Guess my previous post was too verbose. Verbose ist verboten, ya?
Problem: trunk latch won't disengage with the key turned to ANY position. Cylinder has just been rekeyed and lubricated but when I install it, the lock 'button' doesn't go all the way in. Maybe the locksmith reassembled it wrong. Possibly the problem is with the upstream vacuum since the car's gas-fill actuator doesn't work. It seems to me that the lock should open with the key regardless of upstream vacuum but I don't have a schematic of the '83 300CD system. The 2 door locks open & close properly with the key....
Any idea if this is a problem with how I'm installing the lock?
Or is this a vacuum problem?
Is the problem really not going away until the gas latch issue is resolved?
Many thanks,
Chris Collins

The lock should function properly regardless of the state of the vaccum system. It is possible that if the actuator is jammed in precisesly the wrong position that it might interfere with the the function of the lock but I doubt it. I'm assuming since your installing the tumbler that you have the trunk open.. if so just disconnect the actuator from the lock. Since you've stated the vaccum system is toast anyway.

__________________
'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.

With the drivers dorr locked, the trunk will not open regardless of the keyed position. So yes, the vaccum system can affect the trunk lock.

On my '84 300CD, my '84 300D and my wifes '83 300D, regardless of the door lock positions, the key will open the trunk lock.

You have to turn the key to the left into the horizontal position, then turn it a quarter turn further and press the button while holding the key in position. You can feel the latch engage.

When I first bought the '84 300D it wouldn't open at all without the key. But that was becuase the PO's mechanic (who had just fixed the trunk lock) put the vacuum actuator on incorrectly.

__________________
'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.

Do you have any alarm problems. There is a cable under the rear seat (and insulation pad) that should release the lock on the trunk.

__________________
84 300D 251K
87 190DT 281K - Sold
06 Ford Escape 172K
94 Ford Ranger 250K
99 Chevy Suburban 181K

left position, with BUTTON PUSHED IN.

I decided to go the low-tech route of disconnecting the vacuum at the trunklock actuator. This gives the button a very flacid feeling but allows it to lock without any trouble. Thanks for the posts folks!