S500 coupe cuts out after 20 mins

[JamesP]

Hi there, got a problem with my S500 W140 coupe. She starts fine, and smooth as anything drives for about 20mins then just completely stops, like the ignition has been turned off. So, put it in park, switch off ignition and turn it over, usually starts after the 5th or so turnover and is fine again. If it doesnt start i wait 5 mins then its ok. By this time of course i high tail it home again! Recently had the crank shaft senson changed... any thoughts?

 

[jibcl500]

has the engine been power washed at all recently, what year is your CL

jib

 

[JamesP]

no, i never clean under the hood... its a 1995, august

 

[jibcl500]

so yours is like mine then, no distributors, do you have any lights come on on the dash?

jib

 

[JamesP]

i think it might have distributors actually, because they were all checked when the crank sensor was changed, its the older S version pre CL.. no lights on the dash, apart from when it cuts out, then they all come on, like when you first start it..

 

[jibcl500]

was the crank sensor changed as a result of this fault, if so the crank sensor is still at fault or wasnt replaced. If the sensor fails the engine wont know where to take a reading from hence the shut down.

Is your milometer digital or the old style roll over numbers, if the later than it could be the ignition module, these fail after about 0-15 mins once hot.

jib

 

[eric242340]

Hi there, got a problem with my S500 W140 coupe. She starts fine, and smooth as anything drives for about 20mins then just completely stops, like the ignition has been turned off. So, put it in park, switch off ignition and turn it over, usually starts after the 5th or so turnover and is fine again. If it doesnt start i wait 5 mins then its ok. By this time of course i high tail it home again! Recently had the crank shaft senson changed... any thoughts?

It sounds like the EZL unit is failing (but based on the information so far) its difficult to tell. Do you have an idle speed problem also? The crankshaft position sensor is connected directly to the EZL control unit, and these two problems are often diagnosed wrongly. Often the Crankshaft position sensor diagnosed as the cause and all along its the unit it is connected to, the EZL control unit. The idle speed is the clue to this.

 

[JamesP]

Milometer is digital, and there are no probs with idle speed. i start it once a week or so just to keep it running and the air con turning over and she ticks over very smoothly, just changing now and then as the air con cranks up a gear. i keep thinking battery?

 

[JamesP]

The sensor was replaced at christmas by a merc specialist. it seemed to solve the problem but just before i collected it they took it out and it cut out on them. So they kept it for another week trying to get it to fail again and it didnt. it was then fine for 6 weeks until cutting out once more and now does it every time...

 

[jibcl500]

No not battery, the battery would have to be really buggered to cause the engine to stall.

OVP relay???? Eric

jib

 

[JamesP]

the guy i got it from (a merc classic specialist) suggested the ovp relay but the people who did the crank sensor said mine didnt have an ovp relay

 

[jibcl500]

Malcolm will know if the w140 Coupe has the OVP relay. have you had this problem since you bought the car from the specialist?
jib

 

[jibcl500]

sounds like ignition module failure, I had a w140 s500 on a 1993 k plate, ran great for the first 15 or mins and then died, had to wait 15-30 mins before a restart and then died again 15 mins later.

Module sits under the plastic cover on the right side on the inner wheel arch inside the engine area, search Ebay they come up sometimes, MB ask about £1000 for these from memory
This is on ebay, its not the correct part but it gives you an idea of what to look for inder the bonnet, check your connections.
http://cgi.ebay.co.uk/BOSCH-IGNITIO...ryZ10398QQssPageNameZWDVWQQrdZ1QQcmdZViewItem



jib

 

[JamesP]

to be honest, i have had nothing but problems with it from the start, despite going to a specialist and paying way over the odds. this problem started just before christmas, the crank sensor replacement seemed to fix it but clearly not for long! what i need is somebody who really knows them, but that is easier said than done. The people who changed the crank sensor said they didnt want to see it back..

 

[jibcl500]

Think its time to name and shame the specialist!!!!!

Where are you in the UK, some one here might be able to provide details on a specialist in your area.

Can you clarify for me that you have ignition HT leads running to both sides of the engine at the front, 4 per side and one running down to behind the headlamp to the coil pack.

jib

 

[JamesP]

I might get sued!! Just checked but i cant see any leads, everything is covered. There are two big plastic covers at the front, one on each side and i can see some leads running behind those..

i am in south east london... the person i bought it from has recommended a specialist he uses but they are miles away and i cant risk driving it...

 

[television]

James your car does not have an OVP relay and it would not cause your problems if it had.

You must feel sad about the whole thing. What is the car a 140 051,050 or 070

 

[JamesP]

its a real shame, because when she runs she is amazing, and in remarkable condition, outstanding. but i have been so upset with the whole experience of owning i am tempted to scrap it completely and start again. i did lots of homework and thought i was sensible paying around 3k over the odds by going to a specialist seller too, clearly not enough!

 

[jibcl500]

so your engine bay looks like this then.

jib

 

[JamesP]

its a W140 070...