Review on Efficient Inline Spark Plug Tester: Engine Ignition Diagnostic Detector for Automotive Car Lawnmower Internal External Engine (1) by Timothy Bobbert

I needed this product urgently due to an ignition problem with a 22hp twin engine lawnmower. After getting them, I tried using them to diagnose an intermittent weak spark problem. Only one worked and the other had no spark at all, which was impossible. When switching the good spark tester to another cylinder, it showed a constant spark. After swapping the LED between them, it turned out that the LED lamp was defective. I then switched to my old Auto Zone adjustable spark gap tester, which proved to be more reliable. The negative reviews about the "lack of quality control at the Chinese factory" turned out to be true. Returned to Revain today for a full refund.