Hi, I am new to this forum and hoping to get some ideas on what is going on with my 2003 Ford F650 5.9L Dump Truck. When I crank it it coughs. When driving down the road in low idle check engine light comes on and I cannot accelerate. When shifting to a lower gear the check engine light will shut off and recover. Loss of power under load. Black smoke when check engine comes on or when it runs over 2000 rpms. Cannot drive normal I have to shift at 1500 rpms before bucking. At this point it will not crank unless w-d 40 is sprayed into tank. Any ideas from anyone? If you need more info I will provide it. Thanks for your help.