Microtech missing pins on harness?
05-24-11, 06:25 PM
#1
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missing pins on harness?
Hello, I have a few questions about my LT8 harness, I recently purchased a harness off of someone who said it was off there last car. the harness is wired for my LT8 ecu but I have noticed a couple pins/wires on the harness are missing compared to the ECU diagram pinout for the LT8, I have attached an image of the diagram with a red X showing which wire/pin I am missing on my harness and wondering how crucial this is. I am experiencing no spark coming from my trailing coils and am curious if this could be related to that.
https://i52.tinypic.com/24yn7n6.jpg
https://i52.tinypic.com/24yn7n6.jpg
05-24-11, 09:28 PM
#2
talking head
power and the ignition ground being missing is a bit of a worry
take the cover off the ECU,, see if the ground pin inside are bridged to the other ground
and the pink ( IG ) bridged to the red ( power )
i suspect they are ( for it to turn on ) but that is NOT the way to get theECU consistant as it uses the red wiring off the battery to drive the injectors and they are ballasted by the battery acting like a big cap
if running off the pink wire only i suspect the voltage will go up and down with injector demands
-not good,, as voltage does not have a correction map in a micro
as for the ignition bundle earth,, i would add that back in,, that one MUST go to the engine block,, else ground loop will make for noise
( i would suspect that the other earth is tied instead to the engine )
me,, i would buy a 2 or 3 pin plug with similar pins ( for the pins ) and jack them back into the microtech plug and wire them to battery and to engine block
and cut any internal bridges
---
they are not part of your missing trailing spark ( which is normal when cranking a micro )
but missing or internally bridged they will make for voltage supply and RFI issues
take the cover off the ECU,, see if the ground pin inside are bridged to the other ground
and the pink ( IG ) bridged to the red ( power )
i suspect they are ( for it to turn on ) but that is NOT the way to get theECU consistant as it uses the red wiring off the battery to drive the injectors and they are ballasted by the battery acting like a big cap
if running off the pink wire only i suspect the voltage will go up and down with injector demands
-not good,, as voltage does not have a correction map in a micro
as for the ignition bundle earth,, i would add that back in,, that one MUST go to the engine block,, else ground loop will make for noise
( i would suspect that the other earth is tied instead to the engine )
me,, i would buy a 2 or 3 pin plug with similar pins ( for the pins ) and jack them back into the microtech plug and wire them to battery and to engine block
and cut any internal bridges
---
they are not part of your missing trailing spark ( which is normal when cranking a micro )
but missing or internally bridged they will make for voltage supply and RFI issues
05-24-11, 09:55 PM
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the thing I dont understand about the "power" wire (red one) is why would there be two? if you look to the left on teh diagram of that one there is a "batt" wire which I have connected to constant 12v, are why are two contstant 12v+ power sources?
as for the grounds, I will go rob a connector for a pin to ground the ignition plug ground, A quick question for the other grounds on teh pinout are those neccessary to go to the engine block too, because atm I have them grounded to the chassis
thank you once again
as for the grounds, I will go rob a connector for a pin to ground the ignition plug ground, A quick question for the other grounds on teh pinout are those neccessary to go to the engine block too, because atm I have them grounded to the chassis
thank you once again
05-24-11, 10:34 PM
#4
talking head
you are correct about the power down at the CAS input end of the plug
in later ecus it is listed as " power,, not connected "
and i see that the pin is provided for those ECU's that must drive a hall effect sensor rather than the mazda VR
- so ignore it
also in earlier ( digi 2 etc ) ecus the grounds are tied all to one black wire
but i know this is revised for later ECU's to provide the ignition out bundle with its own earth to the block to circumvent some noise issues in the earlier machines
i would be hooking that one up,,,
as the noise thing can be a very persistent intermittent issue that can cost the engine if unlucky
you should be doing everything you can passively to minimise the potential for this issue
that includes the correct earths ,, and even sometimes adding shield and twisting the cas signal wiring
the ground in ignition bundle goes to block
the ground in the other harness goes to the battery ,, or main chassis earth point if that is too far away
in later ecus it is listed as " power,, not connected "
and i see that the pin is provided for those ECU's that must drive a hall effect sensor rather than the mazda VR
- so ignore it
also in earlier ( digi 2 etc ) ecus the grounds are tied all to one black wire
but i know this is revised for later ECU's to provide the ignition out bundle with its own earth to the block to circumvent some noise issues in the earlier machines
i would be hooking that one up,,,
as the noise thing can be a very persistent intermittent issue that can cost the engine if unlucky
you should be doing everything you can passively to minimise the potential for this issue
that includes the correct earths ,, and even sometimes adding shield and twisting the cas signal wiring
the ground in ignition bundle goes to block
the ground in the other harness goes to the battery ,, or main chassis earth point if that is too far away
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