Intermittent starting C240 1998

[stargazerplus]

I have a strange problem with starting my C240. The problem is very intermittent and has me pulling my hair out!! (What little there is left )

First off it has autostart, you know when you flick the key the starter continues until the engine runs.

The battery is maintained with a conditioner and the conditioning test puts the battery in the strong category.
It has had all the 12 spark plugs replaced about 10k miles ago.
It has a new Crankshaft Position Sensor and MAF meter.

It usually fires and starts immediately when the car is cold after leaving it overnight and when it is hot, but not always! 9 out of 10 times maybe!

After sitting for 7 hours at work it fails to fire, maybe 6 out of 10 times and when it does start it seems to "miss" for about 3 - 5 seconds then runs absolutely fine.

I would be delighted to find out what is wrong. I am tempted to take the car to a dealer to have a diagnostic run, but am a bit concerned that no faults will show up as the probelm is so intermittent... it does seem to be getting more and more frequent though.

Any advice much appreciated as this is driving me round the bend!!:evil:

 

[Blobcat]

I wonder if this is plug leads? I'm sure this has come up previously with a 240

Here it is; http://forums.mercedesclub.org.uk/showthread.php?t=21603

and here; http://forums.mercedesclub.org.uk/showthread.php?t=17650

 

[television]

If you care to put up the first 9 numbers of the VIN I will do a specific search later in the day.

Malcolm

 

[stargazerplus]

If you care to put up the first 9 numbers of the VIN I will do a specific search later in the day.

Malcolm

Thanks Malcolm! I really appreciate this but can't find anything specific in WIS troubleshooting apart from a dodgy fuel filter pressure valve that might account for the problem!

The chassis number is W2020262F744***

I am loathe to believe it is the plug leads as there is absolutely no misfiring once the engine has caught and settled! The idle is perfect also after the initial shaky start once it does start.... I am inclined to believe it is a temperature fuelling issue as it always seems to be worst 6 - 7 hours of standing! Is there something on these engines like a cold start injector which is temperature controlled? Problem is that it usually always starts immediately after an overnight sit.

 

[television]

Thanks Malcolm! I really appreciate this but can't find anything specific in WIS troubleshooting apart from a dodgy fuel filter pressure valve that might account for the problem!

The chassis number is W2020262F744***

I am loathe to believe it is the plug leads as there is absolutely no misfiring once the engine has caught and settled!

I wonder if it could be a dry joint in the ECU this could be a cause for a heat/time related fault, anyway see what I can find.

Malcolm

 

[stargazerplus]

Where is the ECU on this model?

 

[television]

Where is the ECU on this model?

I could well be wrong here, I thought it was bolted to the firewall, and it was this that could cause some of the problems you are having, the firewall acting as a heat sink. If yours is there, the problem was that the output devices had a silicon paste on them to disipate the heat where they were attached to the firewall.

Its 161 in the pic

http://www.detali.ru/cat/oem_mb2.as...GM=717.464&CT=F&cat=44V&SID=54&SGR=080&SGN=06

malcolm

 

[stargazerplus]

The ECU is in a lidded black box with a separate fusebox in the well behind the engine on the passenger side. Took it out this morning and cleaned the contacts, reseating the connectors.

I also looked at the CAMSHAFT position sensor (as opposed to the crankshaft one) and was amazed to see that it was rather filthy, covered in a dry hardened black greasy film. I am doubtful as to whether this would make any difference but I have cleaned and reinstalled it. It looks very different from the Crankshaft one but I presume that this too works on magnetic flux principle??

We'll see how it goes, although I'm not holding my breath!

 

[type49]

Crankshaft position sensors do fail, although usually when hot.