I have a 1989 300se mercedes and i am haveing trouble gitting it started any time it is cold i have to crank for at least five to ten min. once it is started it runs great down the road but it stumbles from a dead stop. I think it may be the fuel pump relay but I get voltage at the fuel pump for thirty seconds then it goes off also i get full voltage when i turn the car over. Another idea is could it be the cold start sencer or a fuel pump getting old and weak any help would be great.