T550 won’t crank, fuel losing prime

[chance_pittman92]

2014 T550 has been running fine then got to where if I shut it off it had to sit for a few hours then be primed to start back up. I have replaced fuel pick up tube, fuel line and primer bulb, filter, and o ring on bleed screw. When I prime it up it will turn over but not start and then I check the primer bulb and it isn't hard anymore and there is air in the lines again. Occasionally when the stars align it will crank and runs excellent but if you shut it off it goes right back to air in lines and not cranking. I can't find any leaks anywhere. What am I missing? Fuel solenoid?

 

[Bswwood]

You may not be loosing prime but rather not building enough rail pressure to start engine due to internal wear in injectors. However once it starts it will run fine because it has the RPM and power to meet fuel demand assuming this is the Doosan D24 engine. When it wont start, unplug the sensor on the end of the fuel rail and try to start engine. It will not start but listen to see if engine starts to try harder, or RPM slow, like a load is on engine. By unplugging sensor the fuel system will default to max pressure, around 30,000 PSI and really load the engine. If you hear no difference on starting RPM then its possible the injectors are leaking by beyond spec. Then you would do an injector leak test. Also the primer will not stay hard after you turn the engine over a few times, this is normal.

 

[salcidoariel81]

You may not be loosing prime but rather not building enough rail pressure to start engine due to internal wear in injectors. However once it starts it will run fine because it has the RPM and power to meet fuel demand assuming this is the Doosan D24 engine. When it wont start, unplug the sensor on the end of the fuel rail and try to start engine. It will not start but listen to see if engine starts to try harder, or RPM slow, like a load is on engine. By unplugging sensor the fuel system will default to max pressure, around 30,000 PSI and really load the engine. If you hear no difference on starting RPM then its possible the injectors are leaking by beyond spec. Then you would do an injector leak test. Also the primer will not stay hard after you turn the engine over a few times, this is normal.

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