Hello,
shut off valve won't fully engage shut-off seems to work OK but won't turn the last dgree to fully engage shut-off. It only slow the idle. Any Ideas what it could be. diaphragm seems to be OK.

Vacuum leak somewhere up the line most likely if not then the shutoff valve is starting to go. They're not expensive and pretty easy to replace (although IIRC it's a bit fussy due to the tight space). Try shutting it down with your mitivac connected and if it shuts off properly and holds the vacuum it's probably a leak futher up the line. Trace it back toward the pump and eventually you'll find it.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

Is there an echo in here?

Does your brake servo assistance feel ok still ?.

My other halfs 89 603 decided not to shut off last week,the diaphragm checked out ok (long nose pliers got the original pipe off and a bit of clear pipe on to test without to much hassle)

Turned out to be the rubber connection was split where it plugs to the main servo line at the front of the engine just above the belt tensioner.

The engine had started to take longer each day to shut down until as yours it would not stop but just idle lower,locking the doors had no effect.

An 89 300D has an electric central locking pump.

Sixto
87 300D

It's an 87'

No wonder that trick of trying to lock the doors had no effect then

An 87 foot what?

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Gone to the dark side

- Jeff

I was responding to Murkybenz. An 87 300D also has a separate electric central locking pump. And about 87 feet of vacuum line

Sixto
87 300D

my car did the exact same thing when the shut-off device went bad. did you test the diaphragm with a vacuum gauge?

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punkinfair

Don't even need that. Disconnect the hose, push down the stop lever, hold your finger over the nipple, release the lever. If the lever stays down, the diaphragm is good.

Sixto
87 300D

I seem to be having the same shutoff valve problem.
I tried the vacuum pump test method and would not hold 100 mbar and would settle down at about 50 mbar.
Then I tried the Sixto method listed above - pushed the stop lever down all the way and the stop pops up half way immediately , then gradually continues it's trip the rest of the way to the run position.

So I need to replace it, and I have found a 602 and 617 DIY on replacing the shut off valve - anyone know of a 603 DIY or is the 602 close enough?

And , is there a true sure-fire way to test if you got the valve in correctly without starting the engine??/?...
Thanks

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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602 method is close enough.

To test the installation, loosen an injector line, hold down the stop lever, crank the engine. There shouldn't be fuel squirting from the loosened fitting. It's not absolute but it's more than you'll know otherwise without removing the IP side cover.

Sixto
87 300D

Sounds good to me.
If however fuel is squirting from the loosened injector line is there a chance the beast will start - at low idle hopefully?
I guess that would indicate that the shutoff valve is not installed correctly.
I have also read a thread were someone with a 603 installed the shutoff valve incorrectly, damaging the IP and had a runaway situation.

I wonder how this occurs where you could damage the IP and how the incorrect installation of the valve causes a wide open throttle.?

Thanks Sixto for the reply...

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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If fuel squirts, review the installation.

Crank the cold engine with the glow relay disconnected and a mouse pad over the turbo air intake and loosen all 6 lines. The engine can't start. Shove some bananas in the tailpipes if that's not enough

I don't know how an improper installation causes a runaway engine. Maybe the shut off actuator plunger pushes the rack to full load. For me it has been sufficient to see the stop lever react when I apply vacuum to the newly installed actuator.

Sixto
87 300D