Injection advance device

In a fuel injection pump for use in a diesel engine, said fuel injection pump including a pump housing defining an interior pump chamber, said housing containing a feed pump for supplying fuel under pressure substantially proportionally to engine speed to said pump chamber, and a fuel-injection timing control member movable to determine a fuel-injection timing corresponding to its position, an injection advance device comprising:

• (a) a casing fixed to said pump housing;
• (b) a cylinder slidably located in said casing to form first and second chambers at the respective ends of said cylinder, said first chamber being in communication with said feed pump inlet side and said second chamber being in communication through a release passage with said feed inlet side;
• (c) first spring means located in said second chamber for urging said cylinder toward said first chamber so as to advance the fuel-injection timing;
• (d) a piston slidably located in said cylinder to form third and fourth chambers at the respective ends of said piston, said third chamber communicating with said feed pump inlet side, said fourth chamber communicating with said pump chamber, said piston being drivingly connected to said control member;
• (e) second spring means located in said third chamber for urging said piston towards said fourth chamber;
• and
• (f) valve means provided in said release passage for interrupting communication between said second chamber and said feed pump inlet side so as to prevent said cylinder from moving towards said second chamber in response to at least one engine operating parameter.