Glyn M Ruck

This is the start enable process:

https://mbworld.org/forums/c-class-w...t-process.html

Have you checked the starter relay in cavity S of the front SAM that I mentioned originally?

You are going to have to methodically go through every item & connection in the starter circuit & also check body earth straps.

You need to check every connection on the front SAM

W203AL

I checked the starter relay and nothing seems wrong but since its a cheap item (around 10 Dollars where i live) i will go ahead and change it tomorrow and see how the car responds to that... When you say i need to check the connections in the front SAM do you mean check the cold joints?

Glyn M Ruck

Remove the SAM from the car by unplugging all connectors. Check & clean all of them with switch cleaner & then plug them in again. Minor corrosion on a pin can cause a CANBus fault.

Also look for any bad joints.

W203AL

Will definitely do this and update the thread... Thanks a lot for the time and help ...

Critter

Not sure of diesel terminology but if the glow plug circuit is not activated then would the vehicle still get the crank signal. Could this be a glow plug relay that is loose or defective. When the booster battery is used the quick flash of voltage may be enough to energize the glow circuit or complete the start circuit.
Also as stated loose ground connection, fastened but not tight enough, similar to a loose battery terminal it is on but you can twist it, so low current functions will work like the lights but the starter draws too much current and the connection can not pass the current.
Also if the glow plugs are not energized then will the vehicle still start (crank) when hot, normally?
Are these not interconnected?
Possible neutral lockout switch effecting cranking of motor.
Hope any of this is helpful.

Glyn M Ruck

The glow plug circuit should not prevent crank.

I thought of the interlock switch but why does it jump start?

niceguyftx

I'm not sure if you have a 6speed manual or not...but this happened to me before and for the sake of my I couldn't find out why my car wouldn't start after changing fuses, starter, and so forth. I later find out the culprit. It was as simple as the switch behind the clutch went bad and even though it was depressing, the switch was bad so was not sending a siglnal to allow me to turn the ignition. Hope it solves your problems, if not, good luck!

Carsy

Good thinking .The auto trans has an interlock switch as well which has to be made before starting.

Critter

Niceguyftx, your fix would be hard to find as it is a simple switch, thats kind of where I was going with the neutral lockout, had a car a while back that would stall every now and then when you went to start it there was nothing, if you opened the door and then slammed it the car would start, turned out to be loose connection on that Neutral lockout.
Just to take this out of the issue have you tried to start the vehicle in neutral. could just be an adjustment issue with the shifter as I see it has 172000km.
Glyn, the only reason I could think of is that when boosted the positive cable is connected to the battery and the ground is usually to the frame or engine bolt, that brings it back to your ground connector comment. Motor to frame ground should be checked.

W203AL

The car is Automatic but does this issue explain all the faults in the dashboard ?

Glyn M Ruck

The spurious dashboard faults are typical of low voltage ~ bad connection somewhere.

Your car still has a brake light switch that interfaces with the interlock. I would check it. It was deleted at the 2005 face lift & the signal was taken from the ABS.

W203AL

Well i checked Relay R and Relay S today and they both work fine. I was told that they either work or they dont therefore if it was them, it wouldnt be once in a while.

I will go ahead and remove the front SAM, check it for any damaged cold joints and clean it as well. Once that is eliminated as well, if the issue persists i will start to follow the + from the battery... and see where that leads me...

This is beginning to become a pain in the *** and i have this car only from two months... Still havent enjoyed it to its full potential...

W203AL

I was going through the thread again ... so far I have eliminated this issues:

Starter Relay S - Its Ok
Relay R front Sam - Its Ok
Motor Starter - New Solenoid and clean motor starter recently
Battery - Brand New and always showing 12.4 V even when it doesnt crank (so its not drained)
Alternator- Checked and the output is around 14.2 V all the time
Fuse 52/31/57 - All ok

Based on your feedback here i need to check:
1. The battery terminals for corrosion
2. Front Sam connectors and bad/cold joints
3. Body Earth straps ? (Help i dont know what these are and how to check them)

Anything else i can include in the to-do list?

