March 2020

MARCH 2020 AFTERMARKET 31 EYEBROW www.aftermarketonline.net vanes inside the turbocharger to increase or decrease boost pressure. (fig. 1). Knowing now the system design, and that said system needs vacuum to operate, we can continue. From personal experience, on most systems the actuator arm on the turbo should move on engine start-up, so a quick visual check of this could give good direction. Another would be to monitor boost pressure sensor plausibility with ignition on, then engine running to see if it is reading correctly and possibly even use a pressure pump to verify accuracy of the sensor. Our next test would be to check the condition of the actuator diaphragm as this is a common failure on the VAG engines. After that we would check the vacuum supply to control solenoid and actuator. Accuracy As this vehicle had so many new parts fitted I decided firstly to verify the accuracy of the new boost pressure sensor fitted just as a quick check to confirm its plausibility. My readings from the road test were accurate. My main concern was that it was an aftermarket part, and experience has proved that sometimes they do not always operate as accurately as an OE part. Using a pressure pump to apply different pressures to the sensor and monitoring live data it was indeed accurate. While viewing live data, I decided to view other serial data relating to the new parts in order to rule out any issues. All appeared to be fine. I then changed the pressure pump into a vacuum pump and tested the turbo actuator diaphragm on the new turbo. This test confirmed the diaphragm held vacuum. This isn’t normally the route I would take, but on this vehicle, I wanted to make sure everything was good before proceeding too far and to be fair only takes a matter of minutes to confirm provided access is good. I then decided to test vacuum supply to the control solenoid because if we having nothing in then we will certainly have nothing out. Nothing On testing supply from the vacuum pump there was nothing at all, so I had found my issue (fig.2). Visually inspecting the vacuum pump found a plastic T-piece outlet. One feed supplies the brake servo, and the other smaller outlet feeds the boost control solenoid. As the brakes felt good on my road test and the customer had no complaints of braking issues I felt fairly confident the vacuum pump itself was working and testing the outlet from the pump with a gauge confirmed it. I then knew I had either an outlet issue to turbo or possibly a blocked pipe. Upon removing the plastic outlet and inspecting I found that the smaller pipe was blocked solid with carbon/dirt. I then cleaned the outlet and refitted the part and performed my vacuum test to the solenoid again and this time I had good healthy vacuum. (fig.3.). Repaired and ready Reassembling the vehicle and retesting the system showed the actuator arm on the turbo now moved on start-up and increasing the engine revs in the workshop showed the turbo to create boost. A lengthy road test monitoring data confirmed the system now operated correctly and full power had been restored with no faults codes stored. The customer was then contacted and notified that the vehicle was repaired and ready for collection. On speaking to the customer, he thanked me for all of my help and could not believe I had fixed his issue in the hour we had agreed. He asked me how I had done it and I explained how knowing how the system worked allowed me to carry out accurate tests to quickly find the cause without wasting time or money. As the saying goes, ‘if you don’t know how it works, how can you fix it?’ If you don’t know how it works, how can you fix it? ” Fig. 2 Fig. 3