Trimmer will start but not run. If you put a spark tester in the circuit from the coil wire to the spark plug the trimmer runs perfect. It works with a spark tester light or a gap jumper tester. I have seen this work on this trimmer several times. I have worked on these things for over 5 years and never seen this before. Would appreciate any explanation for this and a solution for the problem. Thanks. Bill
plug is bad or wrong grade.
testers place e little more resisance so the voltage that ends up on the plug gap is higher because it had to build up enough to pass the tester first.
An old test for an oil fouled plug on a multi cylinder was to pull the plug lead and hold it 1/2 away from the plug till the engine was firing on all cylinders.
