3304 & 3306 – Fuel Flow With Engine Running

4. Priming pump. 5. Fuel injection pump. 7. Bleed valve. 19. Shutoff solenoid. 20. Position for oil pressure shutoff (attachment). 21. Fuel ratio control. 22. Brass screw terminal. 23. Position for measurement of fuel pressure in housing. 24. Filter base. 25. Timing pin in storage position. 26. Drive sleeve. 27. Governor control shaft. 28. Cover for high idle stop and low idle stop. 29. Position for using timing pin. 30. Cover for housing. 31. 2P8315 Bracket Assembly. 32. Transfer pump drain. 33. Inlet for lubricating oil for automatic timing advance unit.

When the engine is running, transfer pump (18) pulls fuel from fuel tank (10), through fuel filter (11), and into channel (12) behind cover (30). From the channel, the fuel goes through check valve (13) into the bottom of priming pump (4), through the priming pump, out check valve (14) and into passage (34) in the housing. The fuel in the passage is the supply for transfer pump (18). The output of the transfer pump goes into housing (15).

12. Channel. 30. Cover for housing.

The fuel in the housing is the supply for the injection pumps and the lubricant for all the moving parts in the housing. Fuel can go from the housing in three ways.

5. Fuel injection pump. 16. Check valve. 17. Bypass valve. 34. Passage (to transfer pump inlet). 35. Passage to check valve.

1. Fuel injection pumps (5) send some fuel to the cylinders during injection.
2. Constant bleed valve (1) lets approximately 9 gal./hr. of fuel go back to the fuel tank, through return line (8) when the pressure in the housing is 25 to 32 psi (170 to 220 kPa). This flow takes air and heat away from the housing.
3. Bypass valve (17) keeps the pressure of the fuel in the housing at a maximum of 25 to 32 psi (170 to 220 kPa) at 2200 rpm. Fuel which goes through the bypass valve mixes with the fuel flow from the tank in passage (34). From here the mixture of fuel goes through the transfer pump and back into the housing.

1. Constant bleed valve (in fitting).

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