1991 Plymouth Voyager Starting issues

I turn the key and can hear the fuel pump. The engine turns like it wants to start but no ignition. I do this usually about 3 times or so and then it will start. Sometimes after the engine has run for a while it will start right up if it hasn't been off for too long. Usualy when the engine has been off or is cold it will take 3 to 4 times before it starts. Any suggestions on what I can do to fix this problem would be greatly appreciated.