What weight oil are you using? These can be finicky with anything other than the required oil. I would make sure you eliminate the obvious by making sure you have a good battery charge and connections. Also check the connections to the the sending unit. You can check the pressure with a seperate tester guage if you have one available. You can also test the sending unit. I have not personally seen, but unfortunately have been told, that several of these have had problems with partial blockage of the pickup screen.