5.9 Cummins Difficult Cold Start
What Causes Difficult Cold Starts in a 5.9L Cummins
There are several underlying causes of difficult cold starts in Cummins 5.9L engines.
Poor Fuel Quality and Gelling
If your engine is cranking slowly, failing to start or hesitating on ignition, it may be related to gelling. Any fuel, especially untreated or under-treaded can cause gelling and restricted fuel flow during winter. Cold start issues may also be due to low cetane, contaminants or water in the fuel. Cetane is important in diesel to improve cold starting. In addition, cetane increases the burn window for the fuel, resulting in more complete burn and power. This means you gain fuel efficiency and reduce soot entering the emissions system, resulting in fewer regens.Here’s how to fix a fuel quality issues:
- Add EDT+ Winter Defense at every fill-up to clean and improve fuel quality plus it adds for cold weather performance.
- Drain the contaminated fuel and replace it with a high-quality alternative.
Grid Heater Problems
Hard starts in cold weather may be due to grid heater problems. The grid heater may be problematic if your engine is cranking without ignition or is taking longer than usual to warm up. Grid heater issues could be caused by corroded battery cables reducing grid heater performance or a faulty grid heater that no longer heats intake air properly. Two solutions for this problem are:
- Checking the battery cables and terminals and clean them if corroded.
- Testing the grid heater and replace it if necessary.
Weak Battery or Electrical Issues
If your truck has difficulty starting when temperatures are below freezing or has a slow or weak crank, it might be due to a weak battery or electrical issue. If the problem is a weak battery, it won’t provide sufficient power to start in freezing weather. The problem may also be related to a faulty alternator or starter. Here’s how to address these issues:
- Test your battery’s voltage and replace it if it’s not holding a charge.
- Inspect your alternator and starter and repair or replace them if necessary.
Low-Quality or Thick Engine Oil
A hard start or sluggish engine is a sign of low-quality or thick engine oil, especially in cold temperatures. Using engine oil with the wrong viscosity, which isn’t suitable for cold weather, can hinder cranking. Switching to synthetic or low-viscosity diesel engine oil designed for low temperatures should fix the issue.
Air Intake or Fuel System Leaks
Along with difficulty starting, air intake and fuel system leaks can cause rough idling and poor acceleration. Here’s how to fix these problems:
- Inspect the fuel system and repair any leaks you detect.
- Examine the air filters and clean or replace them if clogged.
How to Diagnose Difficult 5.9L Cummins Cold Starts
Here are the best ways to diagnose cold starts.
Visual Inspection
Check for signs of fuel gelling, like waxy residue in fuel filters or the tank, which can restrict flow and hinder combustion. Inspect the battery cables and terminals for corrosion that weakens electrical connections. Also, examine air filters for dirt or clogs that restrict airflow. These issues are manageable with the right solutions:
- Treat the fuel system with an diesel emergency product like Diesel Winter Rescue, prevent with an anti-gel formula.
- Clean battery connections.
- Replace air filters if dirty.
Test the Grid Heater
Use a multimeter to test the grid heater’s functionality. If it doesn’t heat sufficiently during startup, remove and replace it.
Inspect the Fuel System
Check the entire fuel system for signs of air leaks, clogged fuel filters or water contamination in the fuel. If necessary, replace the fuel filter and repair leaks. You should also drain contaminated fuel and replace it with fuel treated with anti-gel.
Battery and Electrical System Test
Measure the battery’s voltage with a multimeter to check for cold start issues. Inspect the terminals and cables for corrosion, ensuring all connections are clean and secure. Test the starter and alternator to confirm they’re functioning correctly and replace or repair them if faulty.
How to Prevent Difficult Cold Starts in Cummins 5.9L Engines
Use our potent fuel additives to avoid Cummins cold start issues.
Hot Shot’s Secret Diesel Winter Anti-Gel
This advanced formula will help keep your diesel fuel flowing in freezing temperatures, preventing icing and gelling from causing hard starts. Hot Shot’s Secret Diesel EDT+ Winter Defense ensures reliable cold starts and adds lubricity to safeguard your vehicle’s injectors and fuel pumps from winter wear. Use a full dose with every tank during freezing weather to protect your engine and keep your truck running smoothly during even the coldest weather.
Hot Shot’s Secret Diesel Extreme
Hot Shot’s Secret Diesel Extreme cleans injectors, removes water and improves fuel quality, addressing fuel contamination that often causes difficult starts in winter. By adding it to your fuel tank, you can restore and maintain the efficiency of your fuel system, ensuring smoother starts and better performance. This powerful additive helps keep your engine running reliably during cold weather and year-round.
Start Your Engine Smoothly With Hot Shot’s Secret
Consider using Diesel Winter Anti-Gel or Diesel Extreme to support your engine in cold weather. While shopping, add EDT+ Winter Defense to your order for ongoing performance, even when the temperature drops.