We have a BMW rally car on which we fitted a msq 1 v2.2, the car has all the electric circuitry made from scratch and we verified all the circuits before installing the megaquirt in place.The +12v feed from the battery goes through a general circuit breaker (for safety reasons) and then to the fuse and relays panel, megasquirt has it's own relays including the main relay which feeds +12v to megasquirt and a fuse for the main +12v feed to megasquirt. After testing the circuitry we fitted the msq in the car and the car started right away, so we started to test the functionality of the circuit breaker while the car was on, we flipped the circuit breaker on OFF position and the engine and all other electrical components turned off as expected, but when we tried to start the car the second time the injectors were stuck open, we diagnosed the board and found out that the injector driver circuit was the culprit and repaired it. We diagnosed all the electrical circuitry on the car once more but we didn't find any problems, so we tried again... on the second try and the same scenario, again the injector driver circuit was damaged mainly U7 and sometimes Q2, Q7 or Q1 were damaged, we already repaired one v2.2 board for two times already, but the third time tuner studio wasn't able to communicate with megasquirt, so right now I need to diagnose that as well ...
Do you have any suggestion on what causes the v2.2 board to crap itself out just by cutting the +12v feed from the battery, or how to optimize the circuit breaker so in the future we won't be able to damage the engine management ?
Best regards,
m3ltd0wn