I have 2000 s500 and sometimes it will start sometimes it will not ... i have read other posts which point to crank position sensor??
but the car does fire it just doesnt come on.. and there is no common trend i have noticed.. it happens in all temperatures . .. it happens while im driving the car just shuts off!.. it happens first thing in the morning after sitting all night.. and it happens right after the car has been comming on .. sometimes if iwait 5-10mins.. it will turn back on .. but sometimes it needs about an hour or 2 and it will start back up..any ideas what this could be? its extremly dangerous and i need to fix it because its mostly happening while im driving and the car is in motion.
any help plz!

 

sounds more like L5 sensor before replacin any components have it diagnosed by MB or any body who has a good scanner..................

 

whats the L5 sensor?? can you please give more information on that? I replaced my Crank Position Sensor and my car still sometimes doesn't start!

 

.. i think the L5 is the same as crank position sensor isnt it??
vovpar- you changed the cps and it still does it?? thats what i dont want to happen to me..
could it be fuel pump?

 

L5 is a crank shaft position sensor,ok you ve renwed it, check the fuel pump relay thats a common fault on this model the relay does play up............relay is based on the rear passenger foot wel above there is a small cover if you pop it out you ll be able to see the relays its relay letter T you need to check or swap relay with the next on the same line and if its ok after swapin,let me no how you get on ..

 

i dont know what you mean realy letter T.. .. i have removed the cover rear passenger footwell.. (where there is a light that illuminates floor at night) i see fuses and accross the bottom i see 6 relays?is this what you are refering to?

 

yes excatly that is wat i am sayin you need to find lettrs like T SOLT IS FOR THE FUEL PUMP RELAY..........

 

Hi mobenz.

Your fault could be caused by many things however the CPS Crank Position Sensor was the most likely cause.

I suggest you start at the beginning.

Have any codes been stored in the OBD On Board Diagnostics?
Note: CPS doesn't usually result in a code being stored.
Sure your CPS was a genuine MB spare and new (i.e. working?)
Whats the service history on this car. When were the plugs last changed etc etc?

CPS is usually associated with either hot running CUTOUT requiring an extended cool down period before working again or alternatively no start whatsopever.

Fuel pump is the next likely fault. The relay can give problems but so can other components in the system. e.g. oil pressure switch, ignition switch.

If changing the relay doesn't work (only takes a moment or two) I suggest you wire an indicator lamp across the fuel pump terminals and observe this light when the car will not start. i.e. Is power being supplied to the pump when the engine will not start. This will quickly point the finger towards the fuel pump system or alternatively suggest you should look elsewhere.

 

It was crankshaft position sensor being defective 2 times!!
thanks to everybody who replied! car works now