going through the big change... Fuel only to wasted spark

[Piledriver]

My best lean idle is ~13.5-13.8:1, but each motor is different..

Setting best lean idle is just like doing it with carbs, only with no inaccessible screws to twist.

[juki48]

been having issues with starting. once it starts it runs great but during cranking my 12-1 cam signal is a mess,

I started messing with the pots

and then it started.

once it starts it runs flawlessly. the signal amplitude seems to drop on the screen as soon as it starts. is there some stetting that is amplifying the signal during cranking? or do I need to further dial in the pots for a better start every time?

[juki48]

I realized last night the amplitude is a function of time, which is why the skipped pulse is twice as tall as the others. duh.

[jhoefer]

Just going by those trigger graphs, I'd say your trigger voltage is set too high. There are numerous missing teeth per rotation in the cranking plots, but when running at a higher rpm, and thus getting a higher output voltage from the VR sensor at each tooth, the graph is clean. Continue reducing your trigger voltage pot and see if you can get it to clean up.

Might also try moving the sensor closer to the trigger wheel to increase the signal strength at low rpm.

[juki48]

this is actually an optical sensor, so the voltage should be relatively consistent. I'm getting pretty frustrated with the 12-1 wheel in the distributor. sometimes it starts and sometimes it doesn't. tonight it would not start period. I've tried turning the pots all the way down, counter clockwise, and then turning up R56 a little at a time. no matter what I do I cannot get a clean signal during cranking. I can't tell if it's an electrical issue or if the cranking rpm is too inconsistent for the low resolution of the 12-1 at cam speed sensor. not sure if I need to make a 24-2 wheel or just get the CB crank trigger setup.

[jhoefer]

What sensor are you using? Do you have a datasheet? How's everything wired? A couple initial possibilities, sensor exposed to outside light, missing or wrong value pullup resistor, or your wheel isn't sized right for the sensor (isn't blocking the light properly). The sensor output should go between ground and the supply voltage (disconnect output from the MS and test), it should work down to 0 rpm basically.

You will see compression effects, but such a sensor shouldn't be missing teeth at low rpm. You may need to increase the hysteresis level, but I'd probably just start over with both settings, it shouldn't need much tweaking due the the clean signal the sensor should be putting out. Do you have any of the TS filtering settings turned on?

[juki48]

welll.... I had a crane cams optical trigger but I blew it up so I put new LED's in it. this is the thread where I started but I feel bad filling other peoples forums with my stuff... http://www.shoptalkforums.com/viewtopic ... &start=210 I can borrow an oscilloscope this weekend to see what is going on. I find it odd that it runs sooooooo good once it starts.

[jhoefer]

You don't need a voltage divider on the LED, so drop the 510 resistor. Look up the LED's normal continuous forward current (If) on it's datasheet, find the voltage that corresponds to that (Vf) in the graph or table, subtract that voltage from 5V (Vcc). (Vcc -Vf) / If = R. R is the value of the current limiting resistor needed for the LED. My feeling is you don't have enough current to the LED with your existing circuit.

Without an opamp circuit on your phototransistor output, the output's going to be more analog than digital. Might be causing issues with the signal levels needed to trigger the MS. And if the collector current isn't getting high enough (LED not bright enough for example), the phototransistor may not be pulling the output all the way down to ground.

Is both the 5v power and ground from the MS?

Also, is it set up for "Rising Edge"?

[juki48]

when I re-built and tested the sensor I ended up removing the 510 resistor and put a 330 in series of the LED instead of the 1k. I used the 1k as pullup for the photo transistor. I am using the 5v ref and sensor ground from the ecu. this is the LED I got OP298B http://www.optekinc.com/datasheets/OP290SERIES.PDF. looks like I could put alot more current to it vs the 15mA it is getting now, I just didn't want to blow it like I did the original Crane cams one. I have no idea what the crane cams led was. I did get matching photo transistors to the leds I got but the crane cams one still worked so I didn't swap that out.

[jhoefer]

Well, I'd try a 47 to 60 ohm resistor on the LED to see if the extra brightness helps any, but at this point I'd really like to see what the oscope says about the sensor output.

[juki48]

been messing with the scope, it's not a great one but it's better than nothing. channel 2 is the 5v ref and channel 3 is the sensor output.
here is a screen shot during cranking

this time it started

I seem to be getting a pretty good 0-5v signal.

I do not have any filtering on and I have it set to falling edge... edit, tach period rejection WAS on.
this is what it looks like cranking today, and of course it will start when I'm trying to figure out why it won't start

[juki48]

pulled out all the plugs to see if the compression was affecting the cranking pulse...

yep, it is.

[Piledriver]

To get mine to work properly I always had the filter "on"--didn't need to mess with it much more until I switched to Hall, that sensor could see an extra hole just off pattern, so I had to tweak on the filter so it would ignore it.

[jhoefer]

Of course the sensor starts working normally when you finally have some test equipment...

[Piledriver]

Of course the sensor starts working normally when you finally have some test equipment...

Of course, I usually call that "technician sensitivity", at least in polite company.
I see it all the time at work.