So for any light loading causing engine motion to occur will mean posters will have to examine their engine shocks from now on. Just another item on the list to keep in the back of our minds. In a way it is good you had the problem so we now know that. . At the same time not enjoyable for you perhaps.

Injection pump replacement with your nice even milli volt readings was unlikely to occur. Or at least I would have argued against it. I have come to the conclusion some time ago there has to be real indicators it is required. Sure element to element timing might be off a shade with age. But for the engine to produce effects that are really percievable to us the burn temperature has to be different from cylinder to cylinder.

Hunter of course was right about the engine shocks function. Just strange that knowledge was not really common on this site before.

I liked your creative self fix approach as well. Perhaps an improvement on the original mount design as well. The worn out or broken shock mounts indicate on your car those shocks were functioning and a real requirement. Call it hindsight. No reason others cannot avail themselves of your fix. I do not think you would mind.

Since some 123 engines have them and some apparently do not makes me wonder what they were thinking at the factory. You would think they would all have had them.

There is still a chance you might get even further improvement when you get the fuel flow through the primary filter looking normal. I really believe there is a normal for that at least.

All the reflected pressure waves in the fuel supply system could produce interesting side effects. Mercedes or the pump manufacturer have designed a couple of things into that system that have me wondering.

The second check valve in the lift pump for example. The fuel filters would dampen the reflected waves somewhat from the injection pump I would think. Maybe not much if the fuel filters are clean.

There are a lot of very short duration spike pulses being generated in the base of the injection pump. could they affect the lift pump if the secondary valve in the pump was defective?

I think inertia of the lift pumps piston might stop any action if they get through. On the otherhand perhaps those spikes combined are generating something that might cause some effect.. They also may be completly benign.

Foaming or surging in the primary filter may be an indication the secondary valve in the lift pump is staying open. The effect might also be more prounounced with the low relief valve opening pressure you had. The presure differrential being larger.

The lower the fuel pressure in the base of the injection pump the more the pressure will try to surge back and forth. Since you adjusted the base pressure I expect you should see less or no foaming. The only indication it might still be there to some extent might be an unstable bubble. The actual air going through is another issue that should not be there at idle.

Where is all this going? Hopefully at some point an eureka will occur that will let us add a modification that improves something that the original designers missed in development. Not too high a chance of it but I for one am looking over time for any possibility of it. The system is basically simple yet there are still things to learn about it I believe.

Do you remember the post where the guys wife complained the vibration was so bad it was shaking her mamory glands at idle? There were a lot of requests for pictures. Now we know that if he had just mounted a pair of engine shocks on her anatomy the problem might have ceased.