First of all you should try to run the TOMCAT using it's own .bat and not the Eclipse. If it doesn't run then problems would be on the tomcat installation and not in a Eclipse and you could take the look to the files of TOMCAT_HOME/logs/ where Tomcat's errors are always traced (they are very helpful).
Anyway, if it runs properly out of a eclipse, try to delete a eclipse's tomcat configuration and set it from a beginning following these simple steps
· Go to a Eclipse's Window > Preferences > Server > Runtime Environment and add the Tomcat Server browsing the TOMCAT_HOME and selecting a suitable JRE (use JAVA_HOME that contains the jre yet) paying attention to the messages requiring a certain JDK depending on a TOMCAT version (TOMCAT_8 requires at least a JDK_1.7 version and, if not set, usually shows the errors explaining it when starting)
· Go to a Eclipse's Window > Show View > Other... > Server > Servers and add the new server; in this case a version of TOMCAT you set before. You don't need to add the further configuration to make a TOMCAT to start.
· At this point if would be the helpful if you hadn't had any app at TOMCAT_HOME's webapps folder but those that came default then(you must empty a TOMCAT_HOME/work folder to remove a cached stuff). Once you have ensured it, then start from ECLIPSE and cross your fingers. In case of fail, take the look to Eclipse's console and look for a exception to copy at this post