W210 Unusual (delayed) cranking problem

[Jonssen]

Hello,
I wonder if I could ask if people would be kind enough to help me with this problem. I have a '96 W210 E280 which developed an odd cranking delay that has been present for a while now - a year or more in fact, but the car only gets used occasionally over the summer.

I first noticed a very small delay (<500ms) between turning the key to the crank position and the starter activating. Odd, I thought, but then the next few times it was normal. Then it occurred again and the time delay became a little longer (say 1 second) - after that it was normal for a while. Over time this situation continued and escalated such that, say one or two times out of ten or twenty starting attempts I get this delay - and the delay has tended to become longer - 20-30 seconds even (and in one case a couple of minutes).

Now it apparently makes no difference if I operate the ignition/starter switch on/off/on or waggle the key etc. All I have to do is switch it to the crank position and wait. There's no obvious sound, no unusual indications, but after a delay (if it's one of those occasions when a delay occurs) it will suddenly crank and fire up as normal. I've tried all forms of inducement I can think of which I can do from the driver's seat but nothing helps - all I need to do is just sit there with the key held in crank position and wait.

I've asked several people about this and no one has been able to suggest anything definite - and any comments I've had all differ or don't seem to make sense.

I can find nothing immediately obvious to cause this and haven't had time to remove the starter or anything like that, but wiring looks fine as far as I can see. The only thing that I have found that might have had any effect is when I've tried multiple successive starter activations - not actually starting the engine but just enough to fire the starter into engagement and commence cranking - if I do this about 10 times it seems to extend the time (i.e. the number of normal cranking occasions) until the next recurrence of the delay.

Unfortunately I don't have a wiring diagram to enable me to see what is in the circuit or where I can access connections to test the system. And as it's intermittent, the fault won't occur when I'd like to help with diagnostics! The other thing is that there's an after-market immobiliser fitted of which I've no details - I don't know if that is in the crank circuit or not, but experience seems to suggest this is not the problem as I can't associate it with the difficulty.

So, has anyone any clues? Or any wiring diagrams?

I don't really want to take this into a dealership as I think I'd end up with a very big bill and I don't think the value of the car justifies it. I have a feeling it's something simple... I could be wrong!

Any assistance greatly appreciated.
Thanks, Bob

 

[television]

Hi Bob and welcome, you must first establish if the alarm isolates the starter, if it does and uses whats known as a K38 relay, this is known to have poor connections, if you have one it will by under the dash behind the console on the firewall

 

[beemerjay]

Either that or the solenoid is all gooed up with infrequent use and getting worse?

 

[BlackC55]

I would be probably be looking at the ignition switch as the problem.

 

[C220GJS]

Check your starter cable where it passes through the floor at the passenger footwell. I had a problem similar to yours and eventually found that the starter cable had burnt out at the bolted connector there,the break was not obvious as the cable is clamped in position and was making intermittent contact after a time delay like you describe.
Mine is a W202 but I think the starter feed is similar on your w210.

 

[Jonssen]

Hi guys and thanks for your responses.

Malcolm (Television) - when you say alarm, do you mean the aftermarket immobiliser or the cars normal MB alarm system (early type fold-out key with single IR button)? What does a K38 relay look like please? Is there a normally a relay (or any other connector) in the circuit between the ignition switch and the starter solenoid as standard?

Beemerjay - I wouldn't rule that out but frequent/infrequent use doesn't seem to make any difference. Sat in the garage for weeks, months, or over winter it stands just as much chance of working first time (or not) as it does if I'm using it regularly several times a day over the course of a week or so. If I knew where the starter solenoid wire ran, I could try to access it to test if it's getting a feed - it's just so impractical to do that at the starter itself having to jack the car up and crawl under and whenever it's been on a ramp the problem didn't show! Anyone with a wiring diagram?

