John Deere 4720 return fuel leaking into base

[flybikedave]

My 4720 was under 6' of flood water and I'm trying to get it going again. The entire south Louisiana area was flooded and mechanics are booked up and I desperately need to get this machine back to work. After draining oil and water from base, I removed the exhaust manifold and valve cover and by depressing back side of rocker arms to open valves, allowed water to bleed from top of cylinder chambers. Working slowly, turning the engine by hand, all water was eventually drained from the combustion chambers and I was able to use the starter and start the engine. Problem: My return fuel is not returning to the tank, but is filling the crankcase. Earlier, before depressing valves to remove water, I was hoping to remove the injectors, and I had loosened the injector hold down tabs, but then abandoned that idea when I saw how difficult it would be to remove the injectors. Unfortunately, I forgot to tighten the injector hold down tabs before trying to start the engine. I saw the injectors move as the engine rotated and then I torqued them back down. The engine started and ran good, but I fear I have damaged the return fuel lines but don't know how to proceed. I would love to see a diagram of the fuel pressure and return lines, which mostly appear to be located inside the engine. Maybe I missed something on reassembly, but I'm fearing the worst, and would appreciate any guidance from an experienced 4720 mechanic.

 

[Tx Jim]

Did you loosen injectors(key 15) or pumps(key 19? Leaking inj seals should blow fuel & compression back up inj mounting hole in cyl head.

 

[flybikedave]

Did you loosen injectors(key 15) or pumps(key 19? Leaking inj seals should blow fuel & compression back up inj mounting hole in cyl head.

Looking at the diagram, it appears I loosened the hold down tab for the injector pumps, (19) because they were moving up and down as cam turned, They are still working and engine ran, but then filled with fuel, so I thought maybe I cracked a fuel line with the movement.

 

[flybikedave]

It was running when fuel started blowing out of the valve cover vent. I shut it down and checked the oil level, which showed full of fuel. I can't believe it was running like that, but obviously, I've screwed up. Will drain again and make certain excess fuel is not on top of piston before proceeding, but do you have any idea where the fuel came from? I don't see return lines in your diagram. Thanks Jim

 

[Tx Jim]

I looked for return lines in parts schematics but saw none listed. Is your tractor OS or cab type? I think the pumps will have to be removed and new seals installed to stop fuel from getting into engine crankcase.

Update: I located fuel return line(key 2 & 6) for OS model.

 

[flybikedave]

I looked for return lines in parts schematics but saw none listed. Is your tractor OS or cab type? I think the pumps will have to be removed and new seals installed to stop fuel from getting into engine crankcase.

Update: I located fuel return line(key 2 & 6) for OS model.

I have a cab type 4720. I can't make out much from that partial diagram. Can't figure where the line is connected to and from? I ordered a service manual and hopefully will learn more. Just still hoping a return line is not connected. I appreciate your efforts to help.

 

[Tx Jim]

Return line on cab type is key 2 & 6. I can determine where return line attaches to fuel tank but I can't determine where(how) it attaches to IP or inj.

 

[flybikedave]

Return line on cab type is key 2 & 6. I can determine where return line attaches to fuel tank but I can't determine where(how) it attaches to IP or inj.

Just wanted to follow up to thank you for your help Jim. The leaking fuel problem was an injector pump that had become dislodged when I had the hold down clamps loose. I had tightened the clamps back up, but one of the pumps was not fully seated, allowing fuel to leak past the o-rings into the base. Engine running fine now, but having hydrostat problems now. In the process of going thru all applicable electrical connections to eliminate water/corrosion issues. Thanks again for your help.

 

[Kyle_in_Tex]

Just wanted to follow up to thank you for your help Jim. The leaking fuel problem was an injector pump that had become dislodged when I had the hold down clamps loose. I had tightened the clamps back up, but one of the pumps was not fully seated, allowing fuel to leak past the o-rings into the base. Engine running fine now, but having hydrostat problems now. In the process of going thru all applicable electrical connections to eliminate water/corrosion issues. Thanks again for your help.

Make sure the electrical pickups on the pedals are clean and dry.