Expected EDIS/MJLJ voltages

[MartinM]

I though it might be useful to measure and document the cranking voltages around my working system to potentially help others with installation problems.

I disconnected the plug from the coil to stop the engine (Peugeot 205GTi, 1580cc, OE fuel injection and MJLJ v3 with MAP sensor) and cranked the engine on the starter motor.

Battery voltage was about 12.3v and I used an auto-ranging digital multimeter on DC and AC voltages.

VR sensor - measured across EDIS pins 5 and 6 at the main connector with the connector disconnected from the EDIS ie this is the open circuit VR sensor voltage:
- 0 volts AC stationary
- 2.3 volts AC cranking
Explanation: VR sensor produces a +ve and -ve swinging AC voltage as a result of the ferrous teeth of the trigger wheel passing close to the magnet at the end of thw sensor. Wire wrapped around the magnet picks up the change in magnetic field and converts it to an AC voltage - just like a motor in reverse, really
Demonstrates: A working VR sensor

PIP pulse - measured at EDIS pin 1 with the main connector connected to EDIS:
- 12.3 volts DC stationary
- 5.4 volts DC cranking
Explanation: The PIP pulse produced by the EDIS is a 1:1 mark/space ratio 0v to 12v pulse train with a frequency proportional to engine rpm. When measured with a DC voltmeter, the voltage measures around half the supply voltage, which seems reasonable given the 1:1 mark/space ratio.
Demonstrates: A working VR sensor and a probably working EDIS module with regard to generating PIP pulses

SAW pulse - measured at EDIS pin 3 with main connector connected to EDIS and MJLJ SAW output connected to EDIS:
- 0 volts AC stationary
- 0 volts DC stationary
- 0.14 volts AC cranking
- 0.06 volts DC cranking
Explanation: The SAW pulse produced by the MJLJ is a 1:lots mark/space ratio pulse train with a mark/space ratio that increases as timing tends towards TDC and an overall frequency proportional to engine rpm. When measured with a voltmeter, the voltages are very low since the pulse train is at 0v for most of the time. I don't really know why the voltage appears higher on the AC range!
Demonstrates: A working VR sensor, a probably working EDIS module with regard to generating PIP pulses and a probably working MJLJ with regard to producing SAW pulses

It would be useful if someone else could do the same tests to verify these figures - post the results here please.

[T3tone]

Top stuff, very helpful post for peeps (like me) doing a new install for the first time.Many thanks.

[Dimbit]

I made the same measurements with the engine running on the old coil&dizzy and found most were roughly the same, although my VRS signal was more like 1.7V. These numbers were very useful for testing/troubleshooting. Maybe they should be publicised a little harder?

[MartinM]

VR Sensor voltage is highly dependent on:
- sensor <--> wheel distance
- rpm

....so some variation is inevitable. The best summary is that it's "in the order of volts", so if you measure zero or close to zero, something's wrong

[Dimbit]

One thing I forgot to mention that I found a useful check was measuring between coilA&B pins and battery +. this should (and did) appear non-zero and non-12v when cranking and tells you for sure that the coils are being fired.

[alexander]

martin, you should update one of the guides eg Vehicle Installation Guide on the http://www.autosportlabs.net/Main_Page
page, with your results. a few months into the future, and this thread will be lost in history.

alexander.