We're currently involved with a piezoelectric injector system on a Landrover TDV6 and I came across this brilliant example of a forced voltage test to measure the actual travel executed by the piezo stack at different voltages. If I had an up to date scope and an insulation tester mentioned in the video I would be tempted to do this test in conjunction with an oscilliscope as a really informative case study on piezoelectric injectors.
Seeing is believing!
What I also found interesting in this video is that the stack did not "shrink" when the lower voltages were applied. Only when 100v plus was applied did it shrink back.
Based on the readings I took on Friday on our problem child engine, I suspect we started off with very low current readings on our injector, backed up by the fact I only saw a positive spike on the waveform and not the reverse spike?
Unfortunately I'm at home at the moment (I know it's Sunday but I'm losing sleep over this job), but I will carry on my diagnostics on this vehicle and hopefully post up a really good case study on the problems we are encountering.