S420 PSE door locks retraction of trunk handle inop
 

Does any one have experience in testing the (PSE) pneumatic system equipment, 1995 S420 W140. I am referring to the central lock pump also used in lumbar support and retraction of trunk handle and open and close fuel gas cap cover. This pse is located under the rear seat passenger side. Aside from the electronic computer test, is there a manual testing procedure you may be familiar with?

Since there are, two pumps do not confuse this pump with the door closing assist pump located in the trunk.

Thanks

RE: S420 PSE door locks retraction of trunk handle inop
 

yes i have alot of knowlege of the system. do all the other functions of the system work? if not there is a hose inside the pump that popes off this will cause the whole system to shut down so if other components of the system are working this is not your problem. try vacuum testing the element on the handle if its leaking replaced it.

RE: S420 PSE door locks retraction of trunk handle inop
 

Well, welcome to the drama.

Here's the skinny. As it has already been referred to, there is a red hose inside the pump box that is reportedly a problem with popping off, as well as, having small fractures in the hose, etc. Do not attempt to replace the hose if you have no experience with it. Other problems with the pump, such as what I've recently experienced, is that I can hear the pump activating when the doors unlock (which means the pump is pushing the air, but it will not pull the locks down). In other words, the pump is not reversing (if I'm saying this correctly). The bottomline is this my friend, you need a new pump. This is the bottomline! Sleepwalker tried to tell me this, but I had to spend $50 bucks to find it out for myself, just to be sure, because certain characteristics just didn't make sense. The pump just acts strange, and does strange things when it wants to. So, it is definately the pump. Either replace it, or have your current one rebuilt. As for me, I having mine rebuilt. It only costs $249.00 to have it done. So, this is the best option, because often times you get a better pump back!

Hello. I have a similar problem regarding the pump. But I am unclear to which pump it could be. My doors will lock and unlock. Along with truck handle popping out and in. But the closing door assist isn't pulling the doors in nor the trunk down after closing. Can anyone tell me which pump it could be? That's problem #1. Now #2. My rear door is closed and will not open. The lock goes up and down but the door will not open. Does anyone know what this problem could be? And how to open the door. HELP...

The pump you are looking for is the one in the trunk on the left side it closes the door and pulls the trunk down

pump box
 

Sounds like my problem. Where is the pump box on a 1979 450sl? Is it a vacuum or pressure. I'm assuming it operates electrically through a fuse and relay. Is there documentation for research?