It has happened to me once it was the mass cable of the battery that did not make contact in chassis, check the cable well and the route sometimes sulfates or loosen up, then that valve if you are going to disassemble it attention to the pin can fall, check if it comes out with aluminum remains that if so it is the pump that is defective and is losing metal, but I do not know that amount of km you have traveled but first of all, you have traveled but first I said, if you have an auxiliary cable you can put it from the battery to the engine and tests, be sure that it does the contact and Puebas if everything goes ok Eureka, if you do not try to turn off the car and if you do not turn off you use the ground cable as I said tests first directly to the engine and if you do not turn off you connect it to the body, remember the negative cable of the battery. greetings