I have 1995 E300D Mercedes body 124 and have no vacuum at modulator. So maybe a hose is off but where is the SOURCE for the modulator vacuum? Help.

On the older models there is the Vacuum Pump and the Main Vacuum Line that has 1 or 2 nipples on it and the Main Line goes to the Power Brake Booster.

All of the stuff that needs Vacuum connects to one of those 2 nipples by way of 3 and 4 way rubber Connectors and of course that color coded Plastic Tubing.
Some modes have an Electric Vacuum Pump for the Locking System.

If your Emission Sticker is there it will show some of the Vacuum Lines.

On My Year and Model the Transmission Modulator is connected to a Vacuum Valve that is on the Fuel Injection Pump. Between the Tubing that connects the Vacuum from the Main Line to the Vacuum Valve on the Fuel Injection Pump there is a Plastic Orifice inserted into the Hose; meaning it is between the Main Vacuum Line and the Vacuum Valve on the Fuel Injection Pump.

There is also what looks like a Vacuum Line coming out of the Vacuum Valve but it is just a Vent line. In My case all of the Vent Lines have solid Black Tubing.

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84 300D, 82 Volvo 244Gl Diesel

I have gotten all kinds of answers but yours I think is right on the money. I figured the vacuum came from the injection pump. I will take off the crossover pipe today to verify what both of us think.

I thought the vacuum came off the power brake line but when I took the small line off that nipple, all I got was the engine turn off not working. Thank you again.