Pneumatically controlled fuel injection system

A pneumatically controlled fuel injection system for an internal combustion engine having air induction passages defining a venturi portion and a manifold portion, said system including,

• a pneumatic fluid source,
• a pneumatically actuated fuel injector connected to said pneumatic source and in fluid communication with a source of fuel and with said manifold portion of said engine, said injector being operable to admit fuel to said manifold portion in response to a pneumatic control pulse,
• a control device communicating with said pneumatic source and with said injector including means for initiating said control pulse in response to a trigger signal and for sustaining said control pulse for a time interval inversely proportional to a bias pressure,
• trigger signal generating means connected to said engine and communicating with said pneumatic source and with said control device providing a train of trigger signals having a frequency related to engine speed, and
• bias pressure generating means communicating with said pneumatic source and with said control device including;
• a first pneumatic circuit portion connected to receive a signal from said venturi portion and adapted to provide a first output signal indicative of fuel requirement,
• a second pneumatic circuit portion connected to receive a signal from said manifold portion and adapted to provide a second output signal indicative of fuel requirement, and
• comparator means connected to said first and second circuit portions and to said control device providing said bias pressure proportional to one of said first or second output signals indicative of fuel requirement.