BMW 118d 2004, 1.9 Diesel

Hi everyone,

I have one question coming from the very specific situation that happened.

Couple of days ago I went to gas station and guy that works there accidentally put 20 liters ( Half the fuel tank ) of gasoline instead of diesel ( My cars engine runs on diesel ). I didn't notice until I sat down and started driving home. Engine was very slow and weak. I was tired from work that day so I ignored the engine weakness with some stupid reason that it just happens sometimes. So in the morning I get in my car, place the key in and press the start button on which engine responds by trying to turn on but ( again, my guess ) it's too weak to turn on. I take the receipt from the gas station and see that the gas that I paid for was petrol. So I tried pressing start a couple of more times but I see that I am placing more strain on the engine than the actual help.

So, today I opened up the fuel tank and got out more than 19 liters of gasoline and refilled with 10 liters of diesel. I tried starting the car again but the same thing happens.

My guess is that gasoline is still left somewhere between the fuel tank and the engine and I am trying to get after that point so I can clean it and get out leftover gasoline. And hopefully engine will successfully run.

After watching a couple of videos, reading a couple of articles and taking a look at couple of diagrams I can see that the best solution might be to find fuel line closest to the engine, disconnect it and spill the gasoline into a different container.

Can someone answer If I am going in the right direction or not?

Thanks in advance.


For everyone that get the same problem in the future, I did the following:

I drained the fuel tank completely ( if possible lift the car up and pull the tank out which will allow you to clean it even better from debris and everything else that happens to be in your fuel tank ) then you will have to lift the car up to replace the fuel filter ( in this model, fuel filter is under the car ) and after that you can clean the closest fuel line to the engine together with injectors just in case. After that, put clean fuel tank back and fill your car with diesel.

My problem was that I cleaned the fuel tank, fuel lines and injectors without replacing the fuel filter under the car. Fuel filter was blocked by gasoline. Hope this helps.

  • Welcome to Motor Vehicle Maintenance & Repair! It sounds as though you are going in the right direction, however, the big thing you need to do is to remove everything in the fuel system, then re-add the diesel. You are only going to end up with a diesel/petrol mix, which isn't going to do you any good. Dec 4, 2022 at 22:39
  • Thanks @Paulster2! I understand. I think that maybe since I now have 10 liters of diesel and less than 1 liter of petrol in my tank it wouldn't effect the fuel system as much but I am not sure. Anyway, my current goal is as it says in the title to find the fuel line from which I can separate petrol from under the hood. Do you think you can help me with that? Thanks in advance Dec 4, 2022 at 22:44
  • Unfortunately I wouldn't even be able to tell you where to begin looking. I could probably find it, but only if I was there looking at it in person. My BMW knowledge is very limited as a brand. I'm sure it's under a mass of engine covers, but other than that I really couldn't tell you. Dec 4, 2022 at 23:27
  • From my research the main fuel line is marked with the blue color right beside the engine but I will have to verify that a bit better because my main goal is to clean that one. Thank you anyway @Pᴀᴜʟsᴛᴇʀ2 Dec 4, 2022 at 23:54

1 Answer 1


I don't know specifics about your engine, but diesel engines usually have a fairly large fuel filter. Your fuel filter has gasoline in it, so remove the fuel filter and spill the gasoline mixture out of it, then fill the filter with good diesel fuel and re-install the filter. The engine should then have diesel fuel immediately available for starting.

  • I understand. Honestly I think that's the only thing that is going to help me but I was honestly afraid of that answer since BMW decided to put fuel filter underneath the car so I have to lift the whole thing up. Thanks Dec 5, 2022 at 19:24
  • @szivkovicx That location -- at the fuel filter -- is where the fuel line comes closest to the engine. But as you know, even if you drain gasoline from the fuel line, there is still much more gasoline in the filter.
    – MTA
    Dec 5, 2022 at 20:59
  • Yeah you are right. Definitely I need to do an fuel filter replacement. Unfortunately I will not be able to do it myself even after I drained the fuel tank and cleaned everything else that I could because I can't lift the car up. I parked up in a space that's really bumpy so the only choice is to call towing service and mechanic. Dec 5, 2022 at 21:03

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