great accuracy and speed in intense conditions.

Over the years the design of diesel pumps has evolved, from inline pumps which have a separate plunger for each cylinder, through rotary (or VE) pumps which use a single rotating plunger to distribute fuel to each cylinder in turn. An alternative design is the unit injection system in which a high pressure pump is incorporated into each injector. Finally, the common rail pump, found in most modern diesel vehicles, delivers highly pressurised fuel to multiple injectors via a single fuel rail.

Whatever the design of the diesel pump, it will have a number of seals (and occasionally gaskets) around it which serve to contain the diesel fuel. Over time these seals can harden and become brittle, and then diesel fuel will start to leak from the pump. Removing the diesel pump from the engine is a time consuming task for a mechanic, and as all of the seals will age at a similar rate we recommend replacing every seal (a full ‘seal kit’) while the pump unit is out of the vehicle.

The task of disassembling a pump, replacing the seals, and then reassembling the pump correctly, is a highly technical procedure that should only be completed by a diesel specialist. At Morrison Diesel you can be confident that the job will be done right. We have extensive experience of fitting new seal kits to diesel pumps and receive work of this kind from around the country and beyond. All work at Morrison Diesel is guaranteed and if you chose to investigate the marketplace you will find that our prices are very competitive. Please contact us for any further advice you may require regarding your diesel fuel pump.