Been doing some tests and Engines will not start after pressing 'CTRL + SHIFT + F1' so then pressing 'CTRL + SHIFT + F4' away they go.

Looked at these parameters in all my saved B77x *.FLT Files. They are the same for all saved "cold" situations but some tags vary to other situations (understandable) including CS's default flight - 777-200 Cleared for takeoff (KSEA).FLT where you will note the mixture is near unity:

[Engine Parameters.1.0]
ThrottleLeverPct=0
PropellerLeverPct=0.99371337890625
MixtureLeverPct=0.99615478515625  //THIS ONE
Pct Engine RPM=1.2869414382895356e-005
MaxReachedEngineRPM=21507.107467776317
LeftMagneto=True
RightMagneto=True
GeneratorSwitch=False
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=False

[Engine Parameters.2.0]
ThrottleLeverPct=0
PropellerLeverPct=0.99371337890625
MixtureLeverPct=0.99615478515625
Pct Engine RPM=1.2869414382895356e-005
MaxReachedEngineRPM=21507.107467776317
LeftMagneto=False
RightMagneto=False
GeneratorSwitch=False
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=False

After I change the MixtureLeverPct=0.996 to zero then I have to do the 'CTRL + SHIFT + F4' thingy. Some of you guys have based your start up procedures on the default C172 (which I have never done) therefore your mixtures will not be maximum. Try basing your cold default situations on the CSB77x with these parameters.