Hello from Manitoba.... 1988 mack R688ST with a E6 350 Took in shop for a miss, cracked lines and sure enough #6 dead in the water. Tested injector and fail....6 new injectors and fuel lines later reassembled still a miss. Cam is good, compression good.... Noticed when cracking fuel lines #6 looked (foamy) yup I said foamy.... Now I don't know my mechanical injection pumps. When these pumps wear out .... Is it possible that # 6 line hasn't got the pressure to fire the injector? Is this common to pump failures..... Little History of truck..... Literally sat and did not move for 3 years in a Quonset. Shouldn't matter but thought I'd point it out.... Thanks in advance.... Love the forum by the way... Colin