BlackC55 - I'm told it's just a simple (ignition) switch on this (early W210) model, in which case I'd expect that operating (on/off/on) it would tend to clear the fault, which it doesn't. I used to do that when the fault first started to show up but found it didn't achieve anything (nor does resetting [activating/deactivating] the third part immobiliser numerous times). So, I just turn it to crank, hold it there and wait. Most times it cranks normally, occasionally there's a delay and then suddenly it will crank, start and run.

George (C220GJS) - Yes, I know the one you mean and it all looks ok. But if it were a open circuit at this point, would I be correct in assuming that the starter solenoid would still receive it's supply from elsewhere and hence I should at least hear the solenoid click?

Thanks, Bob

 

[C220GJS]

Bob, you are correct in that the solenoid would be energised making the connection to the starter from the battery, but in my case there would be a delay until the current overcame the resistance at the faulty cable(anything from 2-10 secs). Eventually it failed completely and I replaced the starter to no avail, then on unbolting the battery cable clamp at the point where it passes through the floor I found the cable had burnt through where it it fits into the connector.
Is it possible that in your case a similar situation is taking place on your solenoid feed , maybe resistance in your ignition switch,solenoid or fusebox ?.

 

[television]

The relay K38 was a starter lock out for use when alarms were fitted.

When this is fitted the starter wire from the ign switch goes to the relay, then on to the starter solenoid, we had 3 cars this year where the connections were poor causing the delay or non start until the connections had arced together on the sane principle as George describes for the starter motor

When fitted they are behind the radio

 

[Thegemmesabogie]

Presumeably there is still some form of inhibitor on the gearchange in these cars to stop one starting it when in gear. Have you tried cranking when in neutral just in case it is duff only in park?

 

[Jonssen]

Hello again everyone,

Thanks for your help so far. This is my first MB, so I have no experience of working on one and I'm just working by intuition and common sense.

First, I need some help removing trim please:-

1) How the under-dash panel fixes where it turns downwards and abuts the centre console so I can remove it fully?

2) How to access behind the centre console to look for the "K38 relay" and also replace a heater control bulb whilst I'm at it?

3) Looks like the small tray section below the radio console and above the ashtray should come out some how?


Now, an update. When I went to try to sort this out today, the fault was fortunately present, so I was able to rule out starter motor, s.m. solenoid and main B+ feed and any test any interlocking on the auto shift lever position. I also checked feeds at the fuse box, which all seemed to function normally. There does not seem to a fuse dedicated to the s.m. solenoid in there.

So I tried to look for the "K38 relay" but 4) I'm not sure what it looks like?

That was frustrated by difficulty to fully remove the trim (see above). I did find the immobiliser. On the sensing module (detects a small "keyring mounted fob" which you wave at the ignition switch before inserting the key) it is marked "HRH VERTRIEBS GMBH", "SAFE 1-11T", "KBA9621". This connects to another "black box" measuring about 4" X 5" x 1.25" which is fixed firmly to the car up under the dash on the right hand side. I guess this is a relay box as it clicks when the immobiliser activates. This seems to have 8 wires coming out of it - all black insulation and light gauge (0.5mm2 at a guess). One goes to earth, one heads to the rear of the car along the driver side sill. The other 6 (it looks like 6) are wrapped into two bundles of three and join the ignition switch loom and the bundle is wrapped in insulation tape. What happens under the tape I don't know, as I can't get clear access to check further at the moment (trim in the way).

Other than that I didn't see any other relay yet… But I can't get good access to see yet… There's a lot of spaghetti under there!

5) If I don't find a "K38 relay" can someone tell me if there are any connections in the "crank" (s.m. solenoid feed) wire between the ignition switch and the starter?

