CLK350 M272 cranks but won’t start

Kompressor_Dude

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Hi all, it’s been years since I was on the forum, however I’ve got an issue I just can’t solve and hoped I might find the answer here.

I’ve owned my ‘05 CLK350 for about eight years and it’s been very reliable… although its only covered 34k in that time. On a few journeys some months back power disappeared and the dash lit up, but then all came straight back to normal. Last weekend about a mile from home on cruise control at 30mph it spluttered and died over the course of about 400m. It didn’t sound mechanical, and now turns over strongly but doesn’t start.

RAC man couldn’t find any codes and towed me home. I can’t find a code or any damages fuses/leaks etc.

I changed the crank position sensor as read they can fail without a code and the symptoms seemed to match, but it’s done nothing. Before I buy any more parts I think I need to check the relays, fuel pump and filter (both original) and possibly compression test it?

I can’t hear the fuel pump priming but it is getting power so it’s fuel or ignition based I expect?

Does anyone have any experience or thoughts? I’ll likely speak to Ollie and trailer it over there if I can’t fix it, but I like to do what I can myself so any direction would be very much welcomed!

Thanks,
 

Jigglyjohnson

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Hi,
When you crank the vehicle does the rev counter move ?? If it does then the crank sensor is working. If not then you.need to check the wiring from/ to the sensor and possible has the sensor that has been changed the correct one?. Ideally you.need a star machine connected and check the drive authoration for the vehicle to see if the vehicle is all good. I would then check all the feeds and earth's to the engine control unit to 100% make sure everything is okay
 
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Kompressor_Dude

Kompressor_Dude

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Thanks for your reply. Tach doesn’t seem to be bouncing, however it starts right up with a bit of fuel poured into it. Would the ECU not withhold spark too if it were being preventing from running due to a sensor/computer issue?

I’ll have a good check over of the earth points when it’s light tomorrow.
 

E55BOF

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If it fires up with fuel poured in, there is a spark. If the CPS were faulty, there would be no spark. It sounds like either a mechanical failure of the fuel pump, or electrical interruption of the power feed to it.
 

E55BOF

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A Star will pick up codes that more d-i-y code readers can't. Good luck.
 

Flyinspanner

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Do you have fuel pressure in the engine bay when cranking?

if fuel pump can’t be heard it could be fuel pump / or relay / fuse?

check for power at pump.

has fuel filter ever been changed? Could be blocked?

take fuel cap off, if big whoosh of air into tank, try starting, cap off.(could be venting issue, vacuum in tank overpowers pump.
 
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Kompressor_Dude

Kompressor_Dude

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Thanks everyone - it wasn’t STAR but the recovery guy had a top-end scanner and couldn’t see errors on anything. No lights on the dash either.

No pressure at the fuel rail but there is 12V at the fuel pump connection so I think this means fuse/relay are ok.

Can I assume my issue is between the fuel pump and cylinders? It’s never had a fuel filter (nobody seems to know where they are in these models?!) but seems plausible that this would be dirty and cause loading then failure of the fuel pump.

I have two hatches under the rear seat. Near-side with the electrical connector is fuel pump which I will pull and bench-test. Is the filter in the actual pump, in the off-side hatch, or underneath the car?

Is there anything else between these components that could cause issue? It’s never even coughed since it failed so I think pump sounds more likely than anything intermittent or bank/cylinder based downstream?
 
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Kompressor_Dude

Kompressor_Dude

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VIN begins WDB209 356 2F if that helps locate the fuel filter?
 

Flyinspanner

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It appears some have an external filter and some may have a filter combined with the pump (but that may just be USA models?)


I suppose you may need your full vin at a dealers to identify? Or a visit to your local indie?

it may need a pump - if no filter attached, then next service it could be prudent to ask them to change it. I think it’s recommended at 60k
 
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Kompressor_Dude

Kompressor_Dude

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The car’s done 145k and there’s no paperwork for anything in the fuel system ever having been replaced. I’ll put a new pump in and if the filter isn’t integrated I’ll find and change that too.

I have a part number of A209 470 0294. Fingers crossed that solves it.
 

mioba

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Change the fuel filter first a much cheaper option that doing both the pump and filter.

at least then you will know its been done.

They are every 4 years due I would say.
 

E55BOF

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A209 470 0294 is a fuel level sensor, I think.
 
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Kompressor_Dude

Kompressor_Dude

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Merc parts desk quoted me that one - I’ll pull whatever’s in the tank and check. Never known so much confusion over what pump and filter are installed on a car before - they didn’t even know, but guessed it was integrated because there was no separate filter listed.

A filter-only change doesn’t seem worthwhile as the pump isn’t operating, so even if it wasn’t the cause it’s almost certainly collateral damage!
 

IanW

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My 2005 CLK definitely has the filter built in to the pump assembly. I tried (and failed) to replace it as part of routine maintenance.
The pump retaining collar needs some sort of special tool to undo, but IIRC some people have put together Heath Robinson arrangements that work for a while. A Google search throws up an interesting selection of tools. If you do buy or make one, I'd be interested to hear how you get on - my fuel pump is living on borrowed time.
Ian.
 

Jigglyjohnson

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The filter is part.of the pump in the tank on these. The filter I think has a filter bag attached and over time these block up and cause the pump to work harder and hence burn out. Take the pump out and check for debris in the bottom of the tank and then power the pump out the car and see if it pumps any fuel out if you put in a bucket of fuel
 
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Kompressor_Dude

Kompressor_Dude

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I had assumed you could just gently knock those collars around with a screwdriver and hammer? If I can I’ll get the pump out today and post how I did it and what it looks like
 
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Kompressor_Dude

Kompressor_Dude

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So, with a short pry-bar and hammer I was comfortably able to remove the retaining hoops. Battery terminal disconnected!

Don’t remove the near-side one and unpack everything just to realise it’s the fuel sender and the fuel pump is on the off-side. That would be stupid……

Have left it to sit overnight to get rid of the fuel and vapours and will bench-test it tomorrow. I cut a temporary circular fuel-resistant gasket to seal the hole and put everything back together so the car doesn’t become a vapour-bomb whilst it’s removed.

Hope the pump doesn’t work! Oddly enough. Part number matches that provided above which is good. Not gotten into it far enough to see if there’s a filter in there. Pictures inside tomorrow.
 

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