my 79 300d is not shuting down. I thought it was the vacume shut-off valve. i pulled it out and sucked on one side, air passes through. when i push on the pin it stops the air flow so i asume it is working. I tried blocking the vacume lines for the doors and what ever else come off of the three way spliter and manualy pushing the pin on the vacume switch ( i pulled the hoses into the engine compartment and re-attached the switch) but nothing happed. when I use the manual shut down, it really dose not want to die. what am i over looking?
thanks,

STRESSED