Both of my locker pumps are doing the same thing. They work and will lock the axle but appear to have internal leaks. When activated they pump up like usual and look the axle then cycle off/on intermittently quickly. I believe this is the internal pressure switch reactivating them to keep the pressure then shutting off quickly when reaching 5 psi. When removed from the vehicle, powered by 12 volt source, and with my finger plugging the output hose, they do the same thing so I really think the leaks are internal to the pumps. I've seen posts about replacing the pumps and the fact that new ones are not available and I am aware there are other proven means to activate the lockers but I would like to continue using the factory pumps.