1987 420SL keeps cutting out

[martinswatton]

My 87 420SL which has covered 217k has developed what I think is an electrical fault. It occasionally cuts out when I have come to a halt for say traffic lights but now it is cutting out driving along at any speed. It wont re-start until I leave it for about a minute then it will start and drive normally. I am sure it is electrical because it doesn't faulter before cutting out as it may do if it were a fuel problem. Has anyone experienced similar?
I have taken it to a garage but the nature of an intermittent problem has made it very difficult to diagnose.
Any help much appreciated
Martin

 

[meanie]

Remove the crank position sensor & check it for cleanliness first.Also,check for corrosion behind the EZL unit.
As you say,this will be a difficult diagnose,as these early systems do not store fault codes.

 

[television]

Hi martin and welcome with your not so easy fault.

As meanie possibly the crank shaft sensor, when it cuts out do all of the dash lights come on immediately.

The crank shaft sensor could be put into boiling water and measured, it should be 1k ohm when good, £47 from Bosch service centers.

The fuel pump relay can also do this, remove the relay and bridge pins 7 and 8 to see it runs OK, if this cures it, just re solder the relay inside

 

[martinswatton]

Many thanks to you both. I'll take your suggestions to the garage tomorrow
Cheers

 

[martinswatton]

87 420Sl cutting out

Hi Malcolm

I thought the problem with the intermittent cutting out had been cured when the garage checked all of the connections but it's back again! It went 318 miles before cutting out again and now it's cutting out much more regularly. You asked whether all the dash lights come on when it cuts out - and yes they do. If I leave it for say two minutes it will start again and drive normally. (I don't whether that helps with the diagnosis?)
You mentioned in your response to my query that it may be worth replacing the crank shaft sensor and that Bosche supply them for £47. The garage tried the local Bosche centre and they quoted around £127 and the Mercedes dealership quoted £87 - is there a particular centre that you can recommend?
Many thanks
Martin

 

[martinswatton]

Hi Malcolm

I thought the problem with the intermittent cutting out had been cured when the garage checked all of the connections but it's back again! It went 318 miles before cutting out again and now it's cutting out much more regularly. You asked whether all the dash lights come on when it cuts out - and yes they do. If I leave it for say two minutes it will start again and drive normally. (I don't whether that helps with the diagnosis?)
You mentioned in your response to my query that it may be worth replacing the crank shaft sensor and that Bosche supply them for £47. The garage tried the local Bosche centre and they quoted around £127 and the Mercedes dealership quoted £87 - is there a particular centre that you can recommend?
Many thanks
Martin

 

[gaunty]

Don't know if it is helpful, but my car had very similar sounding symptoms - my local Merc specialist diagnosed this as the ignition module - replaced with a second hand part - problem gone !