Smart Forfour Fuel System Woes: Stalling and Power Loss

As a DIY enthusiast with some repair experience, I had a very similar issue with my Smart Fortwo diesel (2006). The symptoms you describe match exactly what I experienced, check engine light, stalling, and power issues. Initially thought it was the fuel pressure regulator, but after taking it to my regular workshop, they discovered it was actually related to a recent fuel filter change. The fuel system was showing incorrect pressure readings because the system needed proper bleeding after the filter replacement. The fix involved: Complete diagnostic scan, Fuel system pressure test, Bleeding the fuel system properly, Clearing error codes Total cost was 45€ and resolved all symptoms. The check engine light stopped appearing and power was fully restored. Before suggesting more specific solutions, could you provide: Current mileage, When was your last fuel filter change, Are you getting any specific error codes, Does the problem occur more during cold starts This would help determine if your fuel rail pressure sensor or fuel regulator actually needs replacement, or if its just a simpler fix like in my case. Worth noting that these fuel system issues often appear similar, but proper diagnosis is crucial to avoid replacing parts unnecessarily.

Thanks for sharing your experience. My latest service was done 3 weeks ago at 113022 KM. The symptoms definitely match what you described. I can add that the rough idle gets worse when the engine is cold, and the engine misfire becomes noticeable especially during acceleration. The fuel pump makes an unusual whining noise too. During the last service they did change the fuel filter, so your suggestion about bleeding the system properly makes a lot of sense. The error code reader shows P0087 which points to low fuel rail pressure. Maybe I should have the workshop check the fuel system pressure and properly bleed it before replacing any expensive parts.

Thanks for providing those additional details. Your situation sounds even more similar to what I experienced, especially with that P0087 code and symptoms appearing after a recent service. The whining fuel pump and rough idle during cold starts, combined with the engine misfire during acceleration, match exactly what my Smart was doing. Since you mention the recent fuel filter change, I am now almost certain you are dealing with the same issue I had. The low fuel rail pressure indicated by the P0087 code often triggers when air is trapped in the system. In my case, the pressure sensor readings were off because of air pockets in the fuel lines, not because of a faulty regulator. Quick tip from my experience: before investing in a new pressure sensor or fuel pressure regulator, definitely have them: Perform a complete fuel system bleeding procedure, Test the fuel rail pressure with proper diagnostic equipment, Check all fuel line connections for potential air leaks, Clear the codes and test drive The whole procedure should cost significantly less than replacing parts. Mine ran perfectly after proper bleeding, saving me from an unnecessary parts replacement that would have cost around 300€.

Based on all this helpful information, I will proceed with having the workshop check the fuel system pressure and do a proper bleeding first. The whining pump sound and P0087 code really seem to match your experience exactly, and since my problems also started after the recent service with fuel filter change, it makes perfect sense. Will schedule an appointment to check the fuel rail pressure and have them do a complete system bleed before considering any expensive parts replacements. It is reassuring to know this might be resolved without major repairs, especially since my symptoms match yours so closely, from the cold start issues to the misfiring during acceleration. I will update the thread once I get the pressure readings and bleeding done. Hoping for the same positive outcome you had with restored fuel efficiency and no more check engine lights. Makes sense to try the 45€ fix before jumping into replacing the fuel pressure regulator or other components.