Engine runs great when cold, but really rough when hot

[marndin]

I know it's not very clear but, there is air entering the filter (RHS) from the tank. As the engine is put under load it progressively gets worse. Until there are many small bubles entering the filter and large bubles coming out of the filter. Hope that helps, and thanks for any suggestions.

 

[Halftrack]

From past experiences and from other threads, I have found that diesel fuel contaminated with gasoline will produce the effects you observed. You say this has gone on for 3 months, has the fuel supply been the same during this time. If so. obtain new fuel from a different source and drain the tank as best you can. Refill with the new fuel and try it. Its a cheap remedy and may be the problem. The bubbles you see may be the gas vaporizing and causing a vapor lock. If you put some of the contaminated fuel in a shallow pan you can usually smell the gasoline vaporizing.

 

[ruffdog]

Good point. With many fuel related problems, I like sticking a hose to the bottom of the tank and siphon some out in a clear container just to see if it is contaminated. Over the years, it is amazing what I've seen. The neighbor's Allis WD had a thin brass shim that was floating around in the bottom of his tank. Once it would cover the outlet, the tractor would run out of fuel. Then the shim would float away and it would be fine for a while.

 

[marndin]

Good idea, but I can confirm that the fuel is fine.

 

[ruffdog]

Then it sounds like you just have to check the fuel line between the tank and filter for cracks or voids letting air in.

 

[Gordon Gould]

If it was a hydraulic suction line I would spray some shaving cream on it and look for a place where it disappears as it got sucked in but I have no idea if this would be OK for the pump and nozzle components in a deisel fuel system.

gg

 

[Stimw]

Does the fuel line from the tank pull from the side/bottom of the tank or does the tank have a drop tube from the top?
I had an old gas Clark forklift with a drop tube that had a hole rusted in it and would not pull fuel properly.

 

[ruffdog]

Does the fuel line from the tank pull from the side/bottom of the tank or does the tank have a drop tube from the top?
I had an old gas Clark forklift with a drop tube that had a hole rusted in it and would not pull fuel properly.

The parts pictures shows 2 drop tubes from the top going through grommets. The OP will have to check the tractor in question. The top-inside of the tank is where condensation and rust happens.

 

[searcyfarms]

start spraying with starting fluid - be selective where you spray it and see if the engine changes, it will suck that in usually if there is an air leak and change speeds even on a fuel line

 

[CalG]

Seems like the lift pump might have a bad diaphragm or the lines leak. Could be any where, check them all.

 

[marndin]

Thank you for all your suggestions. I will look at it over the weekend. I am expecting the problem to be a leak somewhere in the pipe between the tank and the filter. One question. Are the pipes to the tank usually pushed on to the same kind fitting that the filter has for example?