It’s not common today to have bad fuel from the service station though it does happen. As a mobile mechanic we see a lot of breakdowns and bad fuel is generally not a major issue. What is an issue is E10 fuel (ethanol) being used, especially in older cars. We find the long term use of E10 fuel can be a catlyst to fuel system failures. Todays repair was a vehicle that was being run on E10. This fuel has been found to cause rust inside the fuel system, along with damaging rubber components, fuel pumps, pressure regulators and fuel injectors. One main reason this happens is that ethanol absorbs water, so when exposed to the atmosphere it will absorb moisture from the air. Once the ethanol has hit saturation point it will seperate leaving water in your fuel system. This, in the long term, will cause rust.
Todays vehicle was an AU falcon. The vehicle was running very rough and blowing a lot of black smoke. I found one injector blocked while another was dribbling fuel constantly. This was the main fault. The cause of this fault however was due to rust built up in the injector rail. This rust had damaged the injectors as well as the fuel pressure regulator.
I replaced the injectors and pressure regulator. The fuel rail was replaced with a good 2nd hand unit. New spark plugs were installed as the fuel issues had fouled the originals. Before fitting the new fuel filter, the fuel lines were flushed to ensure no more debris would cause further issues.
Once the repair was complete the engine ran 100%, a major improvement. A fuel treatment additive was added to the fuel to help process any contamination left in the tank.
The main pic shows a sample of the fuel removed from the fuel rail. When left to sit the rust will settle to the bottom. This is also a great example of why not to run your car down to the bottom of the tank as any sediment will be picked up and run through the fuel system.