Sam, I believe you are right on the money in general. Instead of buying a cheaper inductive timing light perhaps borrowing one might be an option for a test? Or even purchasing a cheap one from a retailer with a good return policy and returning it in the condition recieved if it works no better? A lot of earlier ones are around and no longer used much as they do not usually incorporate the dial in timing feature. The problem you are experiencing could be from the output of the pizzo amplifier. There is a slight possibility that a ringing effect or the injector line turn on and turn off pulse might be confusing the timing light amplifier in some fashion for example. The trigger point 180 degree out is quite interesting to consider the cause of for example. I could easily understand the 10-20 degree discrepancy causitive factor you experienced earlier but about 180 degrees out leaves me wondering. Also a unit far cheaper than 60.00 timing light may be benificial. How about contacting the pizzo amplifier builder to find out if they recommend any particular unit that seems more compatable with their unit in general. Also some consideration of what is most likely happening here might be useful from our electronic friend. It might also be worthwhile try to power the timing light and perhaps the pizzo amplifier from an isolated battery. Or start the car and remove both battery terminals from the battery to allow yourself a known clean voltage supply for both amps. That is just to eliminate the possibility of something other than the pizzo amps output getting into the timing lights amplifier or pizzo amp as well from the power supply. Like random or steady pulses from the alternator. For the sake of argument call it electrical noise. Unlikely perhaps but something is affecting something. The snap on timing light amplifier has to be false triggering or confused by something. I have seen indications of and our friend has looked at things with his scope floating around on our old mercedes electrical systems. They do not impact the function of the car but if getting into either amplifier through the power supply they just might upset the apple cart somewhat. You have worked far too hard to not bring this pizzo aproach to a reliable and succesful conclusion.

Yes Michael I totally agree. It will always be required to check the plugs calabration with each other basically by interchange. Thats if you are doing all the cylinders at once. Making any individual plug the standard refference is probably the simplest and certainly the most accurate approach. You just then move it around as you suggested. This you do as soon as you find unusual differences in your initial voltage readings before anything else. When checking injectors for instance move all injectors one by one to one known cylinder for comparison of voltage readings. It is a solid check of them. We are looking at dynamic testing here overall. Also we want a high degree of consistant accuracy. You expressed it well. These pretty simple preliminary steps being bypassed will lead to the most serious errors in the long haul in my opinion with the milli volt approach.

about the rotation of a single Glow Plug from cylinder-to-cylinder... and then the rotation of each of the injectors to the same cylinder. This really grabs the logical side of my brain [whichever that is]! I think this is my next Saturday project with my 240D... in an effort to diagnose why it runs as rough as it does. By the way Barry, what are the odds that the roughness is bad motor mounts?

New Subject – Barry, just today we tried your ideas about using a separate battery to power the “Tach-N-Time” meter and timing light. We used the same hi-tech fancy Snap-On light so I’m back to my last impulse which is to buy a new inductive triggered timing light… again a very basic one that does havfe a brighter “Xenon” type of flash bulb. Harbor Freight has one for less than $15 but at that price it might be a complete waste... plus they were out of stock anyway! I think the $40 to $60 models at Kragen is probably the route I will go for they even carry spare parts/accessories for those models!

Regards,
Sam