Hi all, first post from a long time forum viewer!

I have a '93 MC21 SE that I have been restoring over the last year or two. All was going well till I found a puddle of oil leaking from the left side of the engine. It's been really hard to track down the source of the leak. After much reading and searching it became clear that I may have a dodgy crank seal. It was also pretty clear that I needed to check the condition of the center seal. I purchased a leak down test kit and yesterday spent some time removing the carbs & expansion chambers. I have blocked off both exhaust ports and the carb manifold on both sides. The boost bottle is still in place so no leakage there.

The problem is that I cannot get any pressure at all into either cylinder. Not even a flicker of the pressure gauge. Another post on this forum mentions that I'll need to block the crank "oil feed port" otherwise there will be no proper seal for the test.

Can anyone tell me how I do this? Do I need to remove the oil pump and block off the port there? Is there something else that I'm missing? The engine actually runs OK so I am assuming that the crank seals are still in half reasonable condition (if both have failed then that might explain no pressure!).

Any help would be appreciated.