get a miti-vac or similar device that has a handle you can sueeze to create and then measure vacuum. Then, connect it directly to the vacuum operated device on the very end(rear facing) of the injection pump. The miti-vac should be able to shut off an idling engine this way. If it does, this is OK. You may have a vacuum leak under the dash, like the hoses going to the ignition switch.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.