Hi we need help with a changfa 1115 purchased new 3 years ago and it has just sat since then. My son started a new project and is using the engine but we have been unable to get it started. He has fuel to the fuel pump but can't get it to pump to the injector assembly. He cleaned the delevery holder ,spring ,ring ,seat and pump element {Plunger and barrel } the assembly moves good but it still wont pump. He tried to remove the pump assembly but it would not come out easly it wants to twist so he tightened it back up. Does the pump just unbolt and come out or do you have to take something else aloose to take it out. Or is he working on the wrong thing. He belives the pump is the problem.