I'm sorry you are still having problems with this. I found that when I tried to reinstall the pump/primer assembly as per the repair instructions, I had problems pinching the o-ring. So what I did after dis-assembling the unit, I removed the integral output tube from the pump head by sliding it up & out of the pump head (see photo)
This allowed me to install the new o-ring on the pump/primer assy., lube it well and then re-install it from the top of the filter housing rather than from the bottom as called for in the repair instructions. Just push it in far enough so that the integral output tube lines up properly before you snap it back into the assy.
There is a small lip or ridge in the housing that can cause the o-ring to be pinched. It was much easier to re-assemble without pinching if you did it my way.
Also, the 'old' Eheim lube you have should be perfectly fine to use. I just used a lot of it to make sure the o-ring was greased up well. BTW, make sure the o-ring isn't twisted when you install it in the pump/primer assy. groove. It has a preformed shape that should be maintained when you install it in the groove. Make sure it is installed in the groove closest to the integral output tube. In other words, the groove that is the farthest away from the motor and electrical cord.
Hope this helps. Keep us posted on what you find out.

This allowed me to install the new o-ring on the pump/primer assy., lube it well and then re-install it from the top of the filter housing rather than from the bottom as called for in the repair instructions. Just push it in far enough so that the integral output tube lines up properly before you snap it back into the assy.
There is a small lip or ridge in the housing that can cause the o-ring to be pinched. It was much easier to re-assemble without pinching if you did it my way.
Also, the 'old' Eheim lube you have should be perfectly fine to use. I just used a lot of it to make sure the o-ring was greased up well. BTW, make sure the o-ring isn't twisted when you install it in the pump/primer assy. groove. It has a preformed shape that should be maintained when you install it in the groove. Make sure it is installed in the groove closest to the integral output tube. In other words, the groove that is the farthest away from the motor and electrical cord.

Hope this helps. Keep us posted on what you find out.