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Your oil system works on crankcase pressure. There is a fitting on the engine where a hose that goes to the tank is attached, this is a pressure hose that pressurizes the remote tank with the engine running.
The cap and gasket on the remote tank must be tight and not leaking air. Start and run the engine. After a few minutes loosen the remote tank cap, you should hear air escaping. If not then check the hose to the tank while running for pressure.
With a 13 year old engine you also need to check the hoses thenselves that they are not collapsing or blocked.
Try these and post back what your results are.