Help C240 wont crank

[dangermose240]

Help I have a C240 that wont crank, When I insert the key the dask lights up and all looks ok but when I turn the key nothing.

I have a Star system and have tested the keys and then the EIS and the keys are fine and I get the start signal from the EIS
so its not that.

I jumped the purple wire in the front SAM to the +terminal and the starter kicks in and cranks so I dont think its a starter problem.

I also swapped out the starter relay for the Horn realy and this didnt do anything.

I checked all the fuses and nothing is blow.

I scanned the gearbox and the gear selection seems correct and shows no errors.

Battry is old but showing 12.4v on Star.

I cant test any of the relays as you need a socket box add on for the star that I havent got.

Could this be a dodgy ME-SFI, Is this the main computer? If I get a second hand one can I plug and play or does this also hold the key
information.


Please excuse my lack of knoledge if I think I have all the names correct, Am a bit lost on what to try next.

Many Thanks


Chris

 

[television]

Is the car a 202 or 203

 

[dangermose240]

Sorry total lack of car information its a 2002 W203.

 

[robparker]

Just to chime in quickly, my friend had this exact fault on this same model the last week and diagnosed it as the ignition switch, as it could be hot-wired and started like yours, one fitted from MB and made no difference, it turned out that the starter solenoid was actually the fault all along, and a replacement starter cured it.

 

[dangermose240]

Do you know if there is anyway to test the starter solenoid? Just to confirm if you friend jumped the purple wire on the front SAM onto the battery it would crank?

Also couple other things to add, When I took the lid of the front SAM there was condensation on the lid! The car had this problem intermittently over a few week and would go after a few attempts but now nothing.

 

[Steve@Avantgarde]

KK relay is the likely fault here. Go to front SAM box and you will find relay K. Replace that and it will probably start.

Common issue.

 

[dangermose240]

I switched out the relay for the horn as they are the same and it still no luck.

Is there anyway to check that the relay is working.

I think the purple wire from the front SAM is the feed to the starter motor, If I put a multi meter from this to earth when I turn the key I should get out put (the trigger to the starter) and I don't, I'm guessing.

Is it possible to pull the solenoid and put a meter across the trigger to see if its getting a signal? or jump the circuit to trigger the starter?

 

[robparker]

Do you know if there is anyway to test the starter solenoid? Just to confirm if you friend jumped the purple wire on the front SAM onto the battery it would crank?

Also couple other things to add, When I took the lid of the front SAM there was condensation on the lid! The car had this problem intermittently over a few week and would go after a few attempts but now nothing.

Crank and indeed start, drove it to Exeter to buy the ignition switch.
Steve is the expert and I would look at his suggestion first off.

 

[Steve@Avantgarde]

Do you have a test light? Simply pin it into the purple wiring plug on crank, if it lights up you have full drive authorisation an it should crank over. If it doesnt then the starter will have failed.

 

[Alex Crow]

If you have STAR, carry out the tests for drive authorisation in the EIS/EZS, and then check actual values 'star engine' in the engine management system.