1990 Mack EM-6 Injector Pump Troubleshooting and Repair

[MikePhua]

The 1990 Mack EM-6 engine, a part of the Mack truck series, is known for its durability and reliability in demanding work environments. However, like all complex machinery, it may face issues over time, particularly with components such as the injector pump. Injector pump problems can cause a host of engine performance issues, including poor fuel delivery, engine misfires, and decreased fuel efficiency. Understanding the causes and solutions for these issues can save operators time and money while keeping their Mack truck in optimal working condition.
Symptoms of Injector Pump Problems
When the injector pump fails or malfunctions, there are several noticeable symptoms that can help diagnose the problem:

1. Hard Starting: If the injector pump is failing, it may struggle to deliver the proper amount of fuel to the injectors, causing the engine to be difficult to start, especially in cold weather.
   
2. Rough Idle: A malfunctioning injector pump can result in irregular fuel delivery, causing the engine to idle roughly or unevenly.
   
3. Excessive Smoke: An improper fuel mixture due to a faulty injector pump can result in excess smoke, particularly black smoke, indicating incomplete combustion.
   
4. Poor Fuel Economy: The injector pump is responsible for delivering the correct amount of fuel to the engine. If it is not functioning properly, fuel efficiency can drop significantly, as too much or too little fuel is injected.
   
5. Engine Misfires: If the fuel is not being delivered to the injectors at the correct pressure, misfires may occur. This can affect the overall performance of the engine and make it feel sluggish.
   
6. Stalling: A serious issue with the injector pump may cause the engine to stall, especially when under load or during acceleration.
   

Common Causes of Injector Pump Failure
Several factors can lead to injector pump issues in the Mack EM-6 engine. Identifying the cause is the first step in troubleshooting and repairing the problem.

1. Contaminated Fuel: One of the leading causes of injector pump failure is contaminated fuel. Dirt, water, or debris can enter the fuel system and clog the filters, injectors, or the pump itself, reducing fuel flow and causing the pump to malfunction.
   
2. Worn Pump Components: Over time, the internal components of the injector pump, such as seals, bearings, and springs, can wear out. This wear can cause the pump to lose its precision and ability to deliver fuel at the correct pressure.
   
3. Fuel Delivery Issues: A failing fuel filter or fuel lines that are clogged or leaking can lead to inadequate fuel delivery to the pump, causing it to operate inefficiently. This can result in poor engine performance.
   
4. Improper Fuel Timing: Fuel timing is crucial for proper engine operation. If the timing of the injector pump is off, it can cause poor fuel combustion and engine misfires.
   
5. Electrical Problems: The electronic control of the injector pump, if equipped with an electronic governor or control unit, may fail due to wiring issues, faulty sensors, or electrical component failure.
   
6. Air in the Fuel System: Air trapped in the fuel lines or injector pump can lead to poor fuel delivery. This can occur if there is a leak in the fuel system or if the fuel tank is low, allowing air to enter.
   

Troubleshooting and Diagnosis
To diagnose the problem with the injector pump on a 1990 Mack EM-6, you will need to perform a few key steps. Here is a step-by-step guide to troubleshooting injector pump issues:

1. Check for Fuel Contamination: Inspect the fuel tank and fuel filters for signs of water or debris. Replace the fuel filter and clean the fuel lines if necessary. If the fuel is contaminated, it should be drained and replaced.
   
2. Inspect the Injector Pump for Leaks: Check the injector pump for any visible leaks. A leaking pump can cause a loss of fuel pressure, resulting in poor engine performance. If leaks are found, the pump may need to be resealed or replaced.
   
3. Examine Fuel Pressure: Use a fuel pressure gauge to check the fuel pressure at the injector pump. If the pressure is too low, it could indicate a problem with the fuel pump, fuel lines, or filter.
   
4. Verify the Fuel Timing: Incorrect fuel timing can lead to poor engine performance and misfires. Use a timing light or diagnostic equipment to check the timing and adjust it if necessary.
   
5. Test Electrical Components: For electronically controlled injector pumps, inspect the wiring, sensors, and control unit for faults. Use a multimeter to check for continuity and ensure proper operation of the electrical components.
   
6. Check for Air in the Fuel System: Bleed the fuel system to remove any air pockets. Ensure that all fuel lines and connections are properly sealed to prevent air from entering the system.
   
7. Perform an Injector Test: If the injector pump appears to be functioning but the engine is still misfiring, test the injectors. Clogged or faulty injectors can prevent proper fuel delivery, even if the pump is working correctly.
   

Repairing or Replacing the Injector Pump
Once the root cause of the injector pump problem has been identified, you can decide whether to repair or replace the pump. Here are the common approaches to resolving injector pump issues:

1. Cleaning and Servicing: If the pump is clogged or has minor issues such as worn seals or gaskets, it can often be cleaned and serviced. This involves disassembling the pump, cleaning the internal components, and replacing any worn-out parts. However, this requires expertise, as improper reassembly can cause further damage.
   
2. Rebuilding the Injector Pump: For more severe wear or damage, a complete rebuild may be necessary. Rebuilding an injector pump involves replacing internal components such as the rotor, camshaft, and springs. This process is typically performed by professional technicians or specialized repair shops.
   
3. Replacing the Injector Pump: If the pump is severely damaged or cannot be rebuilt, replacing it with a new or remanufactured injector pump may be the best option. While this can be costly, it ensures that the pump operates at full capacity and restores the engine’s performance.
   

Preventative Maintenance Tips
To prevent future issues with the injector pump and keep your Mack EM-6 engine running smoothly, regular maintenance is essential. Here are some preventative tips:

1. Use Clean Fuel: Always use high-quality, clean fuel to prevent contamination that can damage the injector pump. Regularly change the fuel filter to prevent dirt and debris from entering the system.
   
2. Monitor Fuel Pressure: Check the fuel pressure regularly to ensure the injector pump is receiving the correct amount of fuel. Low pressure can indicate issues with the pump or fuel delivery system.
   
3. Regularly Inspect the Fuel System: Inspect the fuel lines, injectors, and pump for any signs of wear or leaks. Addressing small issues early can prevent more severe problems down the road.
   
4. Keep the Fuel System Air-Free: Ensure that the fuel system is free from air pockets by regularly bleeding the system. Air in the fuel can lead to poor engine performance.
   
5. Service the Injector Pump Regularly: Schedule regular service for the injector pump to keep it in good working condition. A professional inspection can help catch potential issues before they cause damage.
   

Conclusion
Injector pump issues in the 1990 Mack EM-6 engine can cause significant performance problems, but with the right diagnostic steps and repairs, these issues can be resolved. Regular maintenance, including fuel system checks and proper servicing, can help extend the lifespan of the injector pump and keep the engine running smoothly. By understanding the causes of injector pump failure and knowing how to troubleshoot effectively, Mack truck owners can maintain their equipment and avoid costly repairs.