240D Central Locking vexation
 

Since my car is out of commission while I await the funds to procure a new Diff and start a rear end re-build I figured I'd tackle the central locking system which the previous owner told me had been disconnected because they "didn't want to mess with it"...

Can anyone tell me how the three way valve in the drivers door is supposed to function? I cannot get it to pull any vacuum with the mityvac attached to the first connection with the rod in either position.

With the vac on the last connection there is a medium speed leak with the rod all the way closed and it holds no vacuum with the rod open. I'm guessing this is faulty but I'd like confirmation before I shell out the money for a replacement.

Also. Does anybody know how the fuel door module and the trunk lock module are supposed to work?

- Peter.

Vacuum is supplied to the central port of the master switch (by the yellow line).

To test the switch:

Sit in the driver's seat and close the door.
Plug the first (aft or left) unlocking port (yellow and green line), and the plug third (fore or right) locking port (yellow and red line).
Apply vacuum to the central port with the door unlocked.
Then, apply vacuum to the central port with the door locked.

If it holds vacuum in both positions (locked and unlocked) the master switch is okay.

Are you sure the yellow green and yellow red lines are meant to be attached in the positions you describe? Because on mine they were attached the opposite way round. I mapped out the entire system so I could see if I could identify how the PO had messed with stuff.

- Peter.

Pretty sure its is that way...that is how it is setup on my W116s.

With driver's door locked (shaft of actuator rod in master switch is retracted) and vacuum applied to center port, then vacuum is mantained when the third port is plugged.

The central locking system can act strangely depending on the areas that are leaking.
Attached is a link to FSM job 80-260 Checking central interlock.
https://www.startekinfo.com/StarTek/outside/12265/program/Chassis/80-260.pdf
I'm going though this very process of sorting out the central locking system with 'Stormcloud' at present.

Keep at it and you'll get it working properly.:)

Thanks for the PDF. I'll see if it can add anything to the process. So far I've checked literally every single vacuum line individually and found no leaks. I've also confirmed no leak in the trunk resivoir. And no leaks in the other three door actuators. So as I see it that leaves only the drivers door valve and the fuel filler cap and trunk lock as possible culprits.

- Peter.

What is the symptoms of your problem before YOU started messing with it? Does it lock and unlock like it should when you apply vac to it as the switch would?

I have a few diffs if you need one...

That's the thing. I have no idea what the original symptoms were as it was like that when I bought the car. The PO had done "something" to the system so that the drivers door lock operated on it's own and the other doors remained locked all the time. As I had no idea what the PO had done I figured I'd start by mapping out the exact path of the cars vacuum lines so I could compare them with how it's supposed to be to see if anything had been changed or put back backwards etc. Also test every line and component at every stage for leaks and functionality.

I have a nice color coded diagram of the entire cars vacuum system now so I'm trying find out if the lines are actually connected to the devices in the correct manner.

When I say the drivers door operates on it's own. I mean that it locks and unlocks with the key, but the rest of the doors remain locked at all times. The fuel flap does not lock at all and the trunk lid is permanently locked. Requiring the key to unlock it at the latch.

- Peter.

The driver door is the only one that does not operate in vacuum. So, if there is zero vacacuum you can still get in the car at the driver door. Nothing would have to be done to arrive at that condition. Driver door working and everything else not working would be a natural fail condition.

Basically, one pipe to the three way is constant vacuum from the pump or tank
The switch in one position “sucks” to unblock
Switch in the other position sucks to lock
If there’s no vacuum coming to the switch then it’s somethig between the switch and under the hood
You should be able to lock and unlock with a hand pump depending on what side you suck. I think your on the color codes already. Y/G unlock Y/R lock

If it is not operation and or not holding vacuum on either then there is a leak.

I get that. I just want to be sure that the red and green lines are connected in the correct positions.

