Dead mcp3208 -SOLVED-

[Ignitec]

Can cranking with low battery kill mcp3208? After draining my bat (left lights on far from home...) I tried to crank, engine struggled to make few revolutions, flooded cylinders and mcp died. I thought one of FETs died, but they are all ok. All input channels now shows 5v.

Another pretty strange thing happened: lambda target moved away. In lambda target is 1, but on gauge in VT it shows 0.88. If I change table to 1.25, on gauge is 1... An hour before everything was fine. Could anything other smoke to cause that behavior?

[mattias]

No, this shouldn't happen.

Is there detailed information about your setup anywhere?
Do you have a project thread here? http://www.vemssupport.com/forum/index.php/board,2.0.html
Or a Wiki page? http://www.vems.hu/wiki/index.php?page=MembersPage

[Ignitec]

No, i still didn't described my car detailed nowhere, but I think I figured out what might happened. I have 3 inputs configured (launch control, shift cut and dual config). In moment of cranking there was config B switch active, and I connected ground for switches on chassis near handbrake, far far away from engine ground... Might this be reason? Some ground potential differences while cranking...

Last one on this page
http://www.vems.hu/wiki/index.php?page=MembersPage%2FIgnjatRNN

[GintsK]

No, i still didn't described my car detailed nowhere, but I think I figured out what might happened. I have 3 inputs configured (launch control, shift cut and dual config). In moment of cranking there was config B switch active, and I connected ground for switches on chassis near handbrake, far far away from engine ground... Might this be reason? Some ground potential differences while cranking...

Last one on this page
http://www.vems.hu/wiki/index.php?page=MembersPage%2FIgnjatRNN

Most probably this was the reason. Safest way is to use same ground as sensors. Chip is very sensitive.
In older units has no any protection for ch6 and ch7. Later in-line diode was used for those.

[Ignitec]

I'm almost sure that's the reason because there couldn't be anything else. All grounds are more than good, all wires 0.75mm2 or more, all contacts perfect clean, this is the only thing that could be. I cranked it once before with almost empty battery and nothing bad happened, but then there wasn't any active switches.

Now, only thing with lambda target confuses me... Before this, lambda target on gauge was always same like in table, now it's about 20% richer then lambda target table. If I set 1 in table, i have 0.88 on gauge, if I set 1.25, then i have 1 on gauge...

[GintsK]

EGT safety feature makes lambda target richer. Your EGT reading probably is 1024degC. Right?

[Ignitec]

Haha, yes :) 1200 all the time!

Thank you!

[Ignitec]

Changed mcp3208 and wired grounds for switches on same place like vems and everything is okay for now.