7 common 6.5 Diesel Injection Pump Failure Symptoms (Fix guide)

A diesel injection pump is one of the vital components of an engine. And a bad injector can make a horrible riding experience. So, you must solve the issues before it slowly kills your engine.

And there are various 6.5 diesel injection pump failure symptoms. As a technician, I have seen the following symptoms most in 6.5-liter diesel engines.

Engine misfiresCombustion component malfunctionReplace air filter or fuel filter
Engine surgesClogged fuel injectorClean properly
Lack of accelerationInjector is not workingReplace the fuel injector
Fuel leakageInjector brokenReplace it
Trouble startingLack of fuelRepair the faulty injector
Low fuel economyLeakage in fuel lineRepair leakage by checking fuel line and injector
Bad smellFuel leakingCheck the fuel line and injector separately to find the leakage and fix it

If the injection pump has any issue, you will notice it while starting. Trouble in starting is the common symptom of a bad injection pump. If the reason that causes injection pump failure is serious, then you need to repair it quickly.

So, I have indicated the issues and the reason behind them. Let’s focus on the details to deal with this issue.

6.5 diesel injection pump failure symptoms
6.5 diesel injection pump

Read also >> How Do I Know If My 6.0 Powerstroke Fuel Pump Is Weak?

7 sings to detect 6.5 Diesel Injection Pump Failure

Since you have come this far, let’s talk about each symptom and find the proper solution. Enjoying driving without stalling your engine by solving the issues is necessary.

#1. Engine Misfires

It is quite an annoying problem while trying to accelerate your car. Due to the malfunction of combustion components, it cannot reach a high speed.

However, it runs perfectly under 40 miles and starts problems at a higher speed. And you will hear the engine splutter. You need to clean the engine and check possible damages. Some cases require the replacement of the combustion parts such as fuel filters, air filters, etc.

#2. Engine Surges

It is a similar problem that happens on the road. Imagine a scenario you are going at steady acceleration, but suddenly your car is getting fast or slow. That is because of the engine surge problem. And it can happen due to the bad fuel supply. One or more clogged fuel injectors can cause this issue.

Therefore, you have to check each injector, and cleaning will do the job.

#3. Lack of Acceleration

When the engine is not getting enough oil, you cannot expect throttle power from it. The problem lies in the fuel injection pump. There could be one or more injectors not delivering fuel to the engine.

As a result, the car is not getting the prime power. If you get this problem after cleaning the fuel injector pump, you need to replace it with a permanent solution.

#4. Fuel Leakage

If you see fuel leaking from the engine, that surely comes from the injection pump system. Whether it is the fuel line or injection pump is broken. And trying to seal the leakage is not a solution here. In this case, you have to replace the fuel line or injection pump to come up with a solution.

#5. Trouble Starting

When the ignition works and creates enough spark, but the car is not starting, that’s because of the lack of fuel. Due to the faulty injection pump does not deliver enough oil to start the engine from the spark.

So, you need to check each injector separately and clean it if needed. In some cases, you need to replace that faulty injector.

#6. Low Fuel Economy

Usually, when the engine does not get enough acceleration, it tries to power up and ask for more fuel to reach the speed. At the end of the day, it will burn more fuel without getting the extra miles it should be.

Also, the injection pump leakage can cause a similar problem by constantly leaking oil. If that happens, there is no chance of replacing the fuel line and finding the leakage to do some permanent solution.

#7. Bad smell

It comes from fuel leakage. When your engine leak fuel constantly, you will get a bad smell while driving the car. And it is also a vital issue that you need to take care of immediately. As I said, you need to find the leakage and replace that part in the injection pump.

You can also read 7.3 powerstroke PCM failure symptoms and their solutions. It might be helpful for you too.

What Causes 6.5 Diesel Injection Pump Failure?

You know the symptoms of injection pump failure, but why does it happen? The prime reason behind it is the dirty fuel. Let’s check the reasons.

