Was helping a friend/fellow member troubleshoot the vacuum issues on his '82 300TD so during testing I isolated the ignition vacuum lines (brown w/ stripe) from the rest of the vacuum lines so I can manually hook up the ignition vacuum line w/ a MityVac to test if it was indeed the noise he hears in the dash when the engine is shutoff.
While the engine was running with ONLY the ignition switch vacuum line disconnected from the system and hooked to the handheld pump, the idle was much lower than when it's connected (~550RPM). Essentially the brown striped line had NO engine-supplied vacuum when the engine was running (I was not pumping on the handheld vacuum pump). Prior to this, with the brown line attached, it idled properly (~750RPM).
Does this mean that the vacuum input on that brown striped line is required for proper engine idle speed? I'm thinking it has to do with the shutoff valve at the back of the IP, but not sure why.
To give a heads up, the shutoff valve has been replaced recently. Central locking system held vacuum. Climate control system held vacuum. Ignition switch system (to switch on tumbler and back out to engine bay to the shutoff valve) had small slow leak when engine was shut off confirmed by two MityVac units plumbed directly to ignition vacuum switch line (brown w/ stripe).
Also, and a secondary question - regarding the vacuum operated ignition switch beside the steering wheel - if you turn the key FAST to shut off the engine, it would shut off quicker. But if you slowly turn the key, it would remain running and shut off a few seconds later.
Does this combined information confirm that the leak is in the ignition vacuum switch?
01-07-2011, 02:39 PM
Linear Mode
