SLK320 not starting - where do I start?

[mikevernon]

Help! My SLK 320 won't start.

It is a 2002 car with 24k miles and has always run perfectly, but I haven't used it for 6 months. I replaced the battery and it started first time as usual and ran normally, but a few days later it refused to start. The starter motor cranks the engine healthily enough but it just doesn't fire.

Now here's the odd thing. A couple of times it has fired and run normally, but only for 2 or 3 seconds after which it cuts out then won't fire again. At the moment there's no sign of firing, even if the engine spins on the starter for 10 seconds or more.

I really don't know where to start looking. The problem sounds electrical because it either runs or doesn't run, but I suppose it could also be related to the fuel delivery. Unfortunately I'm feeling daunted by the complexity of the engine and all the unfamiliar components, so I haven't yet checked for a spark at the plugs or fuel at the injection pump. To tell the truth I haven't even located the plugs yet, or a suitable place to check for fuel!

Any ideas?

 

[BlackC55]

First thing is to check for fuel and spark.

basics first.

 

[television]

Its worth measuring the crankshaft sensor to check that it is not open circuit

It should be 1k ohms when good

 

[Benzowner]

Its worth measuring the crankshaft sensor to check that it is not open circuit

It should be 1k ohms when good

That was exactly what I just had to replace on my S320 petrol, very similar symptoms to what you describe.

 

[BlackC55]

Its is most likely to be the crakshft sensor though.

 

[Bazzle]

Could also be a dry joint on the K40 relay board.

http://www.benzworld.org/forums/r170-slk-class/1263021-k40-relay-circuit-associated.html

Bazzle

 

[mikevernon]

Thanks for the replies so far.
I've now noticed that the tachometer needle doesn't move while I'm cranking the engine, which seems to suggest that the crank sensor (CPS) isn't working. So the next step seems to be to remove and test it.
I think I've located it correctly, just below the rear of the left hand cylinder head (ie passenger side on my RHD car)? Not the easiest component to access, but not impossible. The wiring and connector plug have a black plastic cover. Can anybody tell me how to remove the plug without breaking it? Is there a clip which I need to release?
Also, where is the best place to buy a new CPS?

 

[Howard]

Hi Mike,

If you do a search for ' crank position sensor ' you will get a bunch of threads on it ...

Reading through a couple it appears that the CPS is approximately £45 from a Bosch centre or £85 from MB ...

Good luck , hope you get it sorted ..

H

 

[television]

Its 5 in the link, Best from Bosch at £48 or MB at £78


best to measure it first.

Bazzles post is interesting as well
http://www.detali.ru/cat/oem_mb2.as...660716.667&CT=M&cat=19Y&SID=15&SGR=075&SGN=04

 

[television]

Thank you Bazzle for that super link, and I have stored it

 

[mikevernon]

I'm still struggling to remove the wiring before I can take out the CPS.
Can anybody tell me what kind of connector is used?

EuroCarParts and GSF both charge £35-£36 + VAT for a new CPS.

 

[television]

Just press the release clip and the top pulls off.

Do be careful with the other make, they may not last long

 

[mikevernon]

Television. Sorry to be a pain but I still cant remove the connector. I can't see the clip you are referring to.
Here's a link to a couple of photos Ive taken.

http://picasaweb.google.com/mikevernon9/Cps/photo#5151654273237450226

I think you will need to copy the link and paste it into your browser.

 

[television]

If the top will rotate then you have the same as in the first picture and you just press the two ends on the long side and lift off, it may be tight as it has a seal.

the one in the bottom picture, you just press one side to release the top

 

[pac280]

Crankshaft position sensor bolt

Can anyone tell me what sort of bolt holds the sensor in place once the connector has been removed ? I got a mirror to look at it since its hardly visible on my E430 engine but it doesn't look like a std metric bolt. I checked some other forums (USA) and they describe it as requiring an E8 socket/ what on earth is that.

If the top will rotate then you have the same as in the first picture and you just press the two ends on the long side and lift off, it may be tight as it has a seal.

the one in the bottom picture, you just press one side to release the top

 

[robert.saunders]

Isn't E8 reference TORX?

 

[mikevernon]

Help! I'm still struggling with this crank sensor. I've removed the torx screw but I still can't extract the sensor. I've tried every type of pliers/molegrips in the toolbox but I just can't pull it out. There isn't much room around it in the SLK which doesn't help, but surely it should come out more easily than this? I'm on the point of trying to break it up with a sharpened screwdriver and a hammer. Any more suggestions?

 

[BlackC55]

Use some penertrating oil and wiggle it side to side and try and twist it.

 

[mikevernon]

I've been trying that but I still can't shift it.

 

[stevesey]

Someone was having similar problems a month or so back, but they got it out in the end. I was told by an MB tech that sometimes the only way is to knock them out from the inside and you don't want to go there, so persist with the oil and wiggling (careful search of toolbox for things that will help you wiggle/lever etc).