Case Study

Resolving a Mysterious No Start or Stall Issue on a Golf

This case study highlights a perplexing issue we encountered while working on a customers 2011 Volkswagen Golf GTI.

The vehicle exhibited a random no start or stall problem, which presented a significant challenge for diagnosis. Through a systematic approach and thorough investigation, the root cause was identified as a malfunctioning high-pressure fuel pump in addition to other variables that where found the deeper we diagnosed the car. This case study outlines the steps taken to diagnose and resolve the issue, providing valuable insights for future troubleshooting scenarios.


The owner reported experiencing intermittent no start or stall issues, which occurred very randomly, weeks if not months apart and without any apparent pattern. The symptoms were challenging to replicate, making it difficult to isolate the cause.

The vehicle had already been taken to multiple mechanics prior to the the customer brining it to us. Despite these previous attempts, the issue remained unresolved. This aspect emphasizes the complexity of the problem and the challenge it presented.


We began by conducting a visual inspection of the vehicle’s electrical components, making sure that the wiring, coils, spark plugs, and any fuses, relays related to the fuel system were sound. in addition to that we also did a compression test and leak down test to ensure that the engines health is in good standing. 

Next was the fuel system, checking for any visible signs of damage or leaks with the fuel lines, low pressure fueling system, high pressure fuel system, & injectors. No obvious issues were detected right away, suggesting that a deeper investigation was necessary.

Our next step was to log important data about fueling and electrical to try and find any abnormalities that might come up, this included weeks of driving the car to be able to make sure that the intermittent issue would come up.


As per Volkswagen diagnostics documentation, after driving the car, and shutting it off, if the pressure on the high pressure fuel rail starts rising from 40 to 60 BAR with in a 5 minute period, this means that the injectors and rail in question are able to hold the pressure, in some very rare instances, this was not the case, as we experienced a drop in pressure within the fuel rail leading us to dig deeper into the fuel injectors, even though they where recently serviced and showed no signs of leakage.

After removing the injectors, we found that the service that was done to them was subpar at best, and the Teflon seals that are a mandatory Replacement whenever the injectors are service were not replaced leading to a very loose fitting injectors within the head galley.

We also went ahead and removed the high pressure fuel pump for further inspection as we suspected that fuel was being mixed in with the engine oil because of a failing pump piston seal which proved to be true, as the oil had a distinct smell of fuel.


After performing thorough diagnostics on the vehicle, our assessment led us to recommend two essential actions: replacing the High-Pressure Fuel Pump (HPFP) and also replacing the injectors, while also considering the replacement of the seals.

The HPFP is a critical component responsible for maintaining proper fuel pressure within the engine. If it malfunctions or becomes worn out, it can lead to issues such as intermittent stalling or difficulties in starting the engine. By recommending its replacement, we aimed to address any underlying problems related to the fuel delivery system.

Additionally, we advised the customer in replacing the injectors as part of our diagnostic findings. Over time, injectors can accumulate deposits or wear out, impacting their performance and potentially causing starting issues or engine misfires. Replacing the injectors was crucial to ensure their optimal functioning and prevent any future problems.

In our evaluation, we also took into account the condition of the seals associated with the HPFP and injectors. Seals play a vital role in maintaining fuel integrity and preventing leaks. If they are worn or damaged, they can compromise the overall performance of the fuel system. Therefore, considering the replacement of seals was an important aspect of our recommended actions.

Since we performed the diagnostics and implemented the recommended repairs, the customer has been driving the car for nearly six months without experiencing any recurrence of the previous intermittent stalling or starting issues. This extended period without any signs of trouble indicates that the recommended HPFP & injector replacement  were successful in resolving the root cause of the problem.

It is important to note that regular maintenance and monitoring of the vehicle’s performance are still essential to ensure continued reliability. However, the fact that the customer has been driving the car without any issues for such a considerable period demonstrates the effectiveness of our recommended actions in restoring the car’s performance and reliability.

Overall, our comprehensive diagnostics process, coupled with the recommended HPFP and injector replacement has resulted in a satisfied customer who has enjoyed trouble-free driving for almost six months.