Service function guideBad Fuel Diagnosis and Recovery

This Auto Veteran guide delivers a complete professional workflow for diagnosing and recovering from bad fuel, covering water intrusion, wrong-fuel fills and microbial or particulate contamination across petrol, diesel and flex-fuel vehicles. It is written for working mechanics and serious DIY owners who already understand basic fuel system layout and want a structured, evidence-based method rather than guesswork. You will learn how to confirm contamination with measurable tests, prepare the vehicle and workspace safely, execute a full drain-and-flush procedure, verify the repair with pressure and running checks, and apply the correct aftercare to prevent repeat failure. The guide also maps differences between common rail diesel, port injection petrol, direct injection petrol and hybrid systems so you can adapt the same logic to whatever rolls into the bay.