hi all, still trying to narrow down what is making this knocking noise. It is in somehow related to the number one cylinder area. I know this, because if you put your fingers on the number one hard line while the engine is running you can feel the a pronounced thump that is in sync with the knocking sound. the other hard lines you can feel it, but not near as much.

What i've done so far:

1. diesel purge, noise completely disappeared until i hooked it back up to the tank.

2. changed all fuel lines and filters.

3.changed and pop tested nozzles to within 40 psi of each other.

4. today i swapped #1 injector with #4 and the noise and pulse feel stayed on the number one hard line.

any ideas? is there any way the injector delivery seals could cause this or something else in or dealing with the injection pump?

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'92 300D 2.5
'99 E300TD

If you measured "start of delivery" by removing the innards of the #1 delivery valve (on the injection pump), perhaps you didn't re-install the parts correctly. In my 84 & 85 300D's there is a thick disk that must be oriented a certain way. I don't know what results if you get it wrong. I am guessing your car is a 1992, in which case a different injection pump, but could be a similar issue.