Thanks, Bob

 

[television]

Hi bob is your car a 210026 on the first 6 VIN numbers

 

[Jonssen]

Hi Malcolm,

WDB 210053 2A206802

Bob

 

[television]

Hi Malcolm,

WDB 210053 2A206802

Bob

OK I will do an exact search Sunday night, maybe be first thing in the morning if I can, its bed time now

 

[television]

Pin number 50 on the ign switch goes to pin b2 on the N65 k2 starter lock out relay, pin f goes to the engine connector X22 and on to the starter motor solinoid

X22 is nearside on bulkhead

I have run out of time to find where N65k2 is

 

[Jonssen]

Hello all,

Well, that was an interesting way to spend Sunday I suppose! Manage to get the under-dash trim off (found some pics in another post which helped a bit) so now able to get clear access. Been over every connection I can find, even opened up the relay boxes (assume one must be the N65k2, but it's not marked as that) and cleaned the contacts on the open relays. They were all in good nick. Traced the starter sol. wiring - it's a mauve wire about 2mm2, so quite thick! Checked continuity - all good. Open circuit (no solenoid load on it) and there's 12v available when I turn the ign. sw. to crank. Connect the load (solenoid) and woops, the voltage vanishes..!!

Traced back to the immobiliser - it's there in the crank circuit. Why I do not know, neither the wiring loom nor the relays are big enough. In fact they are probably not big enough for the other circuits either! I'm caused to wonder what sort of people design these things - and it's a German product too!

As for the people that install them, well, I've very little faith in auto-electricians but you would think anyone with the basic knowledge of electrics would realise that if the vehicle manufacturers use thick wires they have done it for a good reason and hacking to the loom and inserting a device with wires about one quarter of the size just doesn't make sense! Ok, so they probably don't take the lid off and see the relays are only about 1cm cube and enclosed (would they know?) but the designer who gives them a drawing and tells them to stuff it in the crank line without an interposing relay surely should! Needless to say there's the usual evidence of several attempts at wiring illustrating the installer didn't really know what he was doing. A good kicking needed all round IMHO.

Rant over for the moment....

So, I now consider the problem is either a) the ignition switch or b) the immobiliser. I'm erring towards the immobiliser for the reasons mentioned above, but I need to prove it conclusively. Unfortunately it's difficult to test the ignition switch as you can't easily get the plug back on with the terminals exposed (terminals on the plug) as the pins are held in situ by the cover and once the cover is off it's difficult to remove the plug once you fit it as it's shrouded. Why do I need access to the pins? - because I have to power up the immobiliser in order to test things as that controls other parts of the circuit too (and with no wiring diagram it's hard work finding where the wires go!).

So I was about to try to bridge out the immobiliser within the crank circuit - but then the fault, which had been holding up nicely all weekend, vanished. Intermittent faults have a habit of teasing like that - it's the gremlins - you can hear them laughing at you!! Following that the battery had tired and so had I - so we are now both on charge until tomorrow.

I was wondering if I shouldn't just remove the immobiliser altogether - but for the wire that runs back along the sill... Could that be a feed for a fuel shut off valve?

Bob.

 

[television]

I can check on the colour of the wires for you the one that comes from the ign switch 50

 

[Jonssen]

Hi Malcolm,
50 - I've got that one thanks, it's mauve. There are two red +ve though - ign. sw. terminals marked 30 do you know where the come from?
Tks, Bob

 

[Jonssen]

Hi all,
Update - I've bridged out one of the imobiliser circuits with a switch and I'm now waiting for the fault to re-occur so I can finally pin it down.

Meantime: 1) There are two wires going to the starter solenoid (yes, two on the one "crank +ve" terminal) - I know one is the feed from the ign. sw. and comes from the relay box. Please can someone tell me what the other one is for and where it goes?

Tks, Bob

 

[Jonssen]

Update on this - the issue was the ignition switch itself - poor crank (start) contact (poor switch design?) which would provide a voltage feed when the starter was open circuit, but collapsed as soon as any current demand flowed. The current caused a localised heating effect which caused the contact carrier to warm and distort (like a bi-metal strip effect) thus opening the contact. The contact would not then permit reclosing until it had cooled. Solution, open switch cover, clean contact and bend the contact carrier! Fixed.

 

[Naraic]

Appreciate the up date...4 years on.