  • Poor quality fuel causes massive damage to the injection pump as well as the entire car engine.
  • Also, running your car at low fuel puts pressure on the injection pump to supply fuel to the engine. As a result, it quickly becomes faulty.
  • Or, maybe the parts are too old to perform at the peak to supply similar fuel.
  • Moreover, injector timing malfunction can cause similar consequences.

How Serious Is The 6.5 Diesel Injection Pump Failure?

Whether a diesel injection pump or other fuel injection pump fails, it is going to slow down or shut the entire engine. The Importance of a diesel injection pump is no way to ignore. An injection pump provides the right fuel to the engine to run it smoothly.

Also, it adjusts with the engine’s speed to ensure the right amount of fuel flow. Therefore, it keeps the engine running without causing the issue.

What To Do When 6.5 Diesel Injection Pump Failure Symptoms Appear?

So, when you see any signs of bad 6.5 diesel injection pump, you should check the engine or go to the repair shop to solve it quickly. Otherwise, it will cost massive damage to your car engine. Eventually, the symptoms you are going to see in the car are crucial for driving.

For example, if you do not get enough acceleration, the car will slow or cause a severe accident.

And fixing the injection pump will not cost you a massive amount of money if it only requires cleaning. Also, a simple repair is not expensive. However, replacing the 6.5 diesel injection pump is more than 2000 USD.

Injection Pump Failure related (FAQs)

Let’s check the answers to popular questions regarding bad diesel injection pump.

How Do You Test A 6.5 Diesel Injector Pump?

Open the T valve while ensuring the engine is running. And wait for 30 seconds to drain the fuel. If the engine dies before 30 seconds, there are some issues with your injector pump.

Why Does My Diesel Truck Crank But Not Start?

Because the engine is not getting enough fuel to fire, a bad fuel injector pump is its prime reason.

What Does A Bad Injector Pump Do?

It causes various engine problems, eventually making the driving experience worse. Also, a bad injector pump is a reason for low fuel economy.

1999 Chevy diesel 6.5 Bad Injector pump demonstration >> Check out the video below:

Take Away

6.5 diesel injection pump failure can cause severe damage to the car engine. Therefore you should repair it before it goes too bad. Check the fuel before pouring it into the car or get it from a renowned gas station. Also, should checkup your car regularly to remain safe.

And if you see an acceleration problem, bad smell, or engine surges, go to the nearest repair shop to check the engine and get the right solution. Since replacing the injection pump of a 6.5 diesel engine costs too much money, you should get a checkup regularly.

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Mahir Ahmed


I'm the guy responsible for ensuring honest, informative, accurate and helpful guide to the reader.

3 thoughts on “7 common 6.5 Diesel Injection Pump Failure Symptoms (Fix guide)”

  1. I have a 65 turbo diesel from a 95 GMC when I step on the accelerator sometimes the engine stays at an idle and doesn’t rev up only happens occasionally

  2. I have jst replaced a fuel injector pump on an Isuzu KB 250 but now it only starts with a quick start, some 1 said it needs to be advanced, is this true?

    • Makalima, it’s possible that the timing on the injector pump needs to be adjusted, which is sometimes referred to as “advancing” the pump. The timing of the fuel injection pump regulates when fuel is injected into the engine’s cylinders, which is critical for smooth and efficient operation of the diesel engine.

      The symptoms you’re describing could indeed be due to the pump not being correctly timed, which could cause hard starting or require the use of quick start to get the engine running. Other symptoms of incorrect pump timing can include poor fuel efficiency, reduced power, or excessive engine noise.

      Please note that timing a diesel injection pump is a complex task that requires a deep understanding of the engine’s workings. It typically requires specialized tools and expertise, and therefore should usually be performed by a trained mechanic.

      Always remember that while it’s possible this could be the cause, hard starting can be caused by a variety of factors in a diesel engine, including issues with the glow plugs, compression, fuel quality, and more. A full diagnostic check-up from a professional mechanic will give you a more definitive answer.


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