There are many reasons why the engine won’t start. Among the most common culprits is the fuel system, particularly the diesel injectors. Diesel injectors are responsible for delivering the precise amount of fuel into the combustion chamber at the right time. Bad diesel injectors may cause an engine not to start or run terribly. Below is a step-by-step guide to help diagnose and resolve injector-related issues when the engine won’t start.
1. Check for Fuel Supply
It’s important to confirm that fuel is reaching the injectors. A lack of fuel could result from a clogged fuel filter, a faulty fuel pump, or an airlock in the fuel lines. To ensure proper fuel supply:
- Inspect the Fuel Tank: Verify that there is enough diesel in the tank. Sometimes, the problem can be as simple as running out of fuel.
- Check the Fuel Lines: Look for leaks, cracks, or disconnections in the fuel lines. Any interruption in the fuel supply can prevent the engine from starting.
- Test the Fuel Pump: If the fuel tank and lines are intact, the next step is to check the fuel pump. A malfunctioning pump won’t supply fuel to the injectors, which can cause starting issues.
2. Inspect Diesel Injector Visually
A visual check is a simple but necessary method of assessing diesel injectors. Though it will not yield a perfect diagnosis, it may help users discover some initial clues to the problem.
- Look for Leaks: Inspect the area around each injector to check if there is any fuel leakage. Leaking injectors can cause a variety of problems, including hard starting, rough idling, and engine misfire. If there is a noticeable fuel leak around the injectors, it may need to be replaced or reseated.
- Check Injector Wiring and Connectors: Diesel injectors are controlled by the engine’s electronic control unit (ECU), so it’s essential to ensure that the wiring and connectors are intact. Damaged and corroded wires could prevent the injectors from functioning correctly.
3. Test Injector Resistance
A quick way to check whether a diesel injector is functioning properly is to measure its resistance using a multimeter, for the resistance value can indicate whether the injector coil is damaged or if there is an issue with the electrical circuit.
- Set the Multimeter: Set the multimeter to measure resistance.
- Measure the Resistance: Connect the multimeter probes to the terminals of the injector. Compare the reading to the manufacturer’s recommended resistance value.
- Interpret the Results: If the reading is too high or infinite, the injector coil is likely faulty. A low or zero resistance reading suggests a short circuit.
4. Test Injector Nozzle Spray Pattern
The spray pattern is an important part of the injector’s performance. Diesel injectors are designed to atomize the fuel into a fine mist to combust efficiently. A clogged or malfunctioning injector can disrupt the spray pattern, which prevents the engine from starting or causes a rough idle.
To check the spray pattern:
- Use an Injector Tester: If possible, use an injector tester to check the spray pattern outside of the engine. This tool simulates the engine’s pressure and shows how the injector is delivering fuel. If the fuel is being delivered in large droplets or not spraying evenly, the injector may be clogged or faulty.
- Examine the Spray: The spray should be a fine mist in a uniform cone pattern. Any irregularities suggest that the injector is not performing properly.
5. Check Injector Timing and Synchronization
In some cases, injector timing may be misaligned, leading to improper combustion. Diesel engines rely on precise timing for optimal performance, so even slight discrepancies can lead to starting issues.
- Verify Timing with Diagnostic Equipment: Advanced diagnostic tools, like a scan tool or diagnostic software, can help check if the injectors are synchronized with the engine’s timing. These tools are especially useful for modern common rail systems that control injectors electronically.
- Adjust the Timing: If timing is found to be off, it may need to be corrected by using the diagnostic tool or a professional mechanic. This step often requires specialized knowledge and tools.
6. Check for Fault Codes and ECU Issues
If the engine still won’t start after inspecting and testing the injectors, it’s essential to check for any stored fault codes in the engine’s ECU. Now, diesel engines are equipped with sensors that can detect injector malfunctions and other fuel system issues.
- Use a Diagnostic Scanner: Plug a diagnostic scanner into the engine’s OBD-II (On-Board Diagnostics) port and check for any fault codes related to the injectors.
- Clear and Test Again: If fault codes are present, addressing the underlying issue should restore injector functionality. Clear the codes and attempt to start the engine again.
7. Consider Professional Help
If the above steps are not able to fix the problem, or the problems with the injectors fall beyond the DIY diagnostic capability, it is best to seek professional help. Because diesel fuel injectors are precision equipment and their diagnosis and testing require professional knowledge and equipment, a professional diesel technician can test the injector in realistic conditions and can perform complex procedures such as ultrasonic cleaning or injector calibration.
When a diesel engine won’t start, one of the important parts of diagnosing would involve the injector. Fuel supply checks, visual checks, resistance tests, spray pattern analysis, and ECU diagnostics provide important insights into injector performance. The careful following of all these steps can help the users identify injector problems. However, more complex problems may call for the opinion of a professional to avoid unnecessary repairs to ensure the best performance of the engines.
