560SEL stalling when cold

[Thomaspin]

A couple of times a week my cold engine (this is NorCal cold, or 50F) will stall a few seconds into backing out of the garage. It has just 93,000 on the odometer.

I checked the archives and could not find any specific guidance except maybe that the overload voltage protection relay (OVP) may be faulty, but that usually seems to be accompanied by a non-extinguishing ABS light, a problem I do not have.

Any ideas would be welcomed. There are no problems in running or on warm starts.


Thanks in advance.

[downsmith]

Does the 560 have a warm-up regulator? A can of Gumout or an Italian Tune-up always helps, too.

[DJNEWK2]

You may want to consider replacing your cold start valve that supplies the engine with instant fuel for cold starts...I just replaced mine on my 560 for the heck of it but its an easy change out and it's only about a hudred bucks or so. That should basically cure that problem (hopefully)

Good luck!

Alan

[Thomaspin]

Thanks to replies from Donnie, Benzmac and Maurice dePiero, the following were suggested causes:

1 - Faulty coolant sensor (4 pole on the 1990 CA 560SEL) - I checked the impedance against the chart in the MB manual, and it was OK but at only $12 I replaced it anyway. You need to remove the filter cover to gain access - it sits right behind the cold start valve and requires a 22mm deep socket for removal. Still stalls.

2 - Sticking idle air control valve - that's the 4" long cylinder just in front of the air filter cover with a 2 pole electrical contact and two large rubber air tubes connected. I removed mine and checked for easy sliding of the piston - you can hear it when you tilt the valve. Mine was fine but I cleaned it with carb cleaner just in case. Still stalls.

3 - Removed and replaced the fuel pump relay (same part re-used) after cleaning contacts - it sits on the fire wall on the driver's side, just to the left (facing engine) of the red over-voltage protection relay with its two 10 amp fuses under a clear cover. Stall cured....so far.

Thanks to everyone for their help.