w123 turbo diesel runs away at idle. confused on what to check here besides the vacuum pump. if it sits in traffic it will just rev itself up for no reason. I was going to check the vacuum pump and take it apart and see if the diaphragm are cracked

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Will it turn off with the key ?

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Cracked diaphragm will usually cause you to lose your brake booster power.. very dangerous because it can happen instantaneously without expecting it.. heading towards a stop sign...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

"Run away" normally means the engine will scream its head off running on oil vapours...
What exactly is your engine doing? What revs does it do when doing it? In gear, running temperature? Need more info...(I can sit in traffic with the engine off )

And may I ask why you believe the vacuum pump could be doing it?

Perhaps an idle speed adjustment was done with the throttle linkage and once the engine is warmed up the idle governor can't control the idle any more as essentially the throttle is being pressed down slightly...

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

If the diaphragm is bad, then the oil can get sucked into the intake, and act as extra fuel.

I'm assuming his question has to do with a fluctuating idle, not a run away condition.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

It was way back around 2007 but I believe it was said back then that if the Rack Damper/Idle Pin is run in too far and or the Idle is adjusted to far it you can get the uncontrolled acceleration.

The reason for that was stated that the idle and high rpms are under the control of the Governor. If the throttle is pushed beyond the Governor regulation with what adjusts the idle you take it off the Governor control
.

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84 300D, 82 Volvo 244Gl Diesel

I'm not sure about that, given the VP outlet dumps into the crankcase which is full of oil vapours anyway, and there should an oil separator between the vent and intake.

Edit: And of course the .95x engine never had VPs with diaphragms anyway AFAIK

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

Hey guys. I'm working on the 300D tomorrow. All I know is it revs up at idle in traffic and revs very high. Injection pump hasn't been touched or adjusted as far as I know. ALDA is adjusted.

Not sure if it shuts off with the key. I believe it's an 84 300D.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Have you seen the car yet? It sounds like you are going off someone else's description.

Forget the vacuum pump. Some people are thinking of a gas engine which can rev high due to to an intake vacuum leak, such as a torn brake booster diaphragm. Not the same in a diesel which has constant atmospheric pressure intake (no throttle plate, actually a few do but for other reasons).

Perhaps the vacuum shutdown valve at the rear of the injection pump was replaced and installed incorrectly. You are supposed to slide it in tilted so the L hook goes in past the lever it pulls on to stop the engine. If someone just forced it in straight, that would push the lever forward increasing idle speed. Find out if it stops with the key, and if anyone has fooled with that part.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

yup, has happened to my w116 300sd. Little adjustment takes care of problem