The loosely coiled metal spring in the ink chamber of some converters is not a defect but a deliberately fitted agitator. Its job is to keep ink reaching the feed. In standard converters without it, once a smaller quantity has been used up the ink can cling to the rear of the chamber; at the front nothing but air is then drawn into the feed and the flow dies. Because the spring follows every movement of the pen, it prevents the ink from settling in this way, and tiresome shaking becomes unnecessary.
Many disposable cartridges use the same principle, though there with a small ball. In a converter a ball would be useless, because it would cover the opening to the feed and so hinder the pressure equalisation needed when the piston is worked. An open coil spring, by contrast, lets ink and air pass forward unhindered. Finding such a spring loose in a converter is therefore the normal state of affairs; it should not be removed.