Mercedes Vaneo hot start problem

Swifters

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Hi all, I have a mercedes vaneo which is progressively getting worse on hot start. Fine on cold start. I replaced the fuel filter a couple of months back and then a couple of weeks later the fuel pump packed up so that has been replaced too. All been fine until the last couple of days. I did have a renault :( at one point with a similiar probelm, there was a TDC sensor that I cleaned up and it ran fine afterwards, Im not sure if its a sensor problem or a fuel problem? All injectors have been replaced with genuine mercedes ones about a year ago/6000 miles ago.
 

mattkh

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What mileage?
Also, petrol or diesel?
 

alexanderfoti

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Camshaft position sensors typically tend to fail when hot then start working again when cooled down. It can be checked with a diagnostic tool to see if you have cam/crank sync
 
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Ok thank you. Seeing as you are not far from me I will pop it into you. Would tomorrow morning be ok?
 

alexanderfoti

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Ok thank you. Seeing as you are not far from me I will pop it into you. Would tomorrow morning be ok?

I'm fully booked for tomorrow at the moment. Saturday or Monday would be better if you can make it then?
 
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Swifters

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I had the cam and crank sensors tested on friday, no problem with those. I have replaced the spark plugs today but the problem is still there. It is starting to be a bit difficult to start when cold now too. I suspect it could be a fuel supply problem. One of the injectors packed up last year, so I thought it wise to replace the fuel filter this year. However, since then the fuel pump packed up and now this bad starting, especially when hot. Ive checked the fuel filter to see if one of the four pipes was connected incorrectly or the direction of the flow was wrong, but it all seems ok as the arrow is in the right direction and the pipes have different diameters so I cant see how they could have been connected back incorrrectly. Do the charcoal filters give problems? I suspect it is a fuel problem because I had to press the accelerator pedal to get it going today plus there is the occasional strong smell of fuel when it has been troublesome starting. Perhaps there is a choke problem or a starter motor problem?
 

alexanderfoti

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If the pipes were connected incorrectly it would not run at all.

Strong smell of unburnt fuel suggests ignition side fault as you would smell fuel if there was no fuel getting to the engine. It needs basics such as fuel pressure and fault codes read really...
 
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Swifters

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ok, I will try and get it to you next week sometime. Would saturday be ok? Ive been filling up at Costco recently so wonder if it could be something to do with the fuel or perhaps just coincidence
 

alexanderfoti

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Yes no problem, just let me know on the morning what time you plan on coming.

Its unlikely to be fuel unless you filled it with diesel but it would have stopped completely if that was the case!
 

Steve@Avantgarde

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So I take it cranks over, but doesnt fire into life? If you suspect a fuel problem, have you checked the fuel pressure? You will need a gauge to do this, spec is 3.8-4.2 bar.
 
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Swifters

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I am almost certain it is the map sensor. I soaked it in wd40 and cleaned the housing it goes into with a cotton bud (it was a bit oily/grubby) and it is SO much better, I think a new sensor would probably cure it completely but Ill see. thanks for everyones help.
 

alexanderfoti

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I am almost certain it is the map sensor. I soaked it in wd40 and cleaned the housing it goes into with a cotton bud (it was a bit oily/grubby) and it is SO much better, I think a new sensor would probably cure it completely but Ill see. thanks for everyones help.

Shame it didnt play up before! Glad you identified the cause.
 

mattkh

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I am almost certain it is the map sensor. I soaked it in wd40 and cleaned the housing it goes into with a cotton bud (it was a bit oily/grubby) and it is SO much better,
Thank you for the feedback.
Your engine is the same as in my A class w168. Can you please tell me where is this MAP sensor that you soaked.
 

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