W123 won't go anywhere...sometimes
 

Hi all, so I have strange problem that I'm hoping someone might be able to help with. I have an 83 300DT that I recently took to a mechanic to have the ignition lock replaced because I couldn't turn the key anymore. When I got the car back, the door locks didn't work anymore, the engine wouldn't shut off after I removed the key (this happened intermittently) and occasionally the car doesn't have ANY power at all. When in gear, I can put the pedal to the floor but the car is extremely sluggish and barely moves at all. Sometimes it will move a bit but it's extremely slow going and then the turbo kicks in and it slams forward kinda hard. (the engine doesn't even rev up when in gear...however, when it's in park it does rev up.) To remedy this I just turn the car off and restart it and after a couple attempted starts it finally starts normal and then drives normal. This all sounds like a vacuum issue to me but when I took it back to the mechanic he said it was unrelated to what he worked on... Does this sound like anything obvious to anyone? Thanks for ANY info you might have... Dan

Definitely a vacuum issue. You mechanic most likely buggered up something with the vacuum system when he changed whatever he changed. Question: Did he just change the tumbler assembly, or did he change the whole switch?

Sounds like the vacuum shutoff on the injection pump may have issues working properly. When the mechanic changed the switch there is a vacuum control device on the rear of it.

The mechanic may have impacted this in some way so keep an open mind. If the fault started right away after the switch was changed my money might be on that area. If not an issue right away may just be coincidence.

He may have even pulled the vacuum line through the firewall and buggered up the rats nest of vacuum lines above the oil filter....

Sometimes the vacuum in the engine shut of system doesn't evacuate fast enough when you turn the the key to start the car.
Specially when the engine is hot and you don't have to pre glow.

Turn the ignition on and wait a few seconds, then start the engine.

Did you by any chance have an oil change done on the same visit to the mechanic? Just wondering. It is very easy to disturb the vacuum lines, and pull one or more loose, when doing the filter. (Or as Cooljay pointed out, he may have done the same thing by pulling the vacuum line through the firewall... though he shouldn't have been in contact with that if it was just the keyswitch you had done.)

For the door locks and shutoff, it does sound as though there are issues with the vacuum lines under the hood. It could be as little as vacuum line pulled out of a rubber joint. Look for a stray line open to the atmosphere.

As for the lack of power, I don't understand how a vacuum leak would cause that. Some suggestions:

First thing to check, if you have floor mats, is that the mechanic didn't move the driver's mat and bunch it up behind the accelerator pedal (or even drop some debris that is stuck in there).

Second, check that the pressure sensing line (plastic tubing, either clear or could be very yellow from age) running into the ALDA (mushroom shaped device on the top of the injection pump) is intact -- not only connected, but not split/broken.

Third, with the motor OFF, try moving the throttle linkage to see if it moves without binding.

Skippy: The mechanic changed the whole switch (lock), but installed my original tumbler (or cylinder).

I checked all the vac lines in the engine compartment and they are all intact. I disconnected the door lock vacuum line from the 4 way rubber connector and that seems to have taken care of the engine not shutting off when I remove the key, but obviously the doors locks are still broken and the loss of power is still an issue. The mats are not an issue, they are where they are supposed to be with nothing blocking the pedal...The throttle linkage checks out fine.
I'll have to go check the pressure sensing line to see if that's ok or not...

It is possible to put the switch vacuum lines on wrong. Since your clarification of what he changed there is a chance that has happened. Easy initial test is to remove the vacuume line from the shutoff and block it. Does car now run normally? Other than not shut off of course with the line disconnected.

Zacharias: I was thinking the lack of power could possibly be related to vacuum due to the transmission being regulated by vacuum. When the car starts funny and is sluggish it feels kind of like I'm trying to move from a stop in fourth gear or something... I don't know, it's just a guess on my part, I don't know much about these transmissions...

Barry, do you mean the vacuum line from the back of the ignition lock assembly (don't know the exact terminology sorry)?

The vacuum would not make the car start in a higher gear from rest... the vacuum sends a signal to a modulator that controls shift timing and comfort by acting on internal pressure. If the transmission IS doing that, trying to start in a higher gear, it would be a major internal issue and completely unrelated to vacuum or what the mechanic did.

There are linkage issues that can cause the sluggish behaviour you describe, but they would be constant, not come and go.

I was too hasty in declaring your performance problems as not vacuum-related. Now that you have the shutoff working, try taking the car for a drive.

He switched the vacuum lines on the shut off portion of the ignition switch. Swap them around and I'll bet you'll be good to go.

X2

There are vacuum connections to the switch that can be put back on wrong. Doing the easy test I mentioned would determine if the issue is probably there. Although it sounds like you have other issues as well. If the lines to the switch are installed wrong I believe the vacuum for the engines shut off valve on the injection pump is not released properly.