W210 2.8 petrol M104.942 sudden stop and starting problem

[Jonssen]

So, W210. Petrol 2.8 6 in-line (M104.942) became difficult to start the other day, normally not a problem starting. Ignition on (normal), crank (normal), engine fires very briefly and abruptly stops. Continued attempts initially achieved a slightly longer engine run (maybe 1/2 sec) and again sudden stop. Further attempts achieved, say, 1 sec engine run and then sudden stop leading to 'battery not charging' fault warning. Continuing same procedure extended the run time slightly with same result until after about 10 tries it eventually ran (normally). Reversed out and drove a few yards when had to stop to wait for another vehicle to move, at which point engine suddenly stopped again with 'battery not charging' fault warning. Again a job to re-start much as before with same repeating fault warning (which comes on after the engine stops, not before). Eventually ran (apparently normally) after a few more goes at which point I decided to just drive 100yds and park it up, but left it running (idling) for about 10 mins when all seemed normal before switching it off. (Have yet to try starting it since.)

Before this I'd noted it on the last few occasions of somewhat infrequent use it wasn't quite as 'clean' starting as normal - not always going on the first turn of the key, instead initially firing briefly but stopping. But once it went 2nd or 3rd crank it was apparently fine. (Battery is good and charged, no other known issues.)

On two previous occasions (one about a year ago, one maybe 3 or more years ago) the engine has also suddenly stopped when the car was stationary waiting for a pump to come free at a petrol station. The 'battery not charging' fault warning displayed. Left a few moments it re-started without problem. It has never stopped irregularly otherwise over the 16 years I've had it, to the best of my recollection. It's has no known unresolved faults, has not had any recent electrical attention other than a plug change last year and normally runs a treat. (It has not had a diagnostics check.)

The engine stop is abrupt and instant. No misfires or stuttering. Just 'on' in the one moment and 'off' in the next. (The 'battery not charging' alarm extinguishes on ignition key 'on-off-on' reset.)

Could the fuel injection suddenly cut fuel to cause such behaviour?

This car has a 3rd party immobiliser fitted. I don't know the branding. It has 3 relays, one cuts the ignition, another the starter and, I presume, the third somehow cuts the fuel (but I have not traced this, the wire goes elsewhere to the other two). Would there be an additional fuel shut-off solenoid fitted somewhere, and if so, where might this be located? Or would could it be somehow used to turn off the fuel another way - e.g. does the vehicle have some other (MB) fuel shut-off valve?

What other features of the vehicle might also cause this issue?

 

[malcolm E53 AMG]

Crank Position Sensor (CPS) is a possibility, relatively cheap part and easy to fit

 

[LostKiwi]

Sounds like an ignition fault to me. Fuel issues usually create a 'soft' stop. Ignition creates a 'hard' or instantaneous stop.
This could be caused by many things - bad ignition module, bad ignition lock, bad immobiliser, bad ECU, broken wire, bad coil etc....

 

[Jonssen]

Sounds like an ignition fault to me. Fuel issues usually create a 'soft' stop. Ignition creates a 'hard' or instantaneous stop.
This could be caused by many things - bad ignition module, bad ignition lock, bad immobiliser, bad ECU, broken wire, bad coil etc....

Yes, coming from the 'carburetor' era, I can understand that. But, unfamiliar as I am with petrol fuel injection, I would assume that might be capable of cutting off instantaniously. Is that so? Not sure how close to the cylinder the injection takes place on this engine. Would there be some residual fuel in the port/cylinder - enough to give a 'soft' stop?

Using simple logic, the appearance of the 'battery charge warning alarm' suggests to me that the ignition is powered and that the ECU is generally telling the engine to run (or thinks it should be running). This thought simply comes about because if the ECU was telling the engine to stop, I'd assume it would isolate things like the charge warning alarm from displaying. That is, it would be programmed not to display alarms that aren't required because the status would obviously exist if the engine is being told not to run.

Does the MB ECU system tell both whatever it uses to provide the 'pulse' to the coils (the 'points' / distributor equivalent) and the fuel injection system at the same time? I understand the timing signal for this comes from the camshaft position sensor. Is that correct?

Does the crank position sensor actually monitor position or does it just sense rotation (rotational speed)? That's to say, is it that it just 'counts' (or senses) flywheel ring-gear teeth?

Finally, is there a cheap / easy way for me to be able to read the diagnostics? (I'd consider taking it to an MB specialist but given the nature of the problem I'm concerned I might just get stuck on the way!)

 

[LostKiwi]

Injection takes place in the inlet manifold and is a continuous injection system so there is always fuel in the port.

