Maintenance method Disassemble the injector, grind the cone surface with a little chromium oxide fine grinding paste on the head of the needle valve (be careful not to stick in the needle valve hole), and then wash it with diesel oil and put it into the injector for test. If not, replace the needle valve pair. If you still have questions about this, you can contact us, we will provide you with professional answers and products. https://wdpart.com/collections/fuel-injector-nozzle