The FIA has acted on a fuel system 'cheat' which is thought to be giving some teams an unfair advantage.
The move follows claims that Mercedes and Ferrari, in particular, have devised a system whereby they can feed more fuel through the sensor than is required and then storing it ahead of the fuel injectors.
Consequently, when a boost in performance is needed the excess fuel is fed straight in to the injectors thus allowing the unit to exceed the 100kg/h limit.
"With immediate effect we will expect fuel pressure, in the high and low pressure systems, to remain constant above a flow rate of 90kg/hr," wrote FIA race director Charlie Whiting in a note issued to all teams at Barcelona.
"We do not consider it necessary to define here what we consider constant, we feel it will be more practical to discuss any concerns we have with the relevant team(s) if and when issues arise.
"We will also be carrying out careful physical inspections of all fuel systems in use," he warned.
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