Put a vacuum line to the shut off valve and give a couple of strong sucks on it before condemning the valve. It could be a vacuum leak elsewhere.
A really frugal person might figure out how to disassemble the valve and repair the tear with Goop or something.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

..........PEH..........

First thing that popped into my head also.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

He'd use goop on a cracked cylinder head..........

You could just buy a nice mity vac and run a length of vacuum tubing into the passenger compartment. Pump it a few times and you're golden. Plus you get to buy another tool, one that will help you track down your other vacuum leaks from re-using old vacuum fittings.

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1985 300D Gretchen (Astral Silver) 220k
1983 240D 4-speed Evelyn (Orient Red) 203k


TANSTAAFL

The gold will quickly turn to stone if the diaphragm is ruptured.............

If the guy is frugal enough to want to repair the diaphragm, he aint going to want to buy a Mity Vac. He needs to use his god-given Mity Vac found in his cheek muscles. If he gets desperate he should be able to insert a small vacuum guage in one side of his mouth while sucking on the vacuum line in the other.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

This is very good advice for someone wanting to minimize repair costs... before you replace the valve, be sure it is broken!

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

This is about the very first advice given concerning the car not shutting off.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Us Mercedes diesel owners are suckers, in a way?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked