No Trigger

[eman911]

I've repaired the broken wire, phased input and output on the dizzy and have a switching signal (.3-.8v) on pin 24. I still do not have a trigger signal and the logger still reports "empty read". The MS board has been put up to the latest spec using the manual above. It functions perfectly on the JimStim, and the logger registers the trigger signal. What's next?
IGNORE THIS POST IT IS IN ERROR, SEE BELOW

[eman911]

I have repaired the distributor wiring, set the distributor phasing and tested with no luck. The logger still shows no trigger, and re[ports "empty read". Power, ground and signal wires are good. With the MS plugged in I see a switching 3.7v (window) and 5v (vane) on the signal wire. I currently have a 560 ohm pullup to 5 v. Is this enough of a voltage change to trigger the MS? If not do I need a bigger pullup? If so, how big?

[eman911]

Or do I need to adjust R56 from 2.5v to something higher?

[DaveEFI]

Not knowing anything about your actual hall sensor, I'd lash up something like a 5000 ohm linear pot as a temporary pull up resistor and adjust it for the best differential voltage between tooth and land. With 5v, should be about 2.5v minimum. After finding the best compromise, very carefully disconnect the pot and measure it. Use that value for your fixed resistor.

Then adjust R56 (if still no tach to MS). Start fully clockwise, then a turn clockwise and check again. And so on.

However,being able to see the signals on a scope would make things a lot easier. You should get a (near) perfect square wave from a hall sensor.

[billr]

"With the MS plugged in I see a switching 3.7v (window) and 5v (vane) on the signal wire."

If that is still your voltage swing, no it isn't good. The "low" needs to get much closer to 0V. Weren't you "bench testing" the dizzy/CKP alone before, and couldn't get a good "low" that way? There is no use connecting it to the MS until this (no low from dizzy) is resolved. Did you ever try a pull-down resistor in place of pull-up? Was that clear: if you try a pull-down, remove all pull-ups.

[eman911]

Bill, the last pullup tests I did was prior to revamping the board to the current build spec.I also had some reliability issues with the distributor connector which have since been solved. I'm kinda back to square one (maybe 20). I used the 560 ohm pullup at James' suggestion. I have not tried a pulldown at all.

Part of my problem is that I don't know what exactly the MS wants to see, I assume by your post as near to 5v-0v as possible, or the best way to get there. When I adjusted trimpot (r56) to 2.5v am I telling it I want to see a voltage drop of 2.5v or that I want to see the voltage drop below 2.5v?

I feel that I am tantalizingly close.

[jsmcortina]

I assume by your post as near to 5v-0v as possible, or the best way to get there. When I adjusted trimpot (r56) to 2.5v am I telling it I want to see a voltage drop of 2.5v or that I want to see the voltage drop below 2.5v?

The 2.5V is the threshold. Below 2.5V is treated a 0V. Above 2.5V is treated as 5V.
With a hall sensor input you should be able to rotate the engine by hand and measure the voltage on the signal wire. With the ECU turned on you should see it change between near 5V and near 0V.

James

[eman911]

Got it. Needed 10k pullup. Working as it should now, thanks to all for your help!