Dodge Ram Exhaust Color Diagnosis: White Smoke Blue Black

A small amount of visible smoke emitting from an engine’s exhaust system can be considered normal at times for all Dodge Ram 5.9L Cummins diesel powered engines. But excessive smoke can be a sign of more serious mechanical problems.

NOTE: This troubleshooting guide applies to the Dodge Ram 5.9L diesel engines manufactured between 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007.

Diagnosing excessive exhaust smoke starts with an examination of the symptoms, including the burning smell or smoke color. Use the following troubleshooting guide to trace and correct faults if the Dodge Ram 5.9 liter Cummins is blowing excessive amounts of black, blue or white smoke from the exhaust’s tailpipe.


  • Cause: Check for raw fuel in the intake manifold. 
  • Correction: Inspect fuel injectors for leakage. Perform a fuel injector test. 
  • Cause: Static timing not in accordance with factory specifications.
  • Correction: A diagnostic trouble code would have been triggered. Use a diagnostics mobile scan tool to pull code(s) and refer to powertrain diagnostic procedures.
  • Cause: Turbocharger air intake restrictions.
  • Correction: Remove any air restrictions.
  • Cause: Check for excess build up on turbocharger compressor wheel or the diffuser vanes.
  • Correction: Refer to turbocharger cleaning procedures. 


  • Cause: Inspect the valve seals to see whether or not they are incorrectly installed, worn, or brittle.
  • Correction: Replace valve the valve stem oil seals.
  • Cause: Inspect for worn valve guides or valve stems.
  • Correction: Remove valves and check the guides and valves. Replace if necessary.
  • Cause: Incorrectly installed or broken piston rings.
  • Correction: Tear down engine and perform inspection of piston rings.
  • Cause: Piston ring end gap out of spec.
  • Correction: Extract piston and use a thickness gauge to measure piston ring end gap.
  • Cause: Excessive taper and cylinder bore wear.
  • Correction: Remove pistons and measure taper and cylinder bore wear.
  • Cause: Cylinder damage.
  • Correction: Extract pistons and perform inspection of cylinder bore for porosity or cracks. If possible, repair with a cylinder liner.
  • Cause: Piston damage.
  • Correction: Extract pistons and check for holes or cracks. Measure taper and piston for out-of-round.


  • Cause: Fuel injector not seated correctly.
  • Correction: Inspect washer (shim) for proper thickness. It’s located at the bottom of fuel injector.
  • Cause: Malfunctioning fuel injection pump.
  • Correction: A diagnostic trouble code would have been triggered. Pull engine code with a diagnostic scan tool. Refer to powertrain diagnostic procedures for more information.
  • Cause: Fuel supply side restriction to transfer pump.
  • Correction: Check fuel transfer pump pressure. Test fuel transfer pump.
  • Cause: Malfunction occurring with the fuel transfer (lift) pump.
  • Correction: A diagnostic trouble code would have been triggered. Refer to powertrain diagnostic procedures in service manual.
  • Cause: Incorrect intake/exhaust valve adjustment, possibly too tight.
  • Correction: Refer to standard procedures for exhaust valve and seats in service manual.
  • Cause: Malfunctioning intake manifold air temperature sensor.
  • Correction: A diagnostic trouble code would have been triggered (check engine light). Use a diagnostic scan tool to pull trouble codes.
  • Cause: During cold weather the intake manifold heater elements are not working properly.
  • Correction: Refer to factory service manual under NTC test in powertrain diagnostic procedures. It should be noted, a malfunctioning heater element will not trigger a diagnostic trouble code.
  • Cause: Possible internal engine damage, such as a scuffed cylinder.
  • Correction: Carefully inspect engine oil and oil filter for signs of damage, such as excessive metal particles.
  • Cause: Restriction existing in fuel supply side of fuel system.
  • Correction: Test fuel transfer pump pressure. Refer to factory service manual for testing procedures.
  • Cause: Static timing incorrect.
  • Correction: Improper static timing will trigger a diagnostic trouble code (DTC). Use diagnostic scan tool to pull trouble codes.
  • Cause: Air in fuel supply. Inspect fuel supply side for leakage (the area between fuel tank module and transfer pump).
  • Correction: Refer to fuel system and fuel transfer pump testing and diagnosis and factory repair manual.
  • Cause: Possibly coolant leaking into the engine’s combustion chamber.
  • Correction: Perform a pressure test of the coolant system.
  • Cause: DTC’s active or multiple, intermittent diagnostic trouble codes.
  • Correction: Use diagnostic trouble scan tool to pull codes. Refer to powertrain diagnostic procedures information in factory service manual.
  • Cause: Engine block heater is not working correctly during very cold ambient temperatures. Note, not all models are equipped with a engine block heater.
  • Correction: Remove and replace engine block heater. 
  • Cause: Engine coolant temperature sensors not working properly.
  • Correction: Check thermostat for correct operation. Also, a diagnostic trouble code will have been triggered. See factory service manual for diagnostic service procedures.
  • Cause: Engine Control Module (ECM) improperly calibrated or not calibrated.
  • Correction: This will trigger a diagnostic trouble code. Use a diagnostic scan tool to pull trouble codes.
  • Cause: Fuel filter blockage.
  • Correction: Perform a fuel pressure drop test. Also refer to fuel transfer pump testing and diagnostic procedures in factory service manual.
  • Cause: Bad fuel, incorrect fuel grade or poor quality fuel.
  • Correction: Temporarily switch to a different fuel brand and note any changes in performance. If noticeable differences are seen, change brand.
  • Cause: Fuel heater temp sensor or fuel heater is not working correctly. This will also cause a waxy build-up in the fuel filter.
  • Correction: Test fuel heater. Refer to fuel heater testing and diagnosis in repair manual.
  • Cause: Fuel injector hold-downs are lose.
  • Correction: Torque to factory specifications.
  • Cause: Fuel injector not working properly.
  • Correction: A faulty fuel injector will trigger a trouble code. Perform a cylinder balance test using DRB scan tool to isolate individual cylinders. It should be noted that the DRB scan tool is privileged to dealers only.
  • Cause: Cracked or warped cylinder head. Damaged head gasket resulting from overheating. Cracked engine block.
  • Correction: Perform leak down test and compression check.

