I had the same thing happen. It is most likely the vacuum switch in the dash leaking. Pull off the line to the shut off valve and stick your vacuum gauge on the line. If it pulls any vacuum you have a bad switch. Once the car shuts off, the vacuum is released letting you start again. The shut off lever should not be moving while the engine is running. It should move when you shut the key off.

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Current
Monika '74 450 SL
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FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
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'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf ‘86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
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