Reasons Why Your Fuel Injector Pump Is Failing and How to Fix It

Everything you need to know about injector pumps

Reasons Why Your Fuel Injector Pump Is Failing and How to Fix It
A diesel fuel injector pump is a mechanical device that usually pumps diesel into the automotive engines’ internal combustion chamber. Pinterest

Fuel injector pump performance is closely related to your engine performance. If your diesel car has a fuel supply issue, it will starve to death. Fuel injection problems are, therefore, the toughest problems to deal with. Whether you’re experiencing issues with your engine or not, it helps to know about fuel injector pumps, how it affects your engine performance, and how to maintain them to avoid future problems.

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What’s a diesel fuel injection pump?

A diesel fuel injector pump is a mechanical device that usually pumps diesel into the automotive engines’ internal combustion chamber. It’s the diesel engine’s heart, where it maintains its rhythm to keep it running efficiently for decades to come. Diesel injector fuel is important because:

  • It feeds fuel to your engine to keep it running. This is done by compressing the fuel to high pressure where it’s lifted to the plunger, and then sent to the injectors.
  • It adjusts fuel quantity. When the quantity of fuel injected is adjusted with engine speed, and the timing remains the same, the outcome and the fuel dissipation will change. The accelerator is adjusted when the output of the engine is directly proportional to the injected fuel quantity.
  • It’s used to adjust the injection timing. The diesel injection pumps manage the timing from where the fuel is injected, ignited, and combusted when maximum combustion is reached.
  • It’s also used to atomize the fuel to improve the ignition, which usually results in full combustion.
Reasons Why Your Fuel Injector Pump Is Failing and How to Fix It
High-performance vehicles typically have one fuel injector per cylinder. Pixabay

High-performance vehicles typically have one fuel injector per cylinder, and the pump injects the diesel into the combustion chamber, hence the name fuel injector. The fuel (diesel) is then dispersed from the injection pump to the combustion chamber through another process. During this process, pressurized fuel enters the fuel injector based on a signal from an electronically controlled valve, then to the plunger, which prepares the fuel for the final exit. When the fuel moves from the fuel injector, a spray tip distributes the fuel as a fine mist.

Diesel fuel injection pumps are performing at a higher pressure than they were ten years ago. It was typical for fuel injector pumps to process fuel in the fuel system at around 10,000 to 15,000 PSI (Pounds per Square Inch). Compared to how engines operate today, that’s just half of the work. Today, diesel injection pumps are running at the 30,000 to 40,000 PSI range.

High-end engine performance is, in many ways, attributed to how much fuel the engine can process. This means that a superior engine will process air and fuel much better than an average engine – that’s one reason people are also using turbochargers to increase horsepower. It also explains the higher pressure output of today’s fuel injection pumps than 10 to 15 years ago.

Common diesel fuel injection pump failures and how to prevent them

There are two significant causes of diesel injector failure, and 90% of the issues can be traced to the quality of the fuel you’re using, or rather, the lack of quality and faulty mechanical problems in the fuel injector housing. From these two things, several issues may arise. Let’s look at the common fuel injector pump complications.

Dirty fuel

Using subpar or dirty fuel is one of the common reasons that can cause your fuel injector pumps to stop working efficiently or entirely. Overtime residue like gunk and grease can build up inside the fuel system and clog up the entire fuel injector pump. The area that you should look out for because it’s most susceptible to clogging up is the spray tip, which is the area where fuel exits the injector onto the combustion chamber.

If you notice your engine hesitating and sputtering when trying to accelerate, this is a sign that your injector pumps may be clogging up.

Driving on low fuel

Driving with your fuel tank almost empty is extremely bad for your diesel engine. You should at least try to keep a third of the tank full at all times, because of the lubrication the fuel provides to the fuel injection pumps. When there’s enough diesel in your tank, the fuel pump bearings are adequately lubricated.

If the tank runs on empty, air then enters the tank and can quickly wear out your bearings, and prevent the injector pump from getting the fuel at the proper pressure levels.

