Hi all, I wonder if anyone out there can help me, 12 months ago I bought my long suffering partner a stunning SLK 280 Edition 10, the car had only done 16K and has everything that she wants, the car is faultless in every way, well until about 6 weeks ago that is. Firstly I must apologise for making this so long but the more info you have then hopefully the better the chance of an answer to my problem. My partner drove to the supermarket and when she came out the car would not start, we had the usual choice words and then she called the AA, when they came out an hour or so later strangely enough it started, after her initial embarrassment the guy explained that it was relatively easy to flood the engine and cause this problem, she took his insult and drove off and the car ran like a dream as always, she stopped at another shop to get the things the last one never had and low and behold it wouldn't start again, this time she waited 4 hours for the AA as this was the 2nd time in the same day with the same fault so they said they'd recover it, now I met her at the scene and we tried several times in the 4 hours to start it, each time it would run for 1 sec and then stop, going on the last guys diagnosis of flooding I returned to my days in the eighties and floored the throttle and managed to get it to keep running but only idling and very lumpy, it eventually flashed up the management light and stalled, we continued to try every half hour or so until they arrived, he tried himself to no avail and plugged in his meter, the diagnosis was "Crankshaft Position Sensor" he lowered his body (truck body) got all set to winch it on flicked the key to take it out of park and it started like nothing was ever wrong!! of course we all laughed at this stage ...NOT !!! We drove home and arranged for MB to recover it under the Mobilo as it's still under used car warranty, they had it for a week replaced the sensor and said they'd deliver it home when they had a driver free, when it never arrived I called and they said they had the same problem when the car was in the valet bay so needed to take another look at it and of course I agreed, they came back and said that nothing else could be found so they would send off a sample of the fuel to get it analised, in the meantime I said that we might as well have it back as no faults were present anymore, the problem is that Mrs P refused to use it because it wasn't confirmed to be fixed so it sat on the drive with a full tank of fuel in it, I then in my wisdom said fine I'll use it for a while to prove to you it's ok. The car ran as it always had like a Rolex, never missed a beat or ran rough in any way shape or form, when I had used up all the fuel in it I went and filled it up, drove about 20 miles and stopped for a well earned pint, 1 hour later came out and guess what it wouldn't start, now I thought about it and left it for another hour and had a couple of not so deserved Diet Cokes, came back out again and it still wouldn't start, back were the AA again put on their box and up came the "Crankshaft Position Sensor again" he cleared the fault in the hope it may do just that and clear the fault but it didn't, now this is where it gets technical because this car had a full tank of fuel (only 20 miles used so there was nothing at all in the neck) I gave him the full history and that they wanted to analise the fuel last time so he took off the fuel cap and there was a considerable surge of pressure either sucking or blowing who knows but the strange thing is that with the cap off it started and immediately ran like the old Rolex as it always does, we left it running while the paperwork was done and when I went to get in it there was a very large puddle of fuel by the drivers door, when I looked under the car there was fuel running out of the drain tube which is situated at the top and is the overflow from the filler neck, I thought immediately how on this earth is fuel getting back up the neck and out of the tube when I must have used anything that was in that tube driving for the last 20 miles or so, now I'm thinking that the fuel tank must be getting pressurised to cause this. I drove it home and again Mobilo took it into MB, that was 2 weeks ago and they still have it there now!!! In the meantime of my last visit they have received back the fuel analysis report with indicates that the fuel contains water, 279parts / million to be precise, now the standards acceptable for distribution in the UK is actually 200parts / million so those extra 79parts seem pretty negligable to me and the fact that this car (when it does run) never misses a single beat and if you start throwing water into the cylinders any of the 6 I'm sure that I would notice, anyway to cut this now very long story short I agreed to allow their chief technician to use the car personally until it broke down on him and it duly has this week, twice to be precise and each time he has confirmed that there was no fuel pressure, so I would like to think that my problem was solved and they would drain out the tank replace the faulty pump and give the vehicle back, alas they will do that but won't do it under the warranty because the car contains contaminated fuel and any contamination will deem the warranty void, all this when there is a standard acceptance that water can be present in fuel each and everytime we buy it, not to mention what can be added after 3 years of condensation within the cars tank itself. The opinion is that if we drain out the tank and clear the system of this water the problem may just go away, If that were the case there would surely be some evidence when driving it that water was present in the running of the vehicle but like I keep saying it runs like a watch all of the time. I suppose my query is just how much damage could possibly be caused by such a small amount of water and why is the problem so intermittent, I feel that someone is lifting my leg here and I'm slowly loosing confidence in MB and there service standards. I'm sorry to have bored you all with this but hopefully someone out there has my answer. thanks for any responces they are most welcome. Ian.