New user here with a couple questions.
I've got a skidsteer loader with a Isuzu 4Jg1T engine and I cannot find much info on the web to service it. The engine developed a knock on the number 4 cylinder and I thought it was a bad valve so I pulled the head and found no valve problem. The engine is also low on power runs rough. I've sent the injectors off and they've got some slight issues but nothing that should've caused a knock. So, now I'm thinking injection pump and have the following questions. I should add, the reason i'm suspecting fuel is because the #4 head area has significantly less soot on the combustion/valve surface whereas the other 3 cylinders have a fairly uniform layer of soot across the combustion surface. The #4 head combustion surface is almost shiny metal with no oil and very little soot.
I'm no mechanic so I'd appreciate any troubleshooting/repair guidance
Questions:
1. Can the head gasket be reused?
2. Does the valve cover gasket require sealant or is it meant to be used dry?
3. How is the injection pump timed?