Understanding and diagnosing injection timing issues in a Volkswagen diesel van can be a complex process. This article delves into a real-world scenario of a user struggling with recurring problems after replacing injectors. We’ll explore potential causes and diagnostic strategies using VCDS (Vag-Com Diagnostic System).
The original poster, Jonesy, describes a persistent issue with his VW diesel van. After repeated injector replacements by a Delphi agent, the van runs smoothly for a short period (around 30km) before the problem resurfaces. The high cost of each injector (€500) underscores the need for accurate diagnosis before further replacements. Jonesy seeks confirmation of the injector’s fault before investing in another set.
Another user, Larimore, questions whether all injectors are faulty and suggests the possibility of cascading failures, where one malfunctioning injector triggers issues in others. He emphasizes the importance of using a Digital Storage Oscilloscope (DSO) to accurately diagnose individual injector performance. He points out that the injectors in question are Bosch, not Delphi. Furthermore, he highlights a critical observation from the VCDS data: low fuel pressure during cranking (rising from 0kpa to only 100kpa). This low pressure, significantly below the expected range (around 4700 kpa for a similar Cummins engine), raises concerns about the fuel system’s ability to deliver sufficient fuel for combustion. Larimore speculates about potential causes, such as a faulty fuel pump, a problem with the high-pressure rail, or even the ECU shutting off fuel delivery.
While the initial suspicion falls on the injectors, the low fuel pressure reading suggests a broader problem within the fuel system. Using VCDS to analyze injection timing and fuel pressure data is crucial for pinpointing the root cause. Further investigation using a DSO to examine individual injector waveforms could provide a more granular understanding of injector performance. Addressing the low fuel pressure issue is paramount, as it directly impacts engine performance and could potentially damage components. Possible solutions include checking for fuel leaks, inspecting the fuel pump, and verifying the integrity of the high-pressure fuel system.
Ultimately, resolving this issue requires a systematic approach, combining VCDS diagnostics with a thorough understanding of diesel engine operation. Analyzing live data, including injection timing and fuel pressure readings, is essential for accurate diagnosis and effective repair. Further investigation into the low fuel pressure is necessary before considering additional injector replacements.
