Need ideas on EDIS/Megasquirt problem

[speeder]

I have been trying to work a frustrating problem with my LT1 with EDIS-8/ MS1 project.

 

The car will start, run for about 1 second, then quit.

 

Scoping the pin 5 VR sensor input to the EDIS I see about a 10 volt peak - to - peak signal, centered on ground. The edis outputs a PIP signal for about 1 second, then the PIP goes static. I have the spout plug pulled to eliminate any Megasquirt influence on the ignition module.

 

I swapped EDIS modules and VR sensors out with no change. I monitored battery voltage at the EDIS and see a small drop while cranking, but it doesn't go below 10 volts.

 

I took a spare trigger wheel and spun it at 200 rpm on a drill press, then cabled its VR to the EDIS and the PIP stayed up, and triggered the Megasquirt reliably. Note that this was with all wiring on the car as originally tested, just the sensor and trigger wheel substituted. The wheel and sensor on the car have no obvious problems evident (runout checked to be 0 and the cable substituted), and the sensor gap is set to .030.

Are there any sensor/wheel considerations that may cause this problem?

 

Nothing like something like this to make you feel stupid...A previous installation I did very similar to this one went off without a hitch.

 

Can anyone tell me what's a good signal level from the VR sensor? I seem to remember that when the PIP was present the VR signal was higher, maybe like 16 volts peak - to - peak, then the signal dropped down at the same time the PIP disappeared. I'll go back tomorrow and measure the signal from the drill press wheel to compare.

 

Any other ideas?

[z-ya]

Rick,

 

Are you using a stock Ford trigger wheel on the car and the drill press? Does the VR sensor output look the same on the scope when running on the drill press as when on the engine?

 

The VR signal is supposed to look something like this:

 

 

There is a 0.5V hysteresis so that the EDIS module ignores the VR sensor output until it crosses 0.5V. Is the VR output 10Vpp?

 

I would trigger the scope on the voltage droop on the EDIS module and look at the PIP output with the other channel. If it looks like the PIP output goes off consistantly after the voltage droop, then it is most likely the EDIS module resetting. Try running the EDIS module off a different +12V source, or put a stout battery charger on the main battery.

 

Let me know how you make out.

[speeder]

The VR output is 10V p-p, but seems to be bigger when the car runs.(?)

I didn't know the zero crossing hysteresis level, but did suspect it is pretty small. That VR signal should be more than sufficient.

 

I agree that the EDIS Module is probably resetting and will investigate that today. It's really strange that when the wheel and VR are operated off the car everything works, though.

 

I did put a big filter capacitor on the module's power wire to no avail., and see no noise on the 12V line.

 

Pete, ditto on good to meet you at the convention... It's always good to find another electronics geek:mrgreen:.

 

I'm going to spend the day at the shop - need to get this car done - will monitor this thread for any more ideas.

[speeder]

Found it. The problem was a partial short form the - wire to shield in the cable to the VR sensor. Not a connection, it was in the middle of the cable. First one of these I've seen. I didn't think to check the signal on the negative side also - It's a differential input to the EDIS. "Doh!" he says as he slaps his forehead...

 

The VR signal is about 5v p-p while cranking, and when the engine starts it goes to 16volts plus at idle.

 

The misery with this car continues... when it finally started that was the starter's last gasp. Before I can continue tuning it must be replaced. This car needs an excorcism.

[Scottie-GNZ]

This car needs an excorcism.

Make sure you drive out all the demons before you turn it over to me

[z-ya]

The chances of having a bad piece of shielded cable is rare. Consider yourself lucky (or not)

[speeder]

The chances of having a bad piece of shielded cable is rare. Consider yourself lucky (or not)

 

Well, I made this harder than it could have been, as when I swapped the sensor cable during troubleshooting I managed to reverse the + and - wires. There is still a signal (the wrong one) on pin 5 this way - Double Doh!

 

Maybe I shouldn't be telling of dumbass screw-ups like this...

 

Scottie, I'm cautiously optimistic that it will be cleansed by the time you get it.

 

For you others who are following this, Scottie will get the car next for the installation of a huge turbo. Power expectations are big - we're bringing it up with 65 - pound injectors:shock:.