C200k (2001) Starting Problems

nebulaman

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C200k (2001)
Well I had to sell the C180 (1995) for a "family car" but now i'm back with a C200k (2001).

The car has developed a starting problem that is steadily getting worse. It cranks but doesn't start. At first it would only do this a couple of times before starting but now it takes 5-10 min to start. When it does start it will then cut out again. The fault only occurs when the car has stood overnight or a few hours (gradient doesnt matter). Heres what I have done to try and trace the fault.

Checked Battery - New 18 months ago.
Changed Key Fob Batteries - Still the same.
Unplugged MAF - Still have the problem.
Tried locking and unlocking the car several times incase of immobiliser fault - Nope.

In your opinion could it be one of the following?

- Starter Motor Relay fault (relay K)
- Starter Motor needs greasing (read this somewhere)
- Fuel Priming problem

When I turn the key (lego brick type) I can here some whirring from the engine bay which I think is the fuel pump. But it will only start if I hear a whirring from the rear of the car. Is there a second fuel pump in or near the fuel tank and this is where the problem lies? I just hope that if there is one, that it isn't inside the fuel tank as it would be more expenisve to replace! Is there a relay attributted to the fuel pump that i could change?

Any help or suggestions? Thank you in anticipation!
P.s. Still very much a rookie with a spanner so nothing to technical eh?
 

Ian B Walker

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300-24, saloon and coupe, E300 24 valve diesel estate
Check the filter on the return line to the tank. It has an electrical plug on the top of it. It is situated on the passengers side wing towards the front of the car. These sometimes fail and cause the problem you are exhibiting.
 
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nebulaman

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C200k (2001)
Check the filter on the return line to the tank. It has an electrical plug on the top of it. It is situated on the passengers side wing towards the front of the car. These sometimes fail and cause the problem you are exhibiting.
Thank you, I shall check it in the morning. Excuse my ignorance but is it just a case of unplugging the connector and trying, viewing the filter or try a replacement?
 
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Ian B Walker

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300-24, saloon and coupe, E300 24 valve diesel estate
It takes the fumes away to the tank. No petrol liquid present. Take it off the car and turn upside down. tap it and if you get charcoal particles, replace with a new one.
 

Alex Crow

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Hello again Richard (is it Richard?).

As always it is hard to guess over the internet, but here we go.
There is no fuel pump under the bonnet, the whining noise will be from eg the throttle body. The fuel pump is actually at the rear of the car, so if you cannot hear it when it fails to start we have our top suspect - fuel pump not running.

Now, there is a common problem with the power supply to the fuel pump from the rear SAM unit, a loose connection at the plug is all. Might be a cheap fix this one, and after the old W202 you deserve one of those!

Good luck, and keep us posted.

Feel free to give me a call if you wish, or pop by some time for a chat if you are ever in sunny Stowmarket :D!
 
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nebulaman

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C200k (2001)
Had a look at the Fuel Regeneration Valve today and can't really tell much. Had a look down the inlet connector and it is a little grubby so I phoned a garage close to me to see how much it would cost for a new part. They only get their stuff from the main dealer: £87.00. I think before I start spending money on something it may or may not be, I am going to phone my indy when i get some time off and get her booked in (got some wheel alignment issues too). I was going to hold off until my B service in 6000 miles but I don't like getting back off a long job at 3am only for me to spend ages trying to start the thing!

Personally I think it is a fuel pump problem as it starts straight away after a run. Just hope that if the fuel pump needs replacing that it is an external job????
 
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nebulaman

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C200k (2001)
I was just reading about other causes to my problem and one item discussed that other spurious faults can be thrown up. I sometimes get a warning that the licence plate bulb needs checking. Could this be a problem with the rear SAM and/or wiring? I think this maybe what Alex was hinting at!
 
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nebulaman

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Update: Had a bit of a search round today. I checked the wiring around the rear fuse box and swapped the fuel pump relay with the ones of the same type in the front fuse box. Still the same problem.

I tried a different method of starting the car. I turn the ignition on but not to actually crank the engine. If I didnt hear the fuel pump I switched off and tried again. I did this for about 10 mins with no joy. I then tried the same thing but this time i would take the key out and lock/unlock the central locking. Sometimes the pump would start then stop so if i started the engine it would die after a few seconds. If the pump stayed on a bit longer it would stay running. I left the engine idling for a few minutes and then shut it down. I then turned the ignition on to listen for the fuel pump, no joy but the car started.

Can someone explain how the fuel pump operates. Does it operate constantly or is its primary function to prime the fuel lines? I ask this as once the car is running it is fine and has never stopped. Also, the car starts fine once warm. Obviously once the car has stood a little while the fuel lines need priming again.

So as Alex says; I think the fuel pump/connections are the prime suspect. I think i'll give him a ring tomorrow!
 
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nebulaman

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Suffolk
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C200k (2001)
Right! Just to tidy this thread up: Fuel pump is packing up. Cheers to Alex Crow for his fault finding skills!
 

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