Do not waste the opportunity to inspect the glow plugs heating up with the injectors out. The tips should get really hot visually. If they do I would not put in a new set. As you would have no ideal on most acquisitions of the time they have been in service. They could have been replaced not that many miles ago for example. Also have a look for possible carbon buildup in the pre chambers. Many of the aquisitions have not seen highway service for years.

Of note was one poster on this thread mentioned that every thing he did seemed to make some difference. I have advocated going through the fuel system at least partially on any new acquisition for years. How extensive depends on your 0-60 times for the version you have.

At a minumim enough to reduce the chances of an issue while away from home. It is usually very cheap to do yourself. All my versions of 123s are on the faster side of most other similar ones I have driven. Especially the 240ds.

I have another bone to examine as well. I expect these engines to light off as soon as they start to turn over. If they do not something is not right. In reasonable temperatures of course. If they will not do this they are going to be harder to start in cold weather if you need that ability.

A road breakdown can be expected to become ever more expensive to deal with. Every year. Many mechanics have no working experience on these engines. Plus there are other factors that can impact the situation. You want to reduce the probability as much as you can yourself. Doing it all cost less than all the components of just one road breakdown. When far from home.

We are also driving cars that a wait for parts of even just a secondary filter or belt can take time. Mind things like your lift pump is bad. To me it is simply preventative maintenance on antique vehicles.

Our 77 N/A 300d even is not too bad for what it is. The 84 300d has passing ability like a gas car. Or at least feels that way to me. It does so well in that area I am almost positive that the whole system must be functioning like new. I call it just making certain that all components of the system are working well. Not a true restoration .Expected Zero to sixty times are well documented in the archives on each version.