Hello All,

My car is a 300TD '84 grey market. I've been working on the vacuum system. So far I've found one bad lock actuator. The climate control puple line is also leaking...both these have been plugged until there is time to fix them. The priority item to fix is the hard shifting. There is '0' vacuum on the modulator black line when the throttle is just cracked open. I disconnected the vacuum regulator linkage and verified the vacuum is variable and correct at the '10mm from stop' setting. When hooked up again, there is no variable action with the throttle. The two plastic vacuum switches on the valve cover seem to be bleeding off all vacuum when the throttle is opened. This particular car only has two lines (white and black) going to these switches (no EGR). I've pugged the connector where the white line connects...now have variable vacuum, and the car shifts well.

Can someone explain to me the purpose of the valve cover vacuum switches? With the vacuum pump hooked to the white line, vacuum can be established only with the throttle either opened or closed.

Thanks for your help!

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