The 767 with the C6-80C2 Engines which have FADEC control has a combustion chamber pressure limiting function internally within the Electronic Engine Control (EEC) Unit which limits the Combustor to 430 psi relative to under-cowl pressure.
This is achieved by a sensing line from the combustor area providing a pressure signal to a transducer in the EEC.
The EEC will then down-trim fuel scheduling to prevent overpressure conditions occuring.
With "AUTO" selected on the Eng Start Panel, this will enable the Ingitors to operate automatically when either the leading edge slats are not fully retracted or if Eng Thermal Anti Ice (TAI) is selected on.