'92 W140 How are these symptoms related?
 

Original symptom: Trunk lid handle did not retract.
Symptom #2: No interior trunk lights
Symptom #3: Back-Up Assist rods do not extend
Symptom #4: Vacuum-assist system closes trunk fully for roughly 20-30 seconds, then releases, trunk comes up 1/4"
Symptom #5: In complete sync with above symptom, front interior lights come on (at rear-view mirror)
Symptom #6: Symptoms 4 & 5 continue several times (6-7?) before finally stopping, seemingly giving up....trunk lid handle still not retracted.
Added notes: I attempted to retract the handle mechanically as instructed from the owners manual. It had an effect, but it never fully retracted. Problem is...now the auto-close mechanism seems to be disconnected from it entirely. Door closure assist seems to be working properly.
This is driving me insane, please help!

Several of listed items are related to a defective PSE (central locking) pump! It is under the rear seat on the passenger side!


ON the 1992-93 W140 chassis there is also a modification on the trunk pull-down so that it won't screw-up like yours is doing!

Did you try to reset your pump? I remember my 92 140, The drivers side door would jam about once every 3 months, the quick fix for me was to remove the fuse for the "close assist" system in the rear fuse block and then re-insert it. This would reset the pump and it would start working again. I had to have my door lock adjusted to fix the problem, I remember my pump being located in the trunk behind the trim on the drivers side between the gas tank and fender. It is behind the rear seat of the car. Try a reset and if that doesn't work your pump may have given out. Good luck!
Brian

Everything points towards the pump, it controls the lumbar, backup HVAC, the rods, lock and unlock, and the trunk handle. I think this also has a safety feature if it cant produce vacuum or pressuse it disables itself, pull the connector and wait ten seconds to see if it comes back to life. There was a service bulletin to modify the handle, but it required a new latch, some plumbing changes and the bypassing of a microswitch in the lid. This would drive the handle off the close assist pump. The lights coming on would indicate a fault in the locking portion, "thinking you have unlocked it"
The first thing would be to get a "mighty vac" tool and see if all the different diaphrams hold a vacuum. The pump provides pressure and also vacuum for lock unlock.

Thanks for all of the replies. My very first thought was to to reboot the systems by a complete power-down, which helps SO often with this particular car, but it comes back up doing the exact things. There seems to be some confusion (with me at least, and I believe others), there are two vacuum assist pumps: One under the rear seat and one in the driver's side trunk...by the amps and all. Correct? Which one controls the trunk latch and handle and the back-up rods. It is my understanding that the actual closing assist is the one under the seat, but the other functions are the other one....again, correct? No one has addressed why there are no trunk lights. How does this fit into the equation? If it were the closing assist pump, how could the doors be functioning properly? These pumps are expensive, so I don't wish to troubleshoot this by replacing them helter skelter.
In order to see why the handle mechanism is now disconnected I need to get the trunk lid liner off....any suggestions? It seems to be the typical MB "mystery attachments" that are the kind that snap off if you ever attempt to remove them. :confused: :confused:

I have the same problem on my S320, you will need to replace the PSE pump under the rear passenger seat. You may have accidently trun off the trunk light, there is a switch inside the trunk.

Jack

If I remember correctly, the trunk light is also on the number 9 fuse
in the trunk as the pump is, so check that fuse first.

syljua
W140 S320 1998

The trunk liner fasteners are two piece. The center round part will pull out with a flatheal screwdriver then the main plug can be pulled out.

I don't remember which pump controls what function. But I think the trunk handle closure is controlled by the pump under the back seat.

Sorry for the big gap in responses, but I was away from the forum with health problems, now resolved....hopefully. Turns out that I was remiss in checking fuses. I found #11 fuse in trunk fuse box blown. It is a 20 amp fuse marked trunk lights and something else....I'll get that info soon but I can't risk another blown fuse...you'll see. When I replaced the fuse everything, and I mean everything that was a problem suddenly was corrected....the trunk handle retracted, the lid sucked down tight, trunk lights were on, no flashing of the overhead (rearview mirror) lights going on and off, all door closure-assist working. Problem solved...or so I thought. I opened the trunk to verify that I had closed the fuse box cover....the handle extended, trunk opened......fuse blew!! I had no more spare 20 amp fuses so I used a 15 amp....again everything works great. My problem is that I know the next time I open the trunk the fuse will blow. What could possibly be causing this.....any ideas?? I thought perhaps a short to ground in the trunk light circuit, but if that were the case it would blow upon replacement. I need some expertise, please.