I've understood my problem. It was not du to ejb-jar.xml in war. This is right. It's du to CDI that is not enabled for both ejbModule and webModule. Here are some explanations : https://issues.jboss.org/browse/WELD-778
so I just put my ejbModule in my webModule like this :
-- lib/other.jar
-- monwar.war (with WEB-INF/ejb-jar.xml)
-- WEB-INF/lib/mesejbs.jar (with META-INF/ejb-jar.xml)