Most Common Causes of White Exhaust Smoke

It’s not uncommon to see excessive white exhaust smoke upon starting a the Dodge Ram truck on cold days. This is often a result of steamed caused by condensation. If excessive white smoke is still present well after the vehicle has warmed. It would be a good idea to have the truck inspected for internal coolant leaks. It should be noted that burning coolant will have a sweet smell.

Most Common Causes of Blue Exhaust Smoke

It only takes a small amount of oil to leak into the cylinders and causes blue smoke to billow out of the tailpipe. The most common cause of blue exhaust smoke is when oil leaks past engine seals and mixes with fuel. This often happens to high mileage trucks with worn gaskets or seals.

When blue exhaust smoke is more pronounced upon start-up, this could be a sign of damaged valve guides or piston seals. Worn or damaged valve guides will often cause rattling noises too.

Most Common Causes of Black Exhaust Smoke

The most common reason why a Dodge Ram 5.9 liter Cummins engine will blow excessive black smoke is when the engine is burning too much fuel. This is especially true for modified trucks with custom ECU turning. On non-modified trucks, other common reasons might include a dirty air filter, faulty fuel-pressure regulator, intake sensors or fuel injectors.

It should be noted that most vehicles burning an excessive amount of black smoke will also experience poor fuel economy.

Auto Repair

Your friendly neighborhood online mechanic at your service! We are here to help you fix your automotive related problems—free. Have a question? Post it in the comment box, but please provide a detailed description of your issue. We will try and answer it ASAP.

Auto Repair has 35 posts and counting. See all posts by Auto Repair

2 thoughts on “Dodge Ram Exhaust Color Diagnosis: White Smoke Blue Black

  • August 9, 2016 at 7:26 am

    Some say black smoke is good and others say it’s bad. For example, black smoke in the diesel performance trucks is a good thing. Others say that black smoke is just unburned fuel, which means low power. So is black smoke good or bad?

    • August 9, 2016 at 7:36 am

      Black smoke on modified trucks is an indication that there isn’t a sufficient air to aid in fuel consumption. Unburned fuel can wash rings down and result in some lost power. But most high horsepower trucks belch some black smoke. Heck, some dyno tuners aren’t satisfied until they see black smoke pouring from the tailpipe.


Leave a Reply

Your email address will not be published. Required fields are marked *