There is vacuum from the pump to the switch on the yellow line. The vacuum pump was rebuilt a few years ago and a new main line installed from said pump to the brake booster. I've tested vaccum from the pump, it's good. And tested on both ends of the yellow line from under the hood to the other end in the door. It's good. Holds 25Hg's on the Mityvac. But when you attach the line direct to the switch and block off the ports on either side of it and pump from the beginning of the yellow line under the hood then you get a slow leak. About 1 HG every 7 seconds.

I am unable to get the rod to move by pumping irrespective of what position it is in no matter which port I'm pumping on with the Mityvac. Even when it builds pressure and that pressure is released if I manually move the rod (as if I were turning the key).

- Peter.

The center port on the driver door valve is the source. Attach your mityvac there.

Disconnect the two outer hoses at the joints below the valves. Plug up both these joints with golf tees.

Set the drivers door to the locked mode (lock knob pushed down) and pump up the mityvac. Pull out the golf tees one at a time from the outer lines. If nothing happens the line you just uncapped is the unlocking line. If the line whooshes and the vacuum is lost that is your locking line (red-yellow goes here).

Now plug both lines up again, switch to unlock mode, pump it up again, now the other line should release the vacuum and the other should hold. The one that releases the vacuum is the unlocking line (green-yellow goes here).

Also try just pumping it up and leaving both tees in place, then switch modes back and forth and leave it for a couple minutes in each mode. The switch should maintain vacuum.

If you can’t hold vacuum in the switch, or the behavior of the ports is not consistent, the vacuum switch is bad.

You should also be able to pull vacuum on the red-yellow line and lock all the other doors. then pull vacuum on the green-yellow line and everything should unlock.

The early models (including 123/1st gen 126) use a two-pod system, the red-yellow line pulls all the pods to lock and the green-yellow line pulls to unlock. Note the fuel door has a single lock pod, there is a spring to pull it back to unlock after vacuum is removed from the lock line. Once a pod pair (except for the fuel door) is pulled to one position or the other, it is stable in that position even if vacuum is lost on that side. It requires releasing the vacuum on the one side and applying it to the other to get it to change modes.

Contrast with the 124/later 126/210 system where these use a single pod and an electronic pump that either sucks (unlock) or pressurizes (lock).

Some excellent specific steps here and I shall follow them. Thank you. One thing I can state already though is that my fuel flap mechanism appears to be incorrect. The device I have at that location has two vacuum ports, one of which has the yellow red line attached and the other the yellow green. Possibly this has been replaced with an incorrect part at some stage in the past. It looks similar to the actuator that is on the trunk latch.

- Peter.

This is the case. Whatever else may be wrong with the system I am now certain I have a bad drivers door switch. So I'll be ordering a new one.

Doesn't work. Don't understand this I have verified the integrity of each section of vacuum hard line in the entire system. I did this by disconnecting each rubber distributor and capping off the far end of each section and pulling vacuum with the Mity vac at the opposite end. I have no leaks in any length of vacuum line. Additionally all three door actuators lock and unlock when I connect the vac directly to the respective ports on the devices themselves. So if there are leaks they have to be in three way and two way rubber connectors under the carpets and in the trunk. I guess I'll go ahead an order new ones of these as well.

The only other places in the system that could be causing problems that I can figure would be either the fuel flap or the trunk lock mechanisms. I think the fuel flap mechanism may be incorrect. I might try bypassing that altogether and see if I have any luck.

- Peter.

Yep those rubber joints go bad after 40 years and leak. The hoses can also crack inside the door boots where it flexes.

If you follow the WIS instructions in post 4 it will take you through step by step. They show a proprietary MB vacuum tool but a mityvac will work just fine for this.
Note if you are trying to follow that link on a mobile device it will try to take you to m.startek.info instead of the original site. Depending on which browser you use there is an option to force it to load as a desktop site, then it will work.

You can still order vacuum line from the dealer in color code but it is $$$
Pelican sells generic translucent tubing. Just use a sharpie to color code at each end.

Sampson Autoparts South Central L.A.
 

5.22

So ;

Where are you at now ? .