Hey guys i need some help with finding out why my car struggles to turn off. You can tell it cuts the fuel off partially cause it sounds like it wants to die but sometimes she will stay running and sometimes I'm lucky and get it to shut all the way down. Keep in mind my reading may seem low but I'm at 4500ft so roughly a reduction of 4.5" from sea level readings.

1st Pic- overall view of the routing of vacuum lines


2nd- with engine off I Plugged off yellow/brown line and applied vacuum to solid yellow line. Held vacuum fine. Did it the opposite way with plugging the solid yellow and applied vacuum to yellow/brown line. Vacuum held both times


3rd- with engine running I plugged the brake booster line at the end and plugged the first line where the grey/clear line attaches. I then applied vacuum to the middle line where the green line usually attaches. I found the vacuum to be around 20".


4th- with engine running I plugged both lines where the grey/clear and the green line attaches to the main vacuum line. I then applied vacuum to the end of the brake booster line and read 20". Isn't this high because i thought the reducer downstream reduces the vacuum a little before it goes into the brake booster?


5th- With the engine running I re-attached brake booster line and the grey/clear line to there normal positions. I then connected my mighty vac where the green line normally attaches and read about 8"

sorry for all the pics but i wanted to be as clear as possible.

6th- engine off applied 15" of vacuum and let it sit


7th- engine off after about 10 sec or so maybe less it leaked down to about 5" from about 10-5" the gauge was jumpy.


Could this be a bad shutoff valve thanks guys for the help!

In picture # 6 and #7 are you hooked up directly to the vacuum shutoff valve? It looks like it but it's not totally clear. If so, and you are finding that the vacuum bleeds off after about 10 seconds, I'd say indeed your diaphragm inside is probably ruptured and you need a replacement valve.

20" of vacuum from the pump is great.

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

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So if I'm reading this right, you're getting 8" with the engine running and the brake booster hooked up and 20" with the engine running and the brake booster line plugged, right? If so, that would tend to indicate a bad booster.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
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uberwasser- yea it hooked up directly to the valve and when I apply about 15" it drops to 5" in like 10 seconds and the gauge jumps down as well. I find it weird though that when the engine is running if i apply about 10" of vacuum i can shut it off but it still does bleed down to about 5".

Skippy- Im getting 8" with the brake booster line hooked up and the grey/clear line hooked up. My brakes are working fine could it be that reducer thats down stream of the brake booster?

Part of the problem is the 8" you're seeing when the grey/clear line and the booster are connected. There is a leak somewhere. You should be seeing 15-20" with everything hooked up and the engine at idle.

To eliminate a leak at the booster, hook it up again like you have it in #5 but leave off the grey/clear line and plug that opening. You'll be testing just the booster, then.

Assuming you confirm your booster isn't leaking then you know you have a leak in the branch that the grey/clear line feeds.

If you also then find that your shut off valve bleeds off vacuum then that it likely the leak source. A good shut off valve should hold vacuum basically indefinitely.

__________________
1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

In picture number three I have the brake booster plugged at the end with the grey/clear being plugged as well. i hooked up the mightyvac to where the green line should go wouldn't that be the same? here I'm measuring 20"