How Many Performance Issues Can Be Traced to a Faulty Diesel Pump

Posted on: 30 June 2018


Are you having issues with your diesel engine? You may notice some odd behaviour in a variety of different driving conditions and may find it difficult to put your finger on the issue. While there are several places to look for an answer, one of the first things to check is the diesel pump. This may be a relatively small and simple device, but it can cause all manner of issues when it's not working properly. Could this be the source of your unexplained problem?

How the Pump Works

Years ago, a mechanically-operated pump would be responsible for delivering fuel to the engine. It was typically mounted in between the tank and the engine itself and had a simple diaphragm within to regulate delivery. Today, vehicles rely on an electronic pump that's designed to cope with the injected engines of the modern-day era and can deliver a lot more pressure than its predecessor.

Typically, a diesel pump is located within the tank. It needs to push the fuel all the way to the injector at a uniform level of pressure so that the engine can operate efficiently under all types of load.


When the pump starts to malfunction, this can lead to a variety of problems. When you're driving along at a constant speed, you may notice that the engine will hesitate or splutter, which is a sign that the diesel pump is only delivering intermittent pressure.

Unpredictable Driving

As if this wasn't annoying enough, you may also find that the vehicle is very unpredictable when you accelerate from a standing stop. This is the moment when the pump is under maximum load as it must increase pressure instantaneously when the engine demands more fuel.

Unwanted Surge

If you are sitting at a traffic light and waiting for it to turn green, does the vehicle sometimes surge forward by itself? In this case, it's lucky that you have your foot on the brake! Here, the diesel pump is not providing any more resistance and fuel is being sent to the engine when it's not needed.

The pump must regulate the supply of fuel as well as deliver the right amount of pressure, and if the pump has started to malfunction, it may not be able to prevent an unwanted surge.

Complete Failure

As things get worse, these symptoms will become even more apparent. Eventually, the pump will fail altogether, and the engine will not start.

Proceed with Caution

You may think that you can fix this issue and replace the pump yourself and while this is technically possible, remember that this is a very dangerous, combustible environment. Most people will go to a mechanic for car repairs.