Diesel Fuel Pump Failure Symptoms

The diesel fuel pump makes up part of the fuel injection system. It is responsible for drawing fuel from the tank and directing it to the injector.

The fuel system and ignition will fail when the diesel fuel pump fails. An ignition system in a car needs fuel to work. The fuel in the engine is what will be ignited to start the vehicle. If the pump does not work, the engine will have no fuel.

Other symptoms will begin to come up like, loss of power, engine stall, misfire, etc.

It is important to note that symptoms like this can harm the engine if not checked and fixed. For instance, engine misfiring can unbalance the engine, which will cause it to shake uncontrollably and also damage internal components.

Knowing the symptoms of a failing diesel fuel pump will help you identify the problem faster. It will also give you an idea of the cause of the issue.

diesel injector pump troubleshooting

Diesel fuel pump types

There are three significant types of diesel fuel pumps, and they are:

  • Rotary Pump
  • Inline Pump
  • High-pressure common rail pump

The three fuel pump work quite differently but serve the same purpose of drawing fuel from the fuel tank and moving it through the system until it reaches the combustion chamber.

Rotary Pump

The engine powers the rotary pump through the drive shaft. It has a circular design that allows it to be connected to an output line. The output line is connected to a distributor powered by the driveshaft.

As the drive shaft rotates, a vane pump fitted over the drive shaft causes a suction in the pump body. Diesel fuel is drawn from the tank and directed to the pump body.

The diesel is pressurized once the vane pump fills the rotary body thanks to the drive yoke and cam plate. Once the fuel reaches a particular PSI, which is around 3300 psi, it is then moved by the distributor (plunger) to the injector through the pressure pipeline. The injector then sprays the pressurized diesel into the combustion chamber.

The rotary diesel pump only uses one distributor or plunger delivered to a single injection cylinder.

Inline Pump

The inline pump is a lot similar to the rotary pump. However, there is a difference. It is powered by the engine through the camshaft, just like the rotary pump. The engine determines the timing of the pump and its speed.

Also, it uses the lift pump that draws fuel from the tank into the pump. It is then pressurized.

What makes the inline pump different is that each cylinder operates independently. There are four cylinders (depending on the engine type), each cylinder with its injector and plunger or distributor.

The camshaft drives each plunger or distributor, delivering fuel to the injectors.

High-Pressure Common Rail Pump

This type of diesel pump is much more different than the inline and rotary pumps. It is more like the HEUI oil pump.

The pump has one inlet, two outlets, and a revolving piston. The outlets are connected to a rail which supplies fuel to the pump. Fuel is continuously fed into a high-pressure accumulator, which helps maintain the pressure.

Furthermore, the pump handles the pressure of the fuel, and then the ECU takes care of the distribution of the fuel with the help of solenoid valves on each injector. The valve receives signals from the ECU, which controls high-pressure fuel delivery to each cylinder. 

How does Diesel Fuel Pump work?

The fuel pump draws fuel from the tank and then delivers it to the injection system to be sent to the engine for combustion. It draws fuel from the tank through fuel lines, then delivers it to the fuel injector via the filter.

Once the pump delivers diesel to the injector, it is sprayed into the combustion system.

There are two majors types of fuel pumps, they include:

Mechanical Pump

The mechanical diesel fuel pump relies on the engine for power. The engine powers it through the auxiliary belt or chains. As the engine rotates the belt, so is the camshaft.

As the camshaft rotates, a rubber diaphragm is pumped up and down. It creates a function that aids in pulling fuel into the pump. A valve in the fuel line ensures that the diesel fuel only flows in one direction, towards the engine.

Electronic diesel fuel pump

The electric diesel fuel pump can be found in vehicles that use electric diesel fuel injection. It works with the help of an electric motor. Once electricity is sent to the engine, fuel is drawn from the tank to the injector.

Unlike the mechanical diesel fuel pump, the pump is inside the fuel tank. It allows the device to draw fuel easily. However, some are mounted outside the tank, depending on the vehicle.

How does the fuel pump work? The Engine Control Unit (ECU) will energize the relay once the engine starts. The relay then supplies current to the fuel pump.

In addition, the motor in the fuel pump will spin, creating pressure in the fuel system. The ECU has a timer to limit the activities of the pump.

Diesel Fuel Pump Failure Symptoms

Most drivers should be familiar with Diesel Fuel Pump Failure symptoms. Below are some symptoms to watch out for.

Engine Misfires: A clogged fuel pump or mechanical issue can cause the pump to send inadequate fuel to the injector. When this happens, the engine will receive too much or insufficient fuel.

The inconsistency in the fuel going to the engine will cause the combustion system to function inadequately, and some cylinders will remain unfired.

Loss of Power: A leak in the pump or clogged lines will prevent sufficient fuel from entering the engine. Now, the power created by the engine depends on the amount of fuel that goes into the engine.

When fuel is hindered from getting into the engine, then the power created by the engine will also drop.

