I'm sorry if this tread was already discussed but I couldn't find any answers for it.
I have a 2WD Sierra with MSD chip installed on it (ALS and LC), stage 1.
It's been already couple months like I'm fighting with weak voltage on ECU. Stu from MSD has been a real help but I just can't ask him directly with every problem I have

I have started my fight with voltage as weak as 11.8 on ECU under high pressure. After I removed orginal immobiliser and alarm, clean connections, made additional earth strap directly from battery and make new wiring for fans with separate relay for each fan I have found that ECU on idle (cold engine) has fallowing voltage:
everything turned off - 13.98V
with light ON - 13.71V
with light ON and one fan - 13.54V
with light ON and two fans - 13.36V

On battery I have fallowing results:
with everything OFF - 14.26V
with light ON - 14.08V
light + fan1 - 13.89V
light + two fans - 13.70V

When I turned ON absolutely what is possible to turn ON I had voltage on battery as weak as 12.8V.

I have checked all the basic fault according to this tread:
https://passionford.com/forum/genera...-readings.html
and the only one I have found is weak voltage on ignition trigger, pins 24 and 25. According to the tread mentioned above i should have at least 4.5V while I have 3.42V

The questions is:
1. Is the voltage OK and if not where is fault? Alternator has been renewed last year!
2. How to solve weak ignition trigger weak voltage?
3. What voltage should I expect when lights and fans are ON?

Will be glad for help!

 

I don't know if those voltages would cause a problem, but :

have you replaced the large wire from the alternator to the battery ?

have you replaced the fuseible links that feed the fuse box (and everything else) ?

 

Those voltages are excellent, NOTHING wrong at all.
Can't comment on how sensitive or otherwise the ecu is voltage wise on the pins you mention though.
tabetha

 

Those look better than ok to me, i don't think mine has ever seen above 12.7V with nothing on.
On a mission to sort it out soon though.

 

According to STU from MSD I should have 13.7V+ at all even on the high pressure, if not ecu will be on the wrong site of the map.
How can I have such a voltage while on the battery I have low?
Today I will check the voltage on high revs.
BTW what can cause weak voltage on ignition trigger?

I haven't replace the cables from alternator and to fuseible links.

 

i cant be arsed with the ford wiring problems i just wired my fans in new and my ecu feed dont both with the 20year old fusebox!

13.8volts at all times i would say is virtually impossible.

 

VERY unlikely to get that out of the alternator, even with no load on, most are pegged at around 13.4, but they do vary a bit, not normally as high as 13.7, some other cars run much higher, some vaux can be up to 15.8V, esp if on Calcium battery.
I'd be well happy with those figures.
tabetha