Proper tire pressure is important for maximizing ride efficiency and avoiding flats. A great bike pump with a built-in pressure gauge can make checking and topping off your tires before a ride quick and easy. However, if you've ever had an ornery pump, you know there are a few problems that a faulty pump can present.
The most common problems with bike pumps involve faulty seals. Over time, the internal pressure created in a pump can cause leaks where the hose connects to the base or the head. When this happens, air leaks out with every pump, making it extremely difficult to fill tires. Another issue is a poor seal around the head. The small rubber ring within the head can wear out, creating leaks and preventing an airtight seal between the head and tire stem. The result is often a head that pops off of the stem once pressure is applied. Finally, a faulty gauge can create problems. Recommended tire pressure will vary by wheel and tire type, but it's important to have the right pressure, especially if you're going for speed.
What to Do
If you have a problematic pump, it may be time to replace it. It's often easier and more cost effective to buy a new one than it is to repair a broken pump. The exception to this is rebuilding the head. This is easy for most people to do on their own and repair kits only costs a few dollars.