psbenz12

Completely randomly the car decides it doesn't want to start and I'm not sure why...

Here's more background:

Most likely not the battery because all the electronics still work and the voltage looks normal.

I don't think it could be the starter because there's no ticking like it's attempting to start.

I doubt it has anything to do with the issue but whenever it happens if I just wait a minute or two and try again, it will start just fine.

There's no service lights and no messages in the cluster.

It sort of seems like it might be something like it not picking up the RFID on the key... any thoughts?

Plutoe

keyless go is a complicated electronic circuit--see someone with diagnostics that can read and pin point the fault in the system.

psbenz12

Sorry, maybe I wasn't clear enough-

I do not have Keyless Go- I am having this issue with the regular MB Key.

I'm not sure what MB calls it, but referring to RFID I was talking about what I know as a "Passive Anti-Theft System" - an RFID in the key that's encoded to your specific ignition to prevent it from starting with anyone's key.

Even cars with a regular metal key and tumbler use it so you can't just go out and make a copy of the key or pick the lock to start it.

Colin G

Can you hear the steering lock disengage when you put your key in?

NZ-Merc

What is the normal voltage value you are seeing when the car does not start, better than 12.5V?

psbenz12

I'll have until it refuses to start again to get the exact voltage I forgot what it was. (It was def 12.??)

Right now I just checked voltage:

- with keys in on position (not running) it was 12.3v
- car started fine and now running it is 13.5v

(got the voltage from the head unit engineering menu)

psbenz12

The steering wheel lowered into position when the electronics turned on, but I didn't check if the steering was locked.

I'll try to make note of that next time it happens.

charles.soori

Might be esl problem. so next time it happens try to see if you hear steering wheel unlock when you insert key.

psbenz12

You won't believe what just happened. Turn the key no start. Kept the key at 2. Turn the headlights from auto to off and the car starts- didn't even turn the key again it just started by the headlights being turned off.

Im confused as hell right now. Next time it doesn't start I'm going to record it.

NZ-Merc

The reason I asked earlier about battery voltage is I suspect that it is getting low enough for these problems to start showing up.

Turning the light off must be just taking enough load of the battery to allow the start system to fire up.

I would with out fail replace the battery as my first diagnostic that I could do my self then what ever happens from there fixed or not.

C300CA

It happened to me twice in six years. I vaguely remember that it didn't start in P, shifted it to N but still didn't start. Back in P, pulled the key out then back in. It started normally.

IGB

+1.....

At 12.3 volts (voltage while engine is off is the critical number), your battery is only slightly below the minimum standard form it to get enough juice to start. And this is why it's an intermittent problem.

If your battery is anywhere near 3 or more years old, and once it starts to lose charge, it won't be long before it completely dies!

psbenz12

Just wanted to update this thread for anyone searching-

For me it ended up being a bad relay in position N in the fusebox under the hood.

I also replaced the battery just to be safe.

The relay is $17.99 at the dealer- I picked up a backup to keep with me as well so I wouldn't get stranded anywhere.

Part Number 002-542-72-19

Dzuliano1991

Hi guy i got a Mercedes Benz SL500 R129 from 1993 L reg and i can't start the car i was driving it home and sudently an some kind of oil start pouring from top where the rear mirror is where those too little lights are it was pouring down to on the main console and the gearbox selector so i stopped and switch off the car and start wiping the oils from everywhere after like 20 minutes of wiping the oils off from the seats and the centre console i was ready to start the car so i out the key in and i twist it once then second time all the light come on as it should ( the headlights was switch off ) then i try to start the car and it does start there is no cranking sound noting its silent i can move the gears from P to D N R any but it still won't start the steering wheel is heavy i am not sure what's wrong i have 2 keys and i I tried both and no luck looks like battery is fine as everything works radio headlights windows but it won't start at all

Please guys help me out