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1988 Mercedes Benz 560SL
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Discussion Starter #1
So I pulled all the injectors to send out to be tested. The guy I got my distributor from offered to do it for free. In the process I broke off these tubes on either side that connect to the seats of the injectors. They seem to be connected to the manifold so I assume they take vacuum? I've tried to google but I just can't figure out if nobody has asked that question or I'm using the wrong search terms. I'm trying to go through the vacuum lines and replace what I can and I've seen that quite a few are damaged, cracked and unconnected. I haven't found a master diagram for these things, only parts of it. A bit overwhelming to say the least
 

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1989 W124 260E
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1,692 Posts
Go to Google serch page and look to the right top you will see images .Click on it and in images search box put 560SL Fuel Injection Nozzele Holders . You will find a location on there i did .
 

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1988 Mercedes Benz 560SL
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15 Posts
Discussion Starter #3
Go to Google serch page and look to the right top you will see images .Click on it and in images search box put 560SL Fuel Injection Nozzele Holders . You will find a location on there i did .
I know where they are. I took the injectors out and broke the tubes in the process since they were so hard. I'm trying to figure out what they do
 

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1983 380 SL
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2,823 Posts
They just suck any stray fuel/fumes back into the intake. The injector holder has an "O" ring as does the injector itself. The injectors and the injector holder are held in by the spring pressure of the mounting clamp. There is no vacuum required operationally for the injectors... the vacuum tubes provide venting in the event fuel or fumes gets past any of the "O" rings.
At least that's they way I understand the function.
 

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1988 Mercedes Benz 560SL
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15 Posts
Discussion Starter #5
They just suck any stray fuel/fumes back into the intake. The injector holder has an "O" ring as does the injector itself. The injectors and the injector holder are held in by the spring pressure of the mounting clamp. There is no vacuum required operationally for the injectors... the vacuum tubes provide venting in the event fuel or fumes gets past any of the "O" rings.
At least that's they way I understand the function.
Makes sense to me. Thanks. Couldn't find any reference of it anywhere
 

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It’s also called air shrouding the injector. It was done to improve the atomization of the fuel mixture at part throttle when the injectors are least efficient. It was done to improve emissions.
 

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1988 Mercedes Benz 560SL
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15 Posts
Discussion Starter #8
It’s also called air shrouding the injector. It was done to improve the atomization of the fuel mixture at part throttle when the injectors are least efficient. It was done to improve emissions.
That's interesting. Here's something I found as well on a VW forum

Air shrouding was introduced to improve fuel atomization at idle, when the periods between intake air pulses past the injector are long. During this idle period the injector is still spraying fuel and with little air movement it does not remain atomized well. The air in the shroud comes from upstream of the throttle body where the air pressure is higher than in the intake, at the injector location, during idle. The air is directed behind the metal cap on the injector where it mixes with the fuel spray at a fairly high velocity to atomize the fuel and help it remain suspended in the intake until it is drawn into the combustion chamber.
Pulsed injection systems do not deliver fuel to the intake during the period between combustion chamber intake strokes so do not need to worry about the fuel remaining atomized for a relatively long time.
 
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