You should have 2 vacuum lines going to a Vacuum Switch on the Steering Colum Lock. On my 84 300D there is solid brown line and a brown line with a blue stripe.

On mine the solid brown line is the vacuum supply and goes into the top nipple of the Vacuum Switch on the Steering Colum Lock and the Brown with Blue Stripe goes from the bottom of the vacuum switch to the vacuum shutoff on the fuel injection pump.

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84 300D, 82 Volvo 244Gl Diesel