Reasons Why Your Fuel Injector Pump Is Failing and How to Fix It
Driving with your fuel tank almost empty is extremely bad for your diesel engine. Pixabay

Deposits in the injector pump

One of the major reasons for injector pump failure is an excessive buildup of deposits. There are two types of deposits – internal injector deposits and external injector deposits.

External injector deposits are caused by fuel that’s not wholly burned that often builds up around the injector holes. These deposits are what are referred to as coking deposits.

While, in some cases, these deposits won’t lead to injector failure, they can build up enough to obstruct the fuel spray, which will lead to less efficient fuel combustion. You’ll notice this if your vehicle has noticeable power loss or very high fuel consumption. To successfully rid your diesel engine of these external deposits, you can use detergent additives, which work just fine. They will help restore your injector pump to its most efficient performance, restoring both the lost power and increased fuel use caused by the buildup of the external deposits.

In previous years, there has been a new type of injector pump deposit, the internal diesel injector deposit. This deposit doesn’t build on the injector’s external tips, but they form on the inner parts like the pilot valves and injector needles. They look similar to the coking deposits, which are usually dark brown and light, or almost an off-white and greyish color. While they can build up in any diesel engine, they are more prone to form in the newer engines with highly engineered injection systems.

As these internal deposits build up, they create the same problems like those shown by external deposits – power loss and high fuel consumption. In severe cases where the injectors begin to stick completely, they can lead to high maintenance costs and excessive vehicle downtime.

Excessive wear

Your fuel injector pump can also fail due to excess wear. Up to 2006, diesel found in the United States contained high levels of sulfur; the sulfur came from refined crude oil. The sulfur in the oil is what acted as a lubricant for the fuel system. Diesel with relatively low amounts of sulfur was gradually introduced into the market called Ultra Low Sulfur Diesel (ULSD) and is now mandated in all diesel fuel segments, including railroads, on-highway, and off-highway.

As refiners removed the sulfur from diesel, the lubrication benefits went away as well. Now, additives are being used to restore lubricity in diesel. The less lubrication the diesel provides, the larger the wear scar. The standard for measuring lubricity in diesel is the HFRR (High Frequency Reciprocating Rig) test, which measures the size of the wear scar between two metal surfaces lubricated by fuel. Many diesel fuel distributors are now adding additional lubricity improvers to mitigate premature wear.

Reasons Why Your Fuel Injector Pump Is Failing and How to Fix It
It’s important to maintain precise timing every time your diesel engine’s timing belt has been adjusted or replaced. Pixabay


While fuel lubricity is a vital factor in determining excess wear in the fuel injection pumps, it’s not the only fuel-related cause of excessive wear. The other major cause of premature fuel injector pump failure is abrasion. All fuels, including the highest-quality diesel, contain small quantities of impurities.

Some of these impurities may include microscopic particles that can pass through even the tightest onboard fuel filters. If your diesel fuel contains these small insoluble particles, with time, they can abrade the injectors as they go through them during standard engine operation.

In extreme cases, the abrasion can significantly change the fuel spray pattern, causing reduced engine performance, high maintenance costs due to severe abrasion, and even increased engine downtime. Excellent housekeeping practices by the fuel supplier and proper fuel filtration can adversely reduce the damage caused by abrasion.

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Bad injector timing

The perfect amount of fuel and its timing is exceptionally vital because they regulate the combustion of fuel and the engine’s acceleration. It’s important to maintain precise timing every time your diesel engine’s timing belt has been adjusted or replaced.

Bad fuel injection timing may lead to low engine performance and can cause the engine to misfire. It can also cause overconsumption of fuel, loss of power, and excess smoke production. The severity of the problem will also depend on how far off the timing is. If the timing is slightly off, there may be minimal to no issues at all. If you need to have your fuel injector pump checked, don’t do it yourself, and instead, go to professionals who are familiar with diesel engines and diesel fuel injector pumps like Goldfarb inc.


Excellent fuel injection pump performance is crucial to maintaining a healthy engine. An engine that has prolonged fuel injection difficulties will deteriorate fast and eventually fail. Having an idea of the common problems with fuel injector pumps and how to prevent them will save you a lot of money.

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