Engine Stalling: A stalling engine is a sign that insufficient fuel is going into the engine. It shows the engine has lost power due to the damaged fuel pump.

Engine will not start: Fuel plays an active role in the ignition process; without fuel, there will be nothing in the engine to ignite.

A damaged fuel pump will completely stop the engine from starting. Damages like blockages, leaks, and damaged internal components will not allow fuel to get to the engine. As a result of this, the engine will not start.

Increased Fuel Consumption: A deteriorating fuel pump may not deliver the right amount of fuel, leading to increased fuel consumption and reduced fuel efficiency.

How to Test Diesel Fuel Pump

Testing the diesel fuel pump can help diagnose potential issues and confirm if it’s the cause of engine problems. Here’s a simple method to test the fuel pump’s functionality:

How to Test Diesel Fuel Pump

Fuel Pressure Test: Use a fuel pressure gauge to measure the fuel pressure by attaching the device t the pulse connected to the fuel pump. Compare the readings with the manufacturer’s specifications to determine if the pressure is within the correct range. A fuel pressure regulator also helps with this test.

Listen for Unusual Noises: If the fuel pump is broken, it may make strange whistling, buzzing, or clicking sounds. Use a stethoscope or close your ear to the fuel tank while the engine is running to listen for strange sounds.

Check the Fuel Pump Relay: Inspect the fuel pump relay for signs of damage or corrosion. A faulty relay can prevent the pump from receiving power, leading to fuel delivery issues. Always keep an eye out for signs of a faulty fuel pump relay.

What causes diesel fuel pump failure?

Several factors can contribute to diesel fuel pump failure:

Contaminated Fuel: Water, dirt, or other impurities in the fuel can damage the fuel pump’s internal parts, causing them to wear out and stop working.

Also, the contamination can accumulate in the pump or fuel line, hindering the pump from receiving or delivering fuel.

Low Fuel: When your tank is too low, air may get into the system. If you drive with too little gas, it could cause damage that will need diesel repair. Also, note that driving in cold weather may affect diesel levels.

In addition, diesel fuel is used to lubricate diesel fuel pumps. When the engine is run on low fuel levels or with bad-quality fuel, the moving parts of the pump experience increased friction and wear.

Overheating: Excessive heat can cause the fuel pump to overheat and eventually fail. When the fuel is heated and gets to the pump, it will cause it to overheat, which will also affect the engine.

When the pump overheats, internal components will fail, affecting fuel delivery to the engine.

An overheated pump could be caused by weather conditions, engine overheating, etc.

Fuel Additives: Using incorrect or excessive fuel additives can damage the pump, particularly in modern high-pressure standard rail systems.

Additives with corrosive agents can eat away the rubber or plastic parts of the pump, causing leaks and more.

Electrical Issues: Electrical problems like a faulty relay or wiring in electronic fuel pumps can cause the pump to malfunction.

Important tips and tricks to Reduce Premature Diesel Fuel Pump Failure

Use High-Quality Diesel Fuel: Always fill up your vehicle with high-quality diesel fuel from reputable sources to minimize the risk of contamination.

Do not start your vehicle if you have accidentally filled it with petrol fuel; instead, call your mechanic and arrange to have it towed to a service station where the gas will be drained from the tank.

Regular Maintenance: Follow the manufacturer’s recommended maintenance schedule, including fuel filter replacements, to keep the fuel system clean and running smoothly.

Keep Fuel Levels Adequate: Avoid running the vehicle with low fuel levels to ensure the fuel pump receives sufficient lubrication and cooling.

Avoid Overloading: Do not overload the engine, as excessive strain can put additional stress on the fuel pump and other components.

Check Fuel Additives: If you use fuel additives, ensure they are compatible with your vehicle’s fuel system and use them in the correct proportions.

Address Issues Promptly: If you notice any symptoms of a failing fuel pump, address the issue promptly to prevent further damage to the engine and fuel system.

How long does a diesel fuel pump last?

On average, a well-maintained diesel fuel pump can last anywhere between 100,000 to 150,000 miles.

The lifespan of a diesel fuel pump can vary depending on several factors, including the vehicle’s make and model, driving conditions, maintenance, and the quality of fuel used.

However, some pumps can last even longer, while others may experience premature failure due to adverse conditions or neglect.

Final Words

The diesel fuel pump, including the diesel injector pump, is a crucial part of how a diesel engine works.  Understanding the signs of a failing fuel pump, how to test it, the most common reasons it fails, and how to avoid it can help car owners make sure their fuel system lasts as long as possible and works well.

Regular upkeep, using high-quality fuel, which includes the prevention of the use of contaminated diesel fuel, and taking care of problems quickly are all important ways to make a diesel fuel pump last longer and avoid expensive repairs. Drivers can have a smoother and more effective experience on the road if they are aware and take action.

Akindayini Temiloluwa

I am passionate about everything automotive. Right from when I got my first toy car as a kid, I developed an interest in the inner workings of vehicles. As I grew up, my love for mechanical stuff became more substantial enough for me to pursue a career in it. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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