some info (kinda long!)
I just went through vacuum troubleshooting hell not too long ago on my uncle's '78 300D. His had numerous bugs - the engine had a delayed shut-off, the door locks didn't work (the trunk and gas lid would lock...but the trunk wouldn't unlock), the climate control would not turn on in Auto mode, and the brake booster didn't seem to provide the 'boost' that it should.
Funny thing - the trunk lock had a massive leak on the 'unlock' side (yellow w/ green stripe), but would hold vacuum on the 'lock' side (yellow w/ red stripe). This alone caused the door lock system not to function, the lack of brake boost, AND the climate control to act up. Once I replaced the trunk lock, I found that the brake booster now had more 'boost', and the door locks worked- but very very slowly, and the engine shut-off delay wasn't quite as bad. After some more testing, I found that the right-rear door had a leak on both lock and unlock circuits. You can access the lines going to the individual doors underneath the carpet in the passenger side footwells (yellow/red = lock, yellow/green = unlock). Once I got the door lock actuator replaced, the locks would lock/unlock much much faster! Unfortunately the delayed engine shut-off was still there AND the door locks would only function 1-2 times after the engine was turned off. I checked the vacuum resevoir in the trunk by pulling the yellow w/ purple stripe vacuum line in the engine compartment and pumping it down w/ the mity vac - after a bunch of pumping, it held vacuum just fine. (The other smaller vacuum components should hold vacuum after just a handful of pumps.) From there I checked the shut-off valve on the injection pump (brown vacuum line going to this) and the shut off valve had a slow vacuum leak! I replaced this and now the engine shuts off immediately w/ the key and the door locks function as per the factory specs of 10-12 times after the engine has been shut off.
I'm sorry I had to make such a long post but I thought that maybe it would help you get an idea by telling you what I did to fix my uncle's car. You might be lucky and find one single faulty component causing all the problems you're having w/ your car...or you could have a situation like I did with numerous leaks causing many problems. If you need any more help or anything please don't hesitate to ask! Good luck!
I just went through vacuum troubleshooting hell not too long ago on my uncle's '78 300D. His had numerous bugs - the engine had a delayed shut-off, the door locks didn't work (the trunk and gas lid would lock...but the trunk wouldn't unlock), the climate control would not turn on in Auto mode, and the brake booster didn't seem to provide the 'boost' that it should.
Funny thing - the trunk lock had a massive leak on the 'unlock' side (yellow w/ green stripe), but would hold vacuum on the 'lock' side (yellow w/ red stripe). This alone caused the door lock system not to function, the lack of brake boost, AND the climate control to act up. Once I replaced the trunk lock, I found that the brake booster now had more 'boost', and the door locks worked- but very very slowly, and the engine shut-off delay wasn't quite as bad. After some more testing, I found that the right-rear door had a leak on both lock and unlock circuits. You can access the lines going to the individual doors underneath the carpet in the passenger side footwells (yellow/red = lock, yellow/green = unlock). Once I got the door lock actuator replaced, the locks would lock/unlock much much faster! Unfortunately the delayed engine shut-off was still there AND the door locks would only function 1-2 times after the engine was turned off. I checked the vacuum resevoir in the trunk by pulling the yellow w/ purple stripe vacuum line in the engine compartment and pumping it down w/ the mity vac - after a bunch of pumping, it held vacuum just fine. (The other smaller vacuum components should hold vacuum after just a handful of pumps.) From there I checked the shut-off valve on the injection pump (brown vacuum line going to this) and the shut off valve had a slow vacuum leak! I replaced this and now the engine shuts off immediately w/ the key and the door locks function as per the factory specs of 10-12 times after the engine has been shut off.
I'm sorry I had to make such a long post but I thought that maybe it would help you get an idea by telling you what I did to fix my uncle's car. You might be lucky and find one single faulty component causing all the problems you're having w/ your car...or you could have a situation like I did with numerous leaks causing many problems. If you need any more help or anything please don't hesitate to ask! Good luck!
