Our 1983 300D won't turn off - the only way is to open the hood and manually stop it.
We assume from viewing other posts that this is a vacuum leak issue???
Does anyone have clear instructions (preferably with diagrams) on how to isolate and fix the leak(s)?
Thanks in advance.

if you have the car running try to find the hissing/sucking sound. Trace all your vac lines on the engine look for worn/torn rubber boots etc, my major leak was the brake servo line but I dont know if your car has the same part

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

May be you can try my fix. I fixed it but never get to the bottom of it. Link below

300D will not shut off unless I blocked this line

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I just replaced the Shutoff Valve yesterday. Not horribly complicated, but you have to be careful installing to ensure that you get it installed properly. Improper installation could ruin an engine. There are many posts to explain the issue.

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This area is typically used to brag about one's current or former automobiles.

Their is an active post where his will not start. Yours will not stop.If you get together a comprimise for both of you might work.

Actually test for vaccum presence on the shut off line when you shut key off. If there get a mityvac type device and apply vacuum to the actual new shutoff valve with a short piece of hose. One or the other will be bad. In place of the mightyvac on the shutoff. You can create enough vaccum to shut a normal shutoff valve off with just sucking on the tubeing.

I would start by plugging the lines for the door locks and the ACC under the hood.

Then take a mighty vac and check vacuum on the shutoff valve at the pump.

All the above takes about 2 minutes or less if you already have the golf tee's.

If you are still having issues, check the amount of vacuum you are getting at the pump. Then work from the pump towards the firewall. You should find the culprit fairly quick.

I found a couple vacuum elbows that were torn on the lines connecting to the ignition switch recently, along with low/erratic vacuum and a leaking brake booster.

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AJ

1985 300D (SOLD)