C250TD fuel starvation - please help!

dibbs851

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Please help. I bought a 1997 C-class 250TD about 8 months ago with 68,000 miles on it hoping that it would give me years of trouble-free motoring. Everything was fine until the weekend before last, when it suddenly lost power. The AA man came and took off the fuel filter, which was full of black contamination. So I paid £170 for a man to come along and empty the tank, assuming that this would solve the problem. After about 30 minutes there was no more fuel coming through, so the pump-out man put 10 litrs of fresh clean stuff in and that wouldn't pull through (well, it does, but it's a proper trickle!). Clearly there is a blockage / restriction somewhere - we tried pumping some diesel back to the tank from a jerry can under the bonnet using the AA man's syphon pump and it was as stiff as; it didn't want to flow at all. So..... the car is still running (I drove it back from Kent at the weekend), but it takes forever to get to 75 mph on the motorway and you get seen-off by cyclists at the traffic lights because it simply cannot draw enough fuel to get past 3,000 rpm. I have phoned a number of Mercedes 'specialists' today and nobody seems to be able to shed any light on this problem (apparently these cars never go wrong - apart from mine it would seem!). I don't know whether to just blow the fuel line back to the tank with an air line or carry-on chucking money at it - it seems my next option is to take the tank out which will cost about £400 I'm told, and still won't necessarily solve the problem. PLEASE help, this is doing my nut in! I knew I should have stuck with petrol :(.
 
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dibbs851

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Thanks Number Cruncher

Is this definitely the right fuel tank diagram for a 1997 C-class though? I thought it was much flatter and clearly made-up-of 2 sections?
 

Number_Cruncher

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Yes, I posted the wrong link 1st time round - it should be better now.
 
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dibbs851

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Thanks again. I'm not really sure what I'm looking at though (or looking for to be precise). I guess the top of these two is the tank as in my car, and if so do you know where the fuel is actually taken from? Is it just a strainer, is there a pump at the back, etc? It's not very clear from the pictures. I just need to know really whether I can blow the line clear from the front of the car back to the tank, or whether I need to take the tank out. Any ideas?
 

Number_Cruncher

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With the tank very low on fuel, take the strainer out and clean it.

Blowing back will, at best, give you a very temporary respite, and as soon as all the carp settles on the strainer again, you'll be back to square one.

At a guess, some idiot has been trying to run the car on chip fat or similar, instead of proper diesel from the pump.
 
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dibbs851

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Can you actually get to this strainer without removing the tank then? I'm a bit dubious about it being run on chip fat, as there was only one old boy owner before me and I've been running it on Tesco's diesel for the last 8 months since I bought it. I've spoken to the Tesco store where I last filled-up and they told me they shifted 13,000 litres of diesel through that pump on that day and haven't had any other complaints yet? And anyway, the fuel couldn't be THAT bad, could it? I can't help thinking something has rotted / given out - one of the pipes or something.
 
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dibbs851

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Heading home now (office PC) - hopefully all will become clear tomorrow. Thanks in advance.
 

Number_Cruncher

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Have a read of this thread;

http://forums.mercedesclub.org.uk/showthread.php?t=47695&highlight=strainer

Not your car, but, it is the same kind of strainer. They're remarkably similar in all the diesels.

The strainer is *much* more likely to be your problem than the pipes.

I don't know if you can get the strainer out easily or not. However, I would be surprised if it's too difficult.
 

simon_wall69

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There are other filters as well. If the strainer is fine, which it should be at your mileage, try sucking fuel through the lines at various points along the fuel line to pinpoint where the blockage is.
 

Number_Cruncher

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>>If the strainer is fine, which it should be at your mileage,

Judging from what the OP has said, particularly in the first post, I very much doubt that the tank strainer is fine (other than in terms of the density of its mesh!). If the main fuel pipe at the engine isn't flowing freely, then, you *know* it's something rearward of that.

I do agree though, once fuel is running freely, the pre-filter and secondary filter should also be changed.

If the OP is unlucky, he may need to clean the tank out as well.
 

simon_wall69

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I agree with what you say. But it does seem low mileage for the strainer to be clogged up.

If it is clogged up, which it probably is, then it should be investigated what has caused this.
 
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dibbs851

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Thankyou gentlemen for all your help and advice on this. I completely agree with you about the fact that I should work backwards from the filter to the tank; I just need to find-out what is along the way, i.e. where I might be able to split the pipe, is there a pump in the tank, etc. Can you shed any light on this for me? Do you know where I can get a decent image / diagram of the tank and the position of the strainer, as even my local Benz main dealer couldn't help me! Thanks again.
 

Number_Cruncher

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I wouldn't take the pipes apart - but, I would check for mechanical damage to the pipes. Has someone jacked the car up, and put the jack in a silly place, and crushed a pipe? This inspection is all really obvious, and shouldn't take more than 10 minutes.

The strainer, as per the piccie, is towards the upper rear of the tank - have a look, and see if you can find it.
 
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dibbs851

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Is that part # 53 / 56 in the top of the 2 pictures? If so, is this where the fuel is picked-up from on the way to the fuel filter, as it looks like it is single-ended? I assume that this strainer is to strain the fuel on the way out of the tank, and not on the way in (i.e. from the pump at the petrol station)?
 

Number_Cruncher

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Is that part # 53 / 56 in the top of the 2 pictures?

Yes

If so, is this where the fuel is picked-up from on the way to the fuel filter, as it looks like it is single-ended?

I don't know about the internal details of the tank, but, the location of these strainers bears little relationship to the inlets and outlets of the tank. On my W124, the strainer is under the centre of the tank - nowhere nea any of the inlets or outlets. You'll see how it works when you get it out.
 

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