The CPS monitors the position in the crankshaft and as far as I'm aware is used for ignition timing. The camshaft sensor is used to monitor variable valve timing.

Your car should be of the era that supports a blink code reader. Very simple and easy to use.

 

[Jonssen]

Thanks Kiwi. It's a '96 car.

A little update. There's either none or erratic (and probably low) fuel pressure at the fuel rail. I can hear what I believe to be the fuel pump running - for about 8 seconds after the key is turned to 'ignition on'. (Oddly, to my mind, I can only hear this coming from under the bonnet rather than under the car as I'd expect!) Sometimes, if the pump's been allowed to run a few times before cranking, there's a little fuel pressure in the rail and the engine will run for 3,4,5,-10 secs until it (fuel) runs out. The stopping is still quite abrupt.

So I guess that may point to the fuel pump or perhaps it's non-return valve, or a filter problem, or both. Or might the accumulator (assuming it has one) be an issue?

Comments welcomed.

 

[Jonssen]

Resolution update:
Fuel pump proved to be working fine when powered from direct B+ve. Eventually found the K40 relay box (although some on-line data for this 210.053 suggested it didn't have one!) with open circuit fuel pump relay coil. Obtained replacement relay from ebay seller and replaced the failed one. Takes a bit of time to get the old one off the board for anyone thinking of going this route! Fitting the new one is a doddle.

(There's also enough room inside the K40 case to wire an alternative relay instead, which would also be easier too if the original coil is open circuit as one could avoid having to remove the original relay!)

Fuel pump cover under car is supposed to be simple to remove, but the (3) metal studs welded to body aren't greased on assembly and hence corrode. Although plastic nuts are used to fasten, rusting caused one stud to sheer off and another nut thread to strip. Slightly larger studs and nuts would be better.

 

[Jonssen]

Well, it seems the problems are not over! I've only done a few local journeys (25 miles or so) since changing the relay, when the car started and ran perfectly, today I was moving it just a few yards, parked and intending to leave the engine running, when it just suddenly stopped. No warnings. Would not re-start. Checking, there's no supply going up to K40 fuel relay coil. I put a temp. supply on the K40 input terminal, the relay activates, fuel pump runs. Try cranking, cranks but nothing more. From the wiring diagram it seems the supply to fuel pump relay comes from Engine Control Module (HFM-SFI), so that suggests to me that either something is telling the 'black arts' box not to run the engine or the box itself has a problem. I think I'll need to find someone to examine the diagnostics.

Still seems very strange that two very similar issues suddenly pop up like this within a couple of months of negligable use given it's been so reliable for the past 16 years! Oh well...

 

[LostKiwi]

Check the crank position sensor
Common symptoms are starts, runs for a while, suddenly stops then will crank but not restart.
Injection pump only runs on initial turn of the key to prime the system then turns off and won't turn on again until there's a signal from the crank sensor.

Often the engine will restart after cooling down then fail again when warm.

 

[Jonssen]

Well, I said no warnings but that's the problem with a bright summer's day... I checked again yesterday when it was a bit overcast and now when I turn the key to pos'n 2 I see the rear view mirror LEDs flashing alternatively! So it seems it just decided to immobilise itself. Good job it wasn't on the move, it seems a bit dangerous if it can suddenly do that.

I'll not comment further just now as I'll just go off on a rant...

 

[Jonssen]

Things get worse...
There was a suggestion it could be an issue in the rear view mirror. So I thought it wouldn't hurt to have a look. So I went to straighten the mirror prior to pulling it free when there was some clunking and cracking noise following which it became loose on the stalk. Something had obviously come adrift. I tried to pull it off the roof mount, before I could apply any effort the case fell apart. I was left with the ball joint swivel and the plastic plate to which it's attached. I removed it from the roof mount plate. Looking at the pile of bits I was left with one could see some broken plastic clips. Some of the broken bits were present. Others were not. So it was either never assembled properly or someone had been at it before (which would have only be a merc. dealership). The plastic is of a type which cannot be repaired by normal solvent bonding. Really it's fair to say it cannot be easily repaired.

