Thought I’d bump this thread. While chasing down my SD’s vibration issue I thought I’d check timing. I noticed the Sealy piezo to xenon timing light converter box was on amazon for $150 including shipping to California. So I bought it. It had very mixed reviews and I decided it was worth a try.

I have a background in ultrasonic sensing and electronic instrument design. I was tempted to try to roll my own with some piezo elements I had around a long with some amplifiers and Schmidt triggers. But I’m burned out after a career designing these exact systems so I just threw $150 at Amazon and rolled the dice. I didn’t read all of funolas posts on this and I kind of quit when I realized I would have to design a trigger loop for my inductive timing light pickup which means a high voltage wire replicating a spark plug wire. Outside my expertise.

Anyhow the Sealy came and I give it mixed reviews. It did work. But not consistently. I can clearly see my timing light strobing and indicating 19 BTDC. But it is really a twitchy measurement.

Depends a lot on how firmly you put the probe on line 1. Too tight it picks up every sound the engine makes and it blinks the timing light at the wrong times and too often. Too loose and there is no signal. You have to twiddle it till you get a clean signal. Once you get in the neighborhood of main peak for injection 1 you’ll see your timing mark kind of come out of the fog as the light triggers more often at the correct time. There is scatter, noise and the mark wanders as you play with the cables.

What I haven’t figured out is if I move the light at different angles I can change the timing a bit. Now that is straight out odd. So the device leaves some doubt. So it works but it is very fiddly.

I opened it up. There is a cheap amplifier followed by a little 8 bit microprocessor. The amp looks (I’m guessing I’m too lazy to reverse engineer) like it amplifies, offsets and maybe thresholds the signal. There is a pot that looks like a offset adjustment.

I’m not sure what the microprocessor is for. It blinks the light. It accepts the input from the amps. I’m not sure if it is sampling and converting the signal...maybe that and then thresholding digitally to pick off the biggest pulse. I say maybe because it triggers too easily on noise to be doing anything “intelligent” with the signal.

The signal funola shows could benefit from some AM detection. Not sure whether Sealy does this or do they just amplify and window threshold which is the easiest way.

Anyhow the microprocessor blinks the light and runs a current through the inductive pickup loop to trigger the timing light in response to the rising pulse.

Basic but it does work. Kind of a university student level design.

Do I recommend it? Well...I guess at $150 it is ok. I did get an answer. It isn’t snapon diagnostics quality by a long shot. I’ll attach some photos.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

Unit


Board, basically two integrated circuits. One amplifies and possibly thresholds. The white plastic screw pot is probably an offset from what I can tell. Then the signal goes into the big chip which a microprocessor running at a few MHz. It is either sampled and processed digitally or just thresholded and converted to an output pulse to drive the light and the inductive pickup circuit.

Looks like the pickup circuit is pretty simple. I thought you needed high voltage like a spark plug line to trigger the clip on timing light but maybe just a little current will do. There is nothing remarkable here, just a switch as far as I can tell that turns the juice through the loop on and off. Funolas idea to use a bright LED as a strobe is good. No special circuitry there and you don't need an antique timing light. I literally had to go into my dad's garage and dig for our old Sears Craftsman Deluxe timing light. Useless today as modern gassers are coil over plug. I guess I can use it on my 65 F100 though.

All this is a guess of course because the designer used a 4 layer board and hides his tracing under top and bottom copper planes. I didn't feel energetic enough to dig further. He earned his money today as the system worked ok.


Sensor. Basically a few wafers of piezo ceramic material. Looks like Barium Titanate. Ground is on the injection tube and the other end connects to the screw. Voltage is across the screw and the tube. Looks easy to damage if you tighten it too much. These crystals are very brittle.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

If it did work reliably to me the issue still is that you need to time your Fuel Injection Pump with one of the FSM methods then install the new device and see what it shows. After that you have a base point.

That is not very valuable for a parson owning a single vehicle because once your reset the timing by way one of the FSM methods you have thousands of miles to go before it needs to be done again.

Now if you had multiple vehicles same model you might have something.
In particular there is School Bus Companies that have a lot of Smaller Busses with Ford or GM diesels in them. It might be a handy tool for them.

Another way it could vary is if the Injector Pop Pressure was not exact. It might be better to have a special test injector and sub that in when you time. However, that removes the convince and a lot of diesels subbing in another Injector would be a lot of work.

Just some thoughts.

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84 300D, 82 Volvo 244Gl Diesel