My 1980 300SD has a new problem where it won't always shut off when the
key is turned off. The main symptom is that if the car has only been
running for a short time, like from cold start to a couple of mins, if
the key is turned off, the engine keeps running. After maybe 15-20
secs, it finally stops, but even then it takes another few secs for it
finally to quit. If it's been driven for 5 mins or so, then it usually
shuts off normally, or at least a lot faster.
I know the engine shut off is vac driven, so my first thought was maybe
the vac pump was going bad. I've also noticed that I hear a click from
the AC system maybe 1 min after driving off. I think this is one of
the vac gizmos kicking in that then allows the AC system to operate. I
think this click and action used to occur almost immeadiately on
starting the car, so this may be another indication of lacking vac.
I disconnected the main vac line at the vac pump. I didn't hook up a
gauge, but just holding my finger over the opening, it felt like there
was significant vacuum. My next step will be to try hooking something
up so I can apply vac to the injector pump directly to see if that will
stop it, to rule out that. Then with a vac gauge, I'll start working
through the sys looking for a leak.
Just wondering if anyone has seen this before and knows where to look.
I guess one possiblitiy would be the vac control on the ignition
switch. Also, if anyone knows what the vacuum measurement should be in
the main line going to the vac pump, that would be helpful.
TIA for any ideas.