This is a good heads up.
hyraulic hoses, like on back hoes, and other equipment that develope a leak can cause the same problems. It`s just natural to run your hand along the hose to find the leak, and all of a sudden your hand or one of your fingers swells up with hydraulic fluid.
lots of times the leak is so fine, but under such high pressure it is hard to see.
I`ll take my injectors to the experts and let them do the testing and not worry about building a pop tester. just one thing to hurt myself on

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Charlie ☺