Hi all, my oldish but low mileage (32k) slk has decided she won't start unless I talk to her for 30 half an hour (bit like the wife).
In all seriousness though she simply wont start after being a little difficult over the past week or two.
Symptons are - key seems to "stick" at ignition position ( unless she actually starts). The battery has plenty of power and turns engine over easily though there is not a flicker of sparking into life.
There is a lot of strange "electronic" type sounds coming from the unit at the top right of the engine - I don't know what the unit is but it is at the engine end of the fat black tube that comes up from the MAF. Suspect its some kind of air injection unit?? The noise is there in second key position i.e. when all dash lights are on.
Any thoughts welcome from anybody welcome. Thanks Colin

 

no cel? it runs ok once started? K40 relay, but the relay can shut you down while driving. cam position sensor can cause these issues.

 

Thank you for your reply.

The engine will start for a few seconds if I squirt a little Easy Start into what I now know is the throttle body - the engine simply dies again when the Easy Start is used up.
From this I assume this issue is with the fuel delivery system or associated relays. As the car is well maintained and only has just over 30k on the clock I would be surprised if its an issue with the fuel pump.
Any advice on the order of checking things would be appreciated - can the fuel relay be checked on the K40 in isolation?
Anyway any suggestions welcome. Thanks Colin

 

to start, check for cracks, burns or bad soder points in the k relay with a magnifing glass. it's in your relay box next to the battery. one large red 40 amp fuse and five 15 amp blue fuses. there is a brass colored clip that holds it in place. push away from relay. disconnect ground first. you can pry it apart starting on the opposite side from the fuses with a flat screw driver.

 

Thanks for advice. K40 relay solder joints look OK.
Had a breakdown guy out for an hour.
Plugged car in to very expensive PC but no faults codes shown. He "proved" fuel pump ok as showed fuel coming out at plug at front of fuel rail - just below vacuum tube.
Sprayed easy start in to throttle body and car started for a few seconds - so appears ignition ok.
So, in summary, we have fuel getting to injectors, we have spark and the engine turns over no problem.
He was an old school mechanic, seemed to know what he was doing but has admitted defeat.
So before the car goes off to Mercedes any last minute pointers to check would be very much appreciated, thanks, Colin

 

maybe the camshaft position sensor. recheck wire connections and vacuum lines