Thanks

W203AL

Extra Info :

The remote lock seems to stop working for no reason and then starts working again. As i know its 4 parts than can be faulty. EIS, Antenna, Rear Sam and the Antenna amplifier. The weird thing is that whenever i jump start the car due to the crank issue, if it has not been loocking it from far, after the jump start, it starts working. As if it gets a boost of energy from somewhere. Is it in anyway connected to the low voltage issue or the front sam ?

The other extra info i have is that when i tried to jumpstart the car with another battery not connected with a running car, it didnt start, when connected with a 2002 opel corsa it again didnt start, When i connect it to a running which is around the same size as the w203, my car starts ... does this tell me that its a low voltage issue for sure? anything popping into your mind after this info ?

Thanks

Critter

Earth straps or ground straps are the same, they are the negative side of the battery connection to the frame of the car. Since these straps must connect the circuit to the engine as the engine is sitting on isolators / or motor mounts the negative side of the bat must use a strap or cable from the frame to the motor to ensure good conductivity . When an issue of poor grounds come up strange things happen as the circuit looks to find a ground. A loose ground may spark when asked to transfer current to make something work like in the case of a high draw item like a starter. A lower current draw like a headlight might be okay with a current transfer and operate normally but say when you try to start a spark will occur and the system/circuit will fail. Also corrosion under a ground point will affect the current flow and might be hot to the touch. Your comments on the different conditions of your issue would lead me to look at all these ground connections and check for clean solid connections.
Start at removing and cleaning the battery posts/terminals with a wire brush or battery terminal brush, clean the female ends also, retighten those battery cables, after tightening use some force(twisting action) on this connection to see if it is actually tight. Check to see if there is a start now! , go from there and methodically check the other connections. Even a new battery should have the terminals cleaned prior to use.

W203AL

Thanks a lot for the detailed information... Will definitely do that in the morning with daylight Every mechanic here wants to remove my front SAM but i wanna get rid of all the other possibilities before i do that :S

Thanks again

Carsy

Just a thought, can you put a multi meter across the terminals of the solenoid & starter when you attempt to start the car .

If no voltage or low voltage you can look upstream.

Check the tightness of electrical connections on the starter.

It would also be a good idea to check if the starter brushes were worn & the condition of the commutator.

But I must say the symptoms are looking more like a spurious earthing problem. Try moving the electrical looms around gently with the ignition on to see whether there is any rubbing on cables or broken wires etc.

I think advice from a competent experienced auto electrician may be helpful.

Glyn M Ruck

Remember to check this distribution block for corrosion or burning. Have seen a few bad ones. Mainly burnt.

Glyn M Ruck

Relays can also be power hungry until they latch properly if the coil is burnt.

Antenna amplifier problems can be bad ground/earth related.

This thing is a pain. If it ends up being an EIS problem this will be the weirdest one I have ever experienced.

Everything points to a loss of power transfer somewhere due to a bad connection.

bibauporto

Probably isn't that, but are you able to get S/W and D/N/R indication on your dashboard?

W203AL

Hi,

Yes i can get all the DNR and the C/S on the dashboard (my car has Comfort and Standard i think) ...

Glyn and Carsy thanks, I guess ill go ahead and eliminate as many possibilities as i can until i hit the right spot

kanadian

I recenlty washed my windows with gas station squeegee could this affect ir transmission from drivers side sensor or w.e and what is ir transmission

Glyn M Ruck

IR transmission = Infra red transmission
RF transmission = Radio frequency transmission.

W203AL

Hi guys,

After all the tests and checks (motor starter, front sam, glow plugs, battery etc.) i was told that i have a faulty ECU... which when the car gets connected to another running car , the faulty element gets a shock and resumes working... is this an option ? whats your opinion ?

id like to hear you out before i remove it and send it for repair... can it even be repaired ?!?

W203AL

I happened to have the Not cranking problem at the dealer and when he tried to connect to STAR the ECU was not responding... which lead him to believe that thats where the issue lies...