The diesel fuel pump is the most complex and essential part of the diesel engine. It creates a high pressure of 15,000 psi or more on newer vehicles to maintain a fine mist of diesel needed for proper ignition. Therefore, the high-pressure fuel pump must be sturdy and durable enough to handle the pressure of compressed air and heat from the ignition.
But similar to other components of the car, high-pressure fuel pumps are also prone to periodic breakdowns. As a result, your car will exhibit signs of a weak high-pressure diesel pump, such as engine misfires, sputtering, stalling, delayed acceleration, and loss of power. A faulty high-pressure fuel pump will significantly impact your vehicle’s performance.
Therefore, we discuss the most common symptoms of a bad high-pressure fuel pump and the reasons for its failure.
What is a diesel high-pressure fuel pump?
The fuel delivery system of a diesel engine consists of a pump, fuel lines, and an injector to deliver fuel from the fuel tank to the engine. The diesel engine’s performance requires a constant fuel supply at all times, even at high speeds or under heavy loads. To do this effectively, it uses a high-pressure pump (diesel fuel injector pump) typically located inside or around the fuel tank.
Diesel high-pressure pumps deliver the fuel from the tank to the fuel injectors in the combustion chamber at extremely high pressure for optimal fuel-air ratio. High pressure is necessary for your diesel engine’s ideal performance and efficiency.
At the same time, the high-pressure pump also controls the volume of fuel needed to gain the desired power, depending on movement dynamics, engine temperatures, and other parameters.
How do I know if my high-pressure fuel pump is going bad?
If you’re keen, you can catch the symptoms of a failing high-pressure fuel pump and repair or replace it before it affects other parts. A failing high-pressure fuel pump will present one or more of the following symptoms.
Engine sputters
When driving at freeway speeds and notice your engine shaking, you may have a bad fuel pump. This happens when the fuel pump doesn’t deliver a consistent fuel flow into the engine. This unstable fuel flow causes the engine to skip several power strokes, forcing it to sputter and jerk.
In the early stages, the sputtering is usually mild and may be mistaken for issues with contaminated gas. Either way, the best solution is a new fuel pump.
Loss of power when accelerating
If your car sputters or loses power when accelerating from a stop, it’s likely an issue with the injector pump. Note that accelerating requires more fuel, thus forcing your pump to work harder. If your high-pressure fuel pump is damaged, it will not deliver fuel at the adequate pressure required for acceleration.
Increased engine temperature
Diesel engines require consistent and high-pressure fuel delivery for efficient performance. So if the pump fails to provide the proper amount of diesel to the engine, it becomes overstressed, resulting in an irregular rise in temperature.
Loss of power
Some driving activities such as, driving uphill or towing a load will stress your engine and demand more fuel to perform effectively. But if your fuel pump has gone bad, it won’t keep up with the increased fuel demand, which also puts more strain on the fuel pump.
Therefore, a faulty injector pump won’t be able to maintain a steady flow of diesel to the engine, resulting in loss of power during fuel-demanding situations.
Engine surges
Sudden surging of your vehicle is another sign of high-pressure fuel pump failure. A fuel pump with worn-out elements may cause sudden pressure changes in your fuel lines. Consequently, your vehicle will start easily and accelerate smoothly, but after a few minutes of steady speed, it surges forward or misfires.
The engine fails to start
If you ignore all the above injector pump problems, eventually, your vehicle will refuse to start due to a dead high-pressure fuel pump. In this situation, identifying a bad fuel pump is easy; when starting your vehicle, it will crank over but won’t stay on when you let go of the key.
Note: To confirm your injector pump is faulty, test the fuel pressure in your fuel lines with a fuel pressure gauge. If it reads zero, then your pump is likely dead. However, sometimes testing a high-pressure diesel pump requires specialized tools and machines. That’s why it’s important to consult a professional mechanic to diagnose and fix the faulty fuel pump before it causes further damage.
What causes diesel high-pressure pump failure?
Before troubleshooting your diesel pump, it’s important to understand why it’s failing. The following are the most common high-pressure pump failure causes.
Contaminated fuel
Rust, debris, dirt, and moisture can enter the fuel tank, through the fuel filter, and into the fuel pump. Over time, particles clog up the system causing the fuel pump to work much harder. This, in turn, causes stress and accelerated wear to other elements in the fuel pump, eventually leading to fuel pump failure. Th best solution is to clean the fuel tank and refill it with clean diesel.
Ensure you always purchase clean and quality diesel to prevent injector pump issues.
Driving on low fuel
Frequently driving with low fuel is dangerous for diesel engines. The fuel in the gas tank heats up much faster, causing the fuel pump to overheat and deteriorate quickly. It also forces air to enter the tank, leading to corrosion of the system’s components. This prevents the fuel pump from creating proper pressure levels.
Therefore, you should always keep a minimum of a third of the fuel tank fuel. This helps cool down your fuel delivery system and the fuel in the tank. It also lubricates the fuel pump bearings.
Poor injector timing
The correct amount of fuel and its injection timing is necessary as they regulate the fuel combustion and the engine’s acceleration. When the O-rings or ball seats of the pump are defective, the timing of the fuel delivery process is disrupted. Bad fuel injection timing leads to reduced engine performance, causing the engine to misfire.
It also leads to increased fuel mileage, loss of power, and excess smoke production. The severity of the issue will depend on how far off the timing is. The solution is a complete high-pressure fuel pump rebuild or replacement.
Clogged injector
All fuels, including the highest diesel quality, contain small amounts of insoluble impurities. Some of these impurities are so small that they can pass through the best fuel filters. These particles can accumulate over time in the fuel injectors and significantly change the fuel spray pattern, thereby reducing engine performance.
To reduce the risk of clogging your fuel pump and injector, change your fuel filter every 40,000 miles.
Excessive wear
Your diesel high-pressure fuel pump can also fail due to excess wear. Component wear causes leaking, resulting in a rich fuel reading or a thick carbon buildup. Several factors can cause your fuel pump to deteriorate, such as:
- Age: Even the best-maintained fuel pumps will deteriorate over time. High-pressure fuel pumps have several moving parts that experience normal wear, leading to the pump’s poor functioning.
- Abrasion: Tiny impurities that cross the fuel filter barrier will abrade sensitive parts of the fuel pump and cause premature wear.
- Inadequate lubrication: Until 2006, diesel contained sulfur which was the lubricant for the fuel system in vehicles. Unfortunately, sulfur compounds in fuel create air pollution when burned. Therefore, there was a government mandate to remove most sulfur from fuel to form Ultra Low Sulfur Diesel. This, in turn, means the diesel lacked its lubrication properties, causing premature wear. Fortunately, many diesel fuel distributors are working on adding additives to restore the lubricity of diesel.
What happens when a high-pressure fuel pump fails?
When the high-pressure fuel pump fails, it stops delivering fuel from the fuel tank into the injector in the combustion chamber. This means there will be no ignition or combustion, preventing the car from starting or moving. In severe cases, prolonged fuel injector pump issues will cause the diesel engine to deteriorate fast and eventually fail.
Before your high-pressure fuel pump fails completely, you will experience sputtering or stalling of the engine, poor acceleration, especially when driving uphill or carrying heavy loads, an overheating engine, sudden surges, and misfires.
Conclusion
If your diesel high-pressure fuel pump is defective or has died, you will likely encounter one or more of the many symptoms detailed above. Once you suspect a faulty fuel pump, it’s best to repair or replace it immediately. Driving around with a bad high-pressure fuel pump can leave you stranded or cause more costly damage to other parts of the fuel system or engine.