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1982 300SD Turbodisel
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Discussion Starter #1
My door locks, fuel flap and near all vacuum components are in need of attention. During my troubleshooting I discovered that there is an electrical vacuum pump in the trunk, I thought all vacuum was supplied by the engine pump. Can someone explain to me what is the function of this pump and under what parameter it operates. It is very difficult to troubleshoot something you don't know how it's suppose to operate. For example: are all locks vacuum operated (I don't see any lines going into the front doors).
 

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'08 E63 AMG Wagon. C280 (320) track/drift slag. Wife has CLK500 Convertible
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1,029 Posts
Central locking pump...

Different circuit to engine vacuum functions.

Operates from switch in lock bezels to all door locks, trunk and fuel filler.
 

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1982 300SD Turbodisel
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27 Posts
Discussion Starter #3
I'm sorry but at what point is this thing suppose to come on. I have turned on the car and it doesn't seem to run. Also...is this completely separate from the engine side that runs the tranny, etc?
 

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the pump in the boot is nothing to do with the engine or tranny and only works when the doors are locked / unlocked.

In cars which have the orthopaedic seats, the pump in the boot also supplies air to the backrests of the front seats....in those cases the pump runs when key is in position I and lumbar adjustment is made via a switch on the seat belt buckle.


talbir
 

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1982 300SD Turbodisel
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Discussion Starter #5 (Edited)
How does this all come together when the system works properly. I have always locked the doors manually, and the fuel flap... I have to open the trunk and then pull the lock mechanism under the covers to open it.
The pump does not come on... traced it to the switch on the driver side door... there appears to be no DC voltage to the switch with the car on.

At this point suggestions would be greatly appreciated.
 

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The pump runs only when the lock switch is triggered by turnng the key. My 1980 did NOT have a vacuum/pressure line running to the driver's door since that lock triggered the central lockng so that connection was a simple mechanical rod. There s only 1 line since the system either sucks or pulls to activate each bellows. The pump is desinged to run for a few seconds until pressure or vacuum is achieved or the timer runs out (system failure). First thing to look for is does it run? That is electrical or a failed pump. Then when you get it running check the lines. All it takes is one to unhook and the sytem fails.
 

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1982 300SD Turbodisel
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Discussion Starter #7
Thanks

NordRhein as u mentioned the pump only runs for a few seconds and then shuts off. So I missed it at the beggining, I took off the the driver side door actuator and on my 82 300SD and there is no vacuum line only an electrical line that completes the circuit for the vac pump. After a few trials and errors, I finally narrowed it down to the vacuum actuator on the passenger front door.

Everyone thanks for your help.
 

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300SD
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What you guys did not mention is that there is a vacuum reservoir inside the right front fender (must remove the fender to see it). It stores the vacuum to keep the vacuum door locks operational for a day or two after the car is turned off. 123 chassis cars have this vacuum reservoir mounted in the trunk, under the rear window shelf. of course, 123 cars do not have a separate electric vacuum pump for door locks only.

I think most of these trunk mounted air pumps burn themselves out when a leak develops int he system. They do not seem to have a shut off mechanism to save them from self-destruction if there is a leak in the system.
 

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w126
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The vacuum pump does have a timer. I think the 126 did have two versions of the pump. Maybe that's a feature of the later pump.
 

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1982 300SD Turbodisel
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Discussion Starter #10
Well I will check back and let you guys know how it all turns out. I do need advice on where I can get the vacuum actuator for the passenger door.
 

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86 560sec-168K -Ext. Light Ivory/Int. Black/01 E320 4Matic Wagon Brl Silver/Black/ Mad '95 Q45
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where in the trunk is the pump ??
 

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2015 ML 400 x 2
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Lift the spare wheel cover, on the right by the rear panel under a triangular piece of dense black foam.
 

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86 560sec-168K -Ext. Light Ivory/Int. Black/01 E320 4Matic Wagon Brl Silver/Black/ Mad '95 Q45
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420 SE said:
Lift the spare wheel cover, on the right by the rear panel under a triangular piece of dense black foam.
Cool found it - did not go on - i bench tested it and got it to go on a couple of times but intermittant - took it apart and when i manually triggered relays worked but kinda weak -- lubed the motor and it died. --
i have no leaks in tubing, car running doors shut , i sucked on tube - went to open door and was shocked it was locked -- took 10 seconds to realize what i did -- blew into tube and locks opened --- good way to break into car if trunk open:big laugh:
Also the green wire in the 3 wire plug was spliced and 2 wire attached and ran thru trunk into car by the upper driverside back deck - was not able to trace it further ??? any ideas......................
New pump, yes - what else could be up or u think just pump???
 

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2015 ML 400 x 2
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From your description, it sounds like you are going to be getting a replacement pump!
 

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86 560sec-168K -Ext. Light Ivory/Int. Black/01 E320 4Matic Wagon Brl Silver/Black/ Mad '95 Q45
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420 SE said:
From your description, it sounds like you are going to be getting a replacement pump!
Got one on the way- next week.
Antenna help check out my other thread
Any idea what the green wire on pump is ?? and why there would be a splice in it ???
 
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