If you are using our remote rollover vent valve # VVR make sure that the vent is mounted vertically. Mounting the vent at an angle may cause the vent to shut off.I didn't see this before. If you are using our in-line remote rollover vent valve # VVR-IL make sure that the vent is mounted vertically with the check ball in the bottom fitting. Mounting the vent at an angle may cause the vent to shut off