I just had the strong engine transplanted from my worn out 123 300D (77) chassis to a fine '80 123 chassis by a local shop with a good reputation. The mechanic is a capable chap but has limited diesel experience. He wants me to take the car to someone with more MB/diesel experience to correct the leaky injectors that are apparently the result of months of sitting waiting for another body to come along.
One or two injectors seeped a little when I parked it and the guy says that once it starts, it will run all year. However, if it sits for any length of time, (over night) it will take a can of ether (sans glo) to prompt it to start again. I meant to ask him if he knew about the little pump on the injector head that bailed my ass out the time I ran the car out of fuel some years ago. It may not make any difference. I know little about any of this.
The engine was rebuilt several years ago and the MB specialists told me that the engine was in over all good shape before I had them swapped. Good compression and all that sort of thing. I had to keep the '80's vacuum assisted tranny due to some physical mismatch and the fellow had to swap glow networks for some similar reason. That didn't seem to phase him in the least but he doesn't want to deal with these injectors. My Saabs would have leaky injectors from time to time and even I fixed one or two of them. I gather there is some major difference (aside from fuel type)since I am the Moe Howard of motor repair.
The mechanic also can not get the engine to shut off with the ignition switch. He is aware that it is a vacuum control of some type but is stumped as to why it won't shut off. He reported that someone had cut the wires to the switch at some point prior but he reconnected them. The rest of the wiring is seemingly fine. I assume these are starter wires. When I got the first 300 all those years ago, I was warned by other enthusiastic owners that some day, the car will simply refuse to shut off and the top mounted "stop" lever will be required. It never happened to me but one day it "ran on" or "dieseled" but shut off after a few seconds. I would appreciate any input from this informed forum about these problems. Cheers!

Two things. I would replace the fuel filters and make sure that they are tight. Any air here and the car won't start.

The vacuum system IS what turns off the engine. To test, just connect a vacuum pump to the shut off element and pull a vacuum with the engine running. It should stop. If so, you have a source problem.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS