Ok, since your pump is making good vacuum, there is a leak somewhere else. Disconnect all the other vacuum consumers (locks, climate control, trans, egr) and plug the rubber connectors with golf tees. You should then be able to start up and shut down properly. If that works, then use your MityVac to track down the leak.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References