On my '95 S320 the trunk has developed a problem.
The handle does not pop out anymore and the close assist threfore does not work anymore either.
I have seen this happen once in a while over the past four years, but it always worked again. It now seems to be out for good.
The bad thing is I really have to slam the trunk closed to get it to close now.
How do I fix this?
Thanks,
Sab.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged

Today the entire central lock system seized to function.
The infrared and alarm still works , but no door locks, not even with the key.
I checked all fuses and they are all fine.
Please anyone give me some tips as to what is going on.
cheers,
Sab.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged

I am not an expert, but I can tell from the experience I have gathered from my cars:

The pumps that control the power assist systems and door locks on W140s are different (one for each system).

I doubt that both pumps failed at once. Anyway, the pump for the power closing aid on doors and trunk is the one that fails more often. Usually when it begins to fail you can trick the brain of the pump by pulling the fuse in the trunk compartment (not engine) and let it stand for a couple of minutes before reinstalling it. I think is #9 or #12, but don't quote me on that.

If the pump for the power closing aid fails completely, you can close the side doors with a somewhat hard slam without no problem. The trunk requires for you to fiddle with a manual override switch which is located near the lock on the trunk lid. This switch allows the lock post to lower about half an inch, hence you do not have to slam to hard the trunk to close. The manual covers this issue quite well, check on it.

About the fuses, EVEN if they seem OK to you, CHANGE THEM ANYWAY! They're cheap and you could be surprise. Remember to check BOTH fuse boxes on the engine compartment AND on the trunk.

__________________
A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]

Sab,

The symptoms you described, the random closure of the trunk, and failure of the central locking system were exactly the symtoms I experienced when I had a PSE (Central locking pump) failure. The W140 has two pumps - one in the trunk (door closure assist) and one under the rear seat on the passenger side of the car operates the central locking system, gas pump lid and lumbar support on seats. The pump you will need to replace is the PSE pump under the rear seat (passpenger side of the car) The item isn't cheap. You can find a new Bosh PSE pump on Ebay for $390 - dealer wants about $750.

Check the fuses as Rosich suggests. If the pump is working you will also hear a humming noise coming from under the rear seat location when the system is activated.

PSE pump failure is common in our model of MB.

Russell

The pump also has built in protection if it detects a leak in the system. If this is the case it can be reset by pulling the fuse out for a minute or so then replacing it. It will then work once or twice before it detects the leak again. (This was the symptom that mine showed before I replaced a leaking actuator.)

My advice; pull the fuse then replace, click closed the trunk latch catch inside the trunk to "trick" the system into trying to pull the trunk closed then listen for the pump. If you do hear the pump during this test, try looking for a leaking hose or failed actuator.

Good luck

Thanks for all the replies.

I did pull the three fuses in the trunk and the two in the front and reinserted. The pump did not come back on. I swapped all fuses relating to vacuum and central lock and no change.

So what I would guess from your responses is that my pump is bad.

BUT if I press the central lock button from the inside I don't even get the light on that switch. Would that be the case if the pump is bad? Or would the switch still light up when pressed and just no pump?

I would hate to buy a $400 item just to find out it is something else.

Is there any other way to test the pump under the rear seat?

Thanks,
Sab.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged

Sab,

If you are mechanically inclined, you can remove the pump from the rear, passenger side seat and test the pump's motor. After removing the pump's electricial connectors and the vacuum hoses, you can use a torx T-6 or T-7 (I can't remember) size driver to remove the bottom cover to expose the pump's motor. Connect the motor's wire's to a 12 volt source and the motor should run if it is working.

Attached Thumbnails

 

OK, removed the pump today and it seems fine.

Question:

Should the two switches ( door lock and open trunk) still flash when pressing even if the pump is bad?

I just have the feeling I don't get power to the pump.

There is a fuse up front (I beleive it's #6), mentioning door lock relay. Where is that relay and how would I test it.

God I wish I had a service manual. Can anyone send me some info on troubleshooting this darn pump system?

Thanks,
Sab.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged

I would do a search on this forum, and there are other forums. This subject has been addressed many times.
PS the red green lights can flash, that does not mean the lock unlock pump id doing its job. The lock and unlock also provides vacum/pressure for other things like the AC, lumbar, some headrests, and backup rods (early modls)

Sab, Peter is correct. The lights for the Central Locking system will continue to flash with a broken PSE motor.

Below are the id's for the vacuum hose relating to the PSE pump. Remember your car has both a PSE pump and Closure assist pump that operate different components in your car.

ZV Central locking (CL)
RH Backup assist (BA)
SFG Retractable trunk lid grip (RTG)
FKS Rear head restraint retraction (RHR)
P + Pressure connection
P - Vacuum connection

MB Tools and information are available to diagnose problems relating to the PSE pump, however due to the expense, I found it more cost effective to use the "home" mechanic method of finding the broken part.

PSE pump failure is common in your model MB and age.

Thanks guys,

the lights on my switches do NOT flash at all since the system failed. I have the feeling the whole system does not get power rather then the PSE being bad.

The only items not working are related to the PSE pump. Trunk handle door locks, lumbar headrest and no indication of any power on any of the related buttons.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged

I pulled the PSE pump out and dropped it off at a shop that will test and rebuild it if faulty.

The car does not start without the pump, it does not even try to crank over. It is just as if the anti theft is activated. I hope that is normal and there is nohing else wrong now.

cheers,
Sab.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged

SAB,

It is interesting your car will not start without the PSE pump installed. I ran my car without the PSE for weeks. Also, you can not rebuild the PSE pump. Bosh will NOT sell a replacement motor. If a hose has come loose in the PSE pump, I guess the hose could be reattached. I'm guessing there is something else going on in your control module causing problems.

Cars made after 1/94 - PSE pump provides negative return to the starter lock-out relay. To start the car you need to put jumper between brown/gray wire pin 1 on the connector 2 of the PSE harness and car body.
Mike

Tthanks again for all your help.
OK, I got the rebuild pump back and it seems to work well.
Central lock and lumbar seat control works perfect and the trunk handle comes in and out. The car runs again...
BUT the trunk still only closes when I slam it hard. The trunk close assist feature does not seem to work.
Which pump handles that? All my doors work perfect.
When I close the trunk lock manually (to trick the trunk to think it's closed), the handle retracts and the latch on the lid pulls back just about 2mm and then releases that same amount again.
Isn't that latch supposed to come out quite a bit to slowly pull the trunk lid down?
How can I troubleshoot this last issue?
regards,
Sab.

__________________
regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged