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What vehicles use the Cummins Engine

You can find the Cummins 6.7L Turbo Diesel engine in the:

  • RAM 2500 Heavy-Duty pickup truck
  • RAM 3500 Heavy-Duty pickup trucks
  • RAM 3500 Chassis cab
  • RAM 4500 Chassis cab
  • RAM 5500 Chassis cab
  • Nissan Titan XD Diesel Truck

Highly Rated Diesel Engine Repair

Common Cummins Engine Problems

Engine Not Starting or Hard to Start

One of the most frustrating issues you can face with a Cummins diesel engine is difficulty starting or the engine not starting at all. You can read more common Cummins FAQs here. Several factors can contribute to this problem, including:

  • Low engine compression: Insufficient pressure in the cylinders can prevent the engine from generating enough heat to ignite the fuel. This issue is more common in high-mileage engines and can be diagnosed with a cold engine compression test.

  • Low fuel pressure: Most starting problems result from inadequate fuel pressure. Ensure that the fuel tank has enough fuel, check the fuel pump’s operation, and verify the fuel pressure.

  • Low cranking speed: Cummins diesel engines require a rapid cranking speed for proper fuel injection. Cold weather can sometimes lead to low cranking speeds, resulting in hard starting.

  • Insufficient fuel supply: Damage to fuel supply pipes or a blocked breather can disrupt the fuel supply, making it difficult to start the engine.

  • Fuel quality: Poor-quality fuel can damage internal engine components, especially injectors, leading to starting issues.

Running Rough at Low RPM

If your Cummins diesel engine runs rough, even at low RPM, fuel-related issues are often to blame. Common culprits include:

  • Low fuel pressure: Fuel pressure problems can lead to rough running. Check the fuel tank’s level, inspect the fuel pump, and monitor fuel pressure.

  • Insufficient fuel supply: A steady fuel supply is vital for smooth engine operation. Ensure there are no damaged supply pipes and that the fuel tank breather is clear.

  • Fuel quality: High-quality fuel is necessary for optimal engine performance. Poor fuel quality can damage injectors and result in rough running.

  • Faulty fuel injectors: Worn-out Cummins diesel fuel injectors can cause return flow, decreased fuel pressure, and rough running.

  • Air intake restriction: A restricted air intake, often caused by dirty air cleaners, blocked pipes, or faulty airflow sensors, can lead to rough running or engine shutdown.

Lack of Power

If your Cummins diesel engine struggles with acceleration or starting, it may be experiencing a lack of power. Common causes include:

  • Dirty fuel filters: Clogged fuel filters can lead to power issues by creating a vacuum in the fuel supply.

  • Loose throttle linkage: Proper throttle cable tension is crucial for engine performance. A loose connection can result in reduced power.

  • Restricted air intake: A blocked air intake system can prevent the engine from achieving its full power potential, leading to symptoms like smoke from the exhaust.

  • Faulty fuel injectors: Faulty injectors can cause return flow, decreased fuel pressure, and starting problems, affecting power output.

If fuel-related issues are the cause, consider replacing worn or damaged components with genuine Cummins parts.

Black Smoke

When you see black smoke emanating from your Cummins diesel engine, it typically indicates an imbalance in the air-to-fuel ratio. Possible causes include:

  • Faulty fuel injectors: Cummins injectors that aren’t working correctly can cause a drop in fuel pressure, resulting in black smoke.

  • Faulty injector pumps: Pump issues can affect fuel pressure and injectors, potentially leading to black smoke. It’s essential to address problems with the injector and fuel systems promptly.

  • Dirty air cleaner: An insufficient supply of air in relation to fuel can produce black smoke. Check for restrictions in the air intake system, such as clogged pipes and dirty filters.

  • Faulty intercooler or turbocharger: Problems with these components can lead to smoke production. Variable vane turbo issues can also contribute to black smoke.

If black smoke persists, it’s crucial to investigate the air and fuel systems and perform necessary cleaning or part replacement.

White Smoke

White smoke from your Cummins diesel engine suggests improper fuel combustion. Potential causes include:

  • Engine and pump timing issues: Fuel pumps suffering from fuel starvation may experience timing problems, leading to incorrect burning.

  • Low engine compression: Low compression results in insufficient heat generation, causing fuel to burn improperly. Perform a cold engine compression test to check pressure levels.

  • Water or oil in the fuel: Clean fuel is essential for proper combustion. Any contamination, such as water or oil, can prevent fuel from burning correctly.

When dealing with white smoke, start by inspecting the fuel supply, pumps, and pressure levels.

Blue Smoke

If your Cummins diesel engine emits blue-tinted smoke, it’s likely burning oil along with diesel fuel. Possible causes include:

  • Worn piston rings or cylinders: Wear and tear over time can lead to oil leaks, resulting in blue smoke.

  • Faulty valves or stem seals: Similar to piston issues, worn valves, seals, pistons, or cylinders can allow oil to leak and cause blue smoke.

  • Over-filling the engine oil reservoir: Excessive oil can burn along with the fuel, producing blue smoke.

  • Faulty lift pump or injector pump: Malfunctioning pumps can introduce engine oil into the diesel fuel, leading to blue smoke.

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