HELP .... 1986 300sdl fuel shut off wont release -- how to fix it ???

[netpro]

FINALLY after a long time of not working i replaced the vaccum pump on my 86 300 sdl and NOW when i turn the key off it operates the fuel shut-off valve to stop the motor ... but THEN it wont release it so i can start it again ... i have to manually put a screwdriver etc.... to hold the level open ..... so i can start it ...... becuz YES it has good vacuum and interestingly enuf once it has been running for a bit u can remove the " screwdriver and it will " stay " running ......

it's damn annoying to have to open the hood to stop or start the car grrrrrrrrrrrr

any ideas what may be causing it ???