I bought a piezo guitar microphone, clamped it on the #1 inector hardline of my 85 300D and took the pic below on my oscilloscope. There is a lot of noise (which is to be expected) but you can see the 2 disctinct pulses which are 40 milli sec apart (25 hz). The engine RPM is probably somewhere around 650 to 700.

Is this signal plausible? I don't know the relationship of RPM vs injector pump firing rates on a 5 cylinder 617.952. I don't want to waste my time trying to amplify and filter this signal if it is garbage.

This is my first step in attempting to come up with a timing light triggered by injector line pulses. Wish me luck.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked