Help Need SLK R170, Detailed post, sorry

[PAUL R]

Hi People, I really need some help please,
I have an early SLK R170, and have a starting issue, basically it won't start or even crank over.
History:
Drove the car out of our garage at home and parked on the drive for a couple of days, all was fine, (no issues before with anything) Come to put the car back into the garage it ran for a couple of yards, maybe feet, then cut out. Won't even turn over.
Me and the good lady pushed it back into it's now resting position.
Called the AA who got the car started after an hour fiddling and messing around the box that contains the K40 relay module, the box just by the battery.
He Said that if it fails again to call us as that's what we are paid for, also gave the offer of recovery to which ever nominated garage I chose.
As I do my own oil changes, I am out of touch with main dealer practices, and to my expense over the years I have stayed away from the due to cost and less than honest information. I have never used an independent garage.

I need either a good recommended auto electrician who is up to speed with Mercedes SLK R170 cars
Or personal input from experience gained, with this problem. so that I can rectify the problem myself with your help of course.

The Facts :
Key position 1 acc come on (radio) no problems
Key position 2 all dash lights show and after 3 or 4 seconds SRS light go's out normal.
Key position 3 No start sequence initiated, no relay's trip in, no fuel pump buzzing, But main cooling fan runs at high velocity, (as this is default mode for a problem)
I am quite capable of rectifying most faults on my cars and have access to most tools, but I am quite all at sea with this one.

I have checked that there is power to the K40 relay box, which is what an internet search says is the most common fault, that causes this problem,
As the horn and air pump from the central locking is working. So there must be power to the relay circuits,
I can not check the other 3 relays as there in the box, the other 3 relays control stability control, fuel pump, and engine management.
I have had the K40 relay box out of the main box and checked for tracking on the circuits and nothing no furring of or burning of the soldered joints and all the relays move without any problems.
As this is an early car the immobiliser / alarm was dealer fit, I have dropped this out of the system and it has had no effect, and the alarm works fine.

So if there is any helpful soul in MBCLUB world who can point me in the right direction I would be most truly grateful.

Paul R

 

[maxjak1]

Hi, same fault, I charged the battery overnight and now runs fine, bit strange the fans come on flat out it just flattens the battery more!
No one offered any advice for me either, I suspected the K40 as well, I have a unit that the fuel pump relay doesn't work, just by pass it to make the fuel pump work( had mine on a switch until got another module). This made no difference, will take it home tonite and check earth straps tomorrow, could be the gearbox switch on the gearbox lever not working maybe.
If I find anything will let you know

Cheers

 

[AMGeed]

I wonder if both instances point to a faulty EIS?

 

[Tigger]

Check the relay for engine management which you can try replacing.

I have a similar issue on a w211 which I have traced to a dodgy earth connection to the engine management relay.

RAC guy helped me cludge it for the moment by using a jumper wire to the body.

The earth seems to be a switched earth so I have to connect when I want to use the car and disconnect when I'm done. If I leave it permanently connected then radiator fan comes on at full speed on ignition off.

I think I need to take the fusebox apart and check for bad connection/corrosion.

 

[maxjak1]

Hi, went back to car drive home 40 miles, the fans are flat out, nothing from when I turn the key, all lights on, lifted bonnet module box, hit the cover fans stops car starts, runs perfect, will check the K40 relays in the morning, will buy a new k40 module genuine, should cure it will keep you posted

 

[PAUL R]

Mine turned out to be the K40 relay module, £154 from the dealers all is well now

 

[maxjak1]

all sorted

Hi Paul,

It definitely a relay which is faulty or the soldering, remove fuse F3, same symptoms fans flat out, put fuse back all good, the contacts look a little dirty.
The relay is the same one which powers the fuel pump, second relay from the end.
have ordered the module, need a bit of reliability with the electrics.
:bannana::bannana::bannana:

 

[PAUL R]

Hi Paul,

It definitely a relay which is faulty or the soldering, remove fuse F3, same symptoms fans flat out, put fuse back all good, the contacts look a little dirty.
The relay is the same one which powers the fuel pump, second relay from the end.
have ordered the module, need a bit of reliability with the electrics.
:bannana::bannana::bannana:

I did exactly the same thing, reflowed the all the soldered joints, and checked for continuity(which was there), re fitted the relay unit without the protective covering and bridged open the centre relay and the car fired up, removed the cocktail stick from the centre relay and the engine died, changed the 680ohm resistor and it still would not close the contacts on the centre relay, so I came the conclusion the track under the relay had failed :fail, so after hours of work I bit the bullet and purchased a new unit, oh by the way did you find the horn relay, when you do it makes you jump
Good luck
Paul