I had to replace my w124s vacuum pump today, it made a nasty noise on my way home from work. I had a used one off my donor engine and put it in. I looked at it inside, it had a number "3/1" inside the case. Does that mean its the updated style?

The engine always hesitates to shutoff and me and my buddy observed the shut off valve is very slow to shut off. It did this on the old car before the swap and after. Bad shut off valve on its way out?

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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

On the new style pump you can't see the ball bearings.



It could be a tired actuator or weak vacuum. A couple of quicks pulls of a MityVac directly on the actuator should stop the engine. If it passes, look upstream. Could also be base idle is too high.

Sixto
98 E320s sedan and wagon

Did you prime the pump?

I did not... it's the first time i replaced a vacuum pump. Why should I have done that and how bad is it that I didn't?

The idle is too low. Somewhere Along the line, some genius cut the wires to the ELR two prong connector on the back of the IP from the positive harness. I actually have to repair the two wires. What would cause weak vacuum? This pump seems to produce strong vacuum.

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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

Old Cracked EC (Engine Compartment) [subject to almost constant engine heat] Vacuum components MAY LOOK GOOD ... BUT !

http://www.w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/07.1-0500.pdf
The OM602.962 is on page # 10

Is there not a Manual idle adjustment that is set before the elr takes over ?

http://www.w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/07.1-1100.pdf
OM602.962 Manual Idle Adjustment procedure begins on page# 7

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'84 300SD sold
124.128

You can adjust the idle up using the mechanical idle adjustment until you fix the ELR. It's a hex screw with a locknut horizontally right up above the ELR connector. Loosen the locknut, turn CW a turn or so at a time until you get to 650 RPM or so.

Regarding the vacuum situation - the vacuum pump you pulled from the working car already had oil in it. I doubt the lack of prime on a used pump would cause issues. How would it be any different than leaving it off for a couple days and restarting it? I don't see the difference. New pump, sure it needs a prime. Transferring from one engine to another, I don't see much of a point.

Weak shutoff is likely caused by a vacuum leak somewhere.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)