Examination shows that the design is rubbish. The ball swivel is clamped into a plastic socket. There appears no lubrication. Over time (and I've not moved the mirror for probably 16 years) the plastic socket sets itself to the form of the ball. So when it's moved it applies leverage (which the design so adequately facilitates) to the mirror retaining plate and metal clamps enough to snap off the feeble underrated plastic retainers. The 'guts' are then all loose, including the mirror. This then creates pressure on the housing assembly and breaks any damaged or failing clips that holds the halves together. It might have been ok, but it seems my casing had two of the four clips already missing / previously damaged, the third broke away leaving just one which just unclipped itself. Lubricating and moving the ball and socket shows it grinding the plastic away nicely, but it frees up when lub'd and now moves with about 1/4 of the friction which it had when it caused the whole thing to self destruct. This is an appalling poor design. It is bound to fail.

Now for the bit that hangs down at the bottom with the LEDs. The mechanical design is mickey mouse. The casing is ok but what's inside is pathetic. Tiny plastic locator pins which negligable strength are suppose to position the guts so the various bits stay where they are supposed to be (noting some were bent and others broken suggests this was more by luck than judgement). Seems somone created the housing shape and the rest was fiddled around it to fit. The Japs must have spent the day laughing when they pulled one of these apart.

I thought Mercedes were quality. I don't any more.

 

[Jonssen]

So I repaired the rear view mirror and refitted it. Car still immobilised. Was reading elsewhere about the MBSS (Mercedes Benz Security System) which is fitted (windscreen pillar mounted interior sensors, siren under the bonnet) so I thought I might check that out as the siren on mine has always been turned off via its keyswitch. Turned on it functions normally (audibly blips) when I lock/unlock the vehicle with the IR keyfob, as does the alarm system if I open the boot or drivers door with the key (alarm set, obviously). It also gives an audible alarm squelch when I connect the batttery (didn't repeatedly fire off siren fully so as not to disturb neighbours). When finished, I turned the siren back off via the keyswitch, and closed the bonnet.

Turning on the ignition I still had the red/green LEDs flashing alternately. So I turned it off and then on again and noticed this time no flashing. So I tighted the loosly fitted battery terminal and attempted a crank. Engine fired first time and ran at tickover, not missing a beat. It ran for around 40-50secs then just stopped. Immobilised again. I tried repeating various things I'd done previously but it remains immobilised.

The only (possible) consistancy here is the run time of circa 40-50s is probably very similar the the time it ran when this first happened.

 

[Jonssen]

Well, to cut a long story short and fingers crossed, the problem turned out to be another faulty relay within the K40 module. It is, perhaps, unusual for relays which must have functioned for some 3000+ hours service to fail within an hour of one another (which leaves the remaining two normally powered relays as potentially 'suspect'). Similar to the first failure it proved erratic, only more so. On the board it appeared to meter ok, but then would only occasionally work with 12v on it sometimes going open circuit after a brief time, other times not working initially but then energising sporadically. I've since decided these K40s are far better without the cover fitted so one can see what's going on!

The RV mirror flashing lights, whilst possibly correctly indicating the vehicle is in a no-go state, are a bit misleading insofar as they suggest an immobiliser issue (lack of Drive Authorisation - DAS). I could not get any useful read from a 'blink code reader' suggesting that the 210 doesn't support 'analogue' diagnostics although there's a suggestion that some HFM-SFI 104 engines up to '97 should do.

I've not done a trace on this relay to see what it's actually powering, all I know for the moment is that it's an '87' circuit, so presumably one of the modules and perhaps something else. Life isn't helped by the fact that these K40s seem to be used and configured for all manner of things and finding a circuit drawing that is in any way accurate (or complete) seems particularly difficult, unless you are MB, I guess. Quite a lot of drawings suggest only two relays power modules and alike but in this case it's three.

I'm not sure who made these K40s for MB but they must have used a poor quality relay in what is a poor quality device. The copper bars which connect to the fuse holders are unsecured (how many are like that?) and that can result in both fuses not seated and fuses not contacting at all. See pics. So it you pull all the fuses, remove the cover before re-inserting so you can hold the bars in place!

Here's a separate post in respect of the rear view mirror repair:
https://forums.mercedesclub.org.uk/...ing-infra-red-rear-view-mirror-repair.184395/

 

[Jonssen]

Just a quick note to say that I decided to change all the K40 relays, save the horn relay. Although the other two were still functional I figured that as four relays were normally powered and two had failed, the other two might fail at any time. Sure enough by the time I'd removed them from the PCB they too had gone open circuit (presumably the heat finished them off despite me using lower temperature removal techniques on this occasion). Although it also got hot, as I was using hot air to get the surrounding two relays off the board, the horn relay did not fail.

Also re the fuses issue mentioned above, I noted that the K40 cover has some internal webs which which serve to hold the bars from coming too far away (once the cover is clipped into place). That seems a very cockeyed way of 'retaining' the bars to me but there you go.