C180 Sport starting problems

[Northy]

Hi there, I am new to this forum but would really like some advice on a problem I am having with my car.

I have a 'V' plate C180 Sport - it's done an astronomical 280K miles and has been fine up until this point.

A while ago is started to develop two intermitent problems;

1/ sometimes when you turn the key it makes a metalic clicking sound (from the starter) but does not turn over.

I put a new battery and starter on it, and it was still doing it. So I took it to an auto electricians. They replaced the starter control module and also fitted a by-pass switch which can be used when it does this clicking thing. I haven't needed it until today. The fault appears to be back. So to start it now, I have to get someone to hold the key in the cranking position (which makes the clicking noise) and then press the starter by-pass switch. It will start first time like this.

The electrician advised that when you turn the key, it is a 'request to start' which then performs a number of checks before allowing the starter to turn. Clearly there is a problem somewhere that is stopping it from being allowed to start.

So my question is, does anyone know of anything else that cause this? Or have any recommendations on how to fix it?

The electrician thought maybe the ECU was going to give up soon and that they are mega £££ to replace.

2/ the second problem is also intermitent, but it seems to happen if I pull away with too few revs. The car does not stall, but kind of 'hunts'. The tacho bounces between 1000rpm and 1400rpm and the engine does not respond to applying the throttle. You can put your foot flat on the floor and nothing happens, it just continues to hunt like this. If you turn it off and back on, it's usually OK.

Any ideas?

Apologies for such a long winded first post! But I am clutching at straws with this one!

 

[mattkh]

starting

of checks before allowing the starter to turn. Clearly there is a problem somewhere that is stopping it from being allowed to start.

So my question is, does anyone know of anything else that cause this? Or have any recommendations on how to fix it?
Any ideas?

Hi

What are the first 9 letters of the chassis number ?
Do NOT type in the whole number.

 

[Dan996]

With regard to your first problem it sounds like a earth fault somewhere our old work vehicles do it somtimes but im sure someone will correct me as for the second problem i dont know.

 

[Northy]

The chassis number starts: WDB202018

When the battery was replaced (under warranty by the RAC) he tested the earths and said they were fine, he even ran an earth direct from the battery to the earth strap that connects nearest to the starter.

Cheers for you help guys, I am lost on this now!

 

[television]

Your fault is with the starter lockout relay or the DAS on the alarm. It is not ECU related. In other words when you insert the key, it is recognised,,then the starter feed is energised in key2 this 12v goes to the starter lock out relay that feeds the starter solinoid, this relay is also isolated by the alarm.

Malcolm

 

[Northy]

Malcom, thanks for your help with this.

Please excuse my ignorance, but what does DAS stand for? Do you think it's worth a go changing the starter lockout relay first?

 

[television]

Malcom, thanks for your help with this.

Please excuse my ignorance, but what does DAS stand for? Do you think it's worth a go changing the starter lockout relay first?

DAS is drive authorize system, when you insert the key if recognised it allows you to turn it to the start position, the 12volts energizes a relay that should energize the starter,sometimes this relay often known as a K38 is an adition to the starter lock out in the alarm.

It would be worth having someone who understands these circuits to look at the car, the click that you hear would be the relay, but if the alarm is faulty the starter cannot turn as it is further isolated as the two relays are in serries.

malcolm

 

[Northy]

The clicking is repeated. So you turn the key and it makes a loud metallic 'click, click, click, click ....repeat.... ' Almost like the solenoid engaging, but not cranking the starter. I am assured by both the RAC mechanic and the auto electrician that the earths and wiring are fine. Would these faults show up on the diagnostic tester? As the guy who looked at it before said it came back all clear, despite not starting!

The key turns ok when I put it into the ignition.

Cheers for the help Malcolm

 

[television]

The clicking is repeated. So you turn the key and it makes a loud metallic 'click, click, click, click ....repeat.... ' Almost like the solenoid engaging, but not cranking the starter. I am assured by both the RAC mechanic and the auto electrician that the earths and wiring are fine. Would these faults show up on the diagnostic tester? As the guy who looked at it before said it came back all clear, despite not starting!

The key turns ok when I put it into the ignition.

Cheers for the help Malcolm

No this would not show up on a diagnostic. It is only a matter or finding the wire from the ign switch follow to relay or/ and alarm, the fault is simple,though a little hard to find, but it should be under the dash on bulkhead. If the fault is in the alarm this could be by passed.
if you are saying that it clicks al the time, there could be something on the relay stopping it from closing.
malcolm

 

[Northy]

I think tomorrow i'll go and have a nose around in there and see what I can find. I am sure i'll be back on here with feedback!

Any idea where I can get a more detailed wiring diagram from - the one in the haynes manual is really basic.

 

[television]

I think tomorrow i'll go and have a nose around in there and see what I can find. I am sure i'll be back on here with feedback!

Any idea where I can get a more detailed wiring diagram from - the one in the haynes manual is really basic.

I see that you have posted your vin, cant guarantee anything but I will take a look.

malcolm

 

[Northy]

Hi Malcolm,

I spoke to MB and asked about this starter lockout relay - as I wasn't sure where it is or which one it is. They advised it won't have one as it's a manual. Sorry, perhaps I should have said that before..

Any other ideas?

 

[television]

Hi Malcolm,

I spoke to MB and asked about this starter lockout relay - as I wasn't sure where it is or which one it is. They advised it won't have one as it's a manual. Sorry, perhaps I should have said that before..

Any other ideas?

It is still isolated via the alarm, see what I can find out later in the day.

Malcolm

 

[Northy]

Any joy with this Malcolm?

 

[Northy]

bump bump bump

 

[Northy]

It looks like I'll have to replace the ECU - anyone recommend a company who can supply a new one?

 

[C220GJS]

Try here;www.bba-reman.com.They will rebuild your own unit, saves any problems with recoding ,etc.

 

[Northy]

I got a replacement ECU and key recognition module from Dronsfield Mercedes for £250 + VAT and it's appears to have sorted all the problems. It started first turn of the key and seemed to run better than ever!

Hopefully that's the end of it now. Cheers for you help guys.