EDIS - SAW and PIP swapped.

[trakkies]

Having made up a new MS loom after changing from fuel only to EDIS, I made a mistake a 2 year old would be ashamed of. I swapped the SAW and PIP wires. It now runs after correcting this, but I've a feeling EDIS is in limp home mode, ie fixed timing. It's getting dark here so any further work will have to wait until tomorrow. But to save a sleepless night, could I have fried anything by doing this?

Other question - what are the symptoms if the sensor connections are reversed?

[LeslieTroyer]

if PIP & SAW are reversed - you won't have any RPM showing up in MT.

Les

[DonTZ125]

"(A) mistake a 2 year old would be ashamed of" - heck, when my little girl was 2, plugging things (bits of toys, not engine controllers) in backwards was pretty much SOP...

[trakkies]

if PIP & SAW are reversed - you won't have any RPM showing up in MT.

Les

Oh indeed. That's why it wouldn't run. But as I said it did after I'd corrected the mistake. But in EDIS limp home mode.

[FixItAgainTony]

SAW is an input signal, when it was conected to the TachIn on the board, it would not be a problem for the EDIS, as an input would be connected to an input with no pull up resistors, etc involved. As the PIP is now working (limp home mode works), I would doubt that there is any problem with the EDIS side of things. The EDIS modules are really tough units.

What board / processor type (MS-I or MS-II) and code version are you using?
How is the SAW output from MS connected to the SAW input of the EDIS?

http://www.megamanual.com/ms2/EDIS.htm
The manual indicates a direct connection from DB37 pin 36 (Ign)
"jumper JS10 to IGN (this uses the processor port for the SAW signal directly)"

The processor port cannot handle a 12v signal, and the PIP is a 12v signal. When the PIP and SAW were swapped, there was a chance that the processor port received a 12v signal which may have damaged it.

The assembly manual describes an alternate way to drive the signal, which is a little safer as the port is not directly connected to the outside world:

http://www.megamanual.com/ms2/V3assemble.htm#output

"Note: If you are using the high current driver circuit to control an ignition module instead of a coil directly (and don't want to use the processor port directly - i.e., you have not jumpered JS10 to IGN), you likely need to to add a pull-up resistor. This allows the signal to go both high and low, rather than floating and low). Also, the IBGT will invert the signal from the processor, so your 'Spark Output' setting will need to be reversed."

If this buffer was implemented, then the problem is more likely related to software settings.

- Charles.

[trakkies]

It's all working just fine now.

I thought when I'd built the MS II V3 I'd configured the jumpers for EDIS, but initially it was used fuel only. I removed it and checked things on my stim - and the ignition light wasn't on. On opening it up, there was no jumper from J10 to ign, so a higher power was looking over my shoulder when I assembled it. ;-)

I missed the bit about using the IBGT as a buffer when reading the manual. But since it's now working, I'll leave it as is. The connector between the EDIS and MS looms is polarised, so no problems at a later date if I have to change anything.

[FixItAgainTony]

Glad you were able to get it sorted out. Given the cost of the MS-II daughter card and the time required to get a new one, I am a little surprised that the documentation does not strongly suggest implementing the buffer. The polarized plug is a nice touch to eliminate the problem.

- Charles.

[trakkies]

Glad you were able to get it sorted out. Given the cost of the MS-II daughter card and the time required to get a new one, I am a little surprised that the documentation does not strongly suggest implementing the buffer. The polarized plug is a nice touch to eliminate the problem.

- Charles.

Yes - I'd have thought a warning about what might happen if the two were reversed wouldn't come amiss. Although of course I don't know for certain if it would have damaged the processor - luckily.

In my installation, the engine loom runs close to where I've sited the EDIS 8 unit, so it made sense to have the connection there. I used a good quality co-ax for the SAW and PIP signals to ensure a good screen - which is where the confusion arose, as they're not identified. All the other wiring uses the EDIS colours.

These are the connectors I used :-