I seem to have a similar problem - engine on 1989 300E frequently stops suddenly then will restart in about 3-4 minutes. I had been trying to figure it out for about a month when suddenly the car completely failed to start. After reading this post, I started looking into a possible relay problem. I discovered that fuel pumps are not getting any power. I hot wired power to the fuel pumps and the car runs fine. I've searched for the relay that you are describing and can find nothing with KICKDOWN on it. The one in the general area that you described has the part number 002 545 92 05 along with KR0003 KPR and 05 8956 68 stamped on it. There are two other larger electronic components mounted nearby. What do I need to replace...fuel pump relay, fuel control module?????