Ransomes T51D/951D Batwing Mower, losing power under Load

[Soulman]

Hi

I have a query about an issue i am having with a Ransomes T51D/951D Batwing Mower with a 51HP Kubota diesel engine.

The mower cuts grass fine on flat going or going down a hill but going up against a hill, the engine comes under heavy load and power drops until i stop and then the engine will regain power again.

New fuel filters (pre filter and main) were fitted, checked that diesel cap valve was clean, checked that there are no fuel leaks etc, cleaned out air filter. The mower starts very easily and engine runs smooth.

Bit of a head scratcher this one, so any suggestions welcome from anyone that might have experience with these mowers.

Thanks
Soulman

[Jeremy Rowland]

Does this engine have a fuel pump to supply the fuel or is it gravity fed? If it has a lift pump then I would check that out.

Jeremy

[Whitlock 505]

Is the mower hydrostatic drive? Could be that the filters are blocked under suction load going up hill and draining the power of the engine trying to drive it forward hence no problem when on flat or going downhill as there is not as much demand on fluid to drive it?
Could be a stab in the dark as I'm not familiar with these mowers.

Ian

[Soulman]

Hi Ian and Jeremy,

Thanks for responding.

Ian, yes its has full-time-4-wheel hydrostatic drive, (2-wheel for transport), 15 cu.in front wheel motors, 12 cu.in rear wheel motors and then cross-flow parallel drive differential lock. Your theory is interesting. The cutting decks on this models are also driven by hydraulic motors.

Jeremy, yes there is fuel pump in this model and i will check that out but it appears to be generally ok.

Thanks
Soulman

[Soulman]

Thanks to everyone for their help, I will update when i resolve the issue.

[Jeremy Rowland]

Thanks to everyone for their help, I will update when i resolve the issue.

It would not hurt or be costly to try the engine on a gravity fuel feed then if that cures the issue you would know that the fuel lift pump would be the most likely culprit. Hope you get it sorted okay.

Jeremy

[Soulman]

Hi

I got to look at the machine at weekend. I observed the engine running for quite a while and noticed that an air pocket exists in the diesel pre filter which sits vertically. ie fuel tank line is connected to the bottom of the filter housing and the other end goes to the electric fuel pump. Its a clear plastic housing with a filter membrane inside but there is a air pocket at the very top of the filter. I guess there should be no air in there?

Thanks
Soulman

[Jeremy Rowland]

Hi

I got to look at the machine at weekend. I observed the engine running for quite a while and noticed that an air pocket exists in the diesel pre filter which sits vertically. ie fuel tank line is connected to the bottom of the filter housing and the other end goes to the electric fuel pump. Its a clear plastic housing with a filter membrane inside but there is a air pocket at the very top of the filter. I guess there should be no air in there?

Thanks
Soulman

I doubt that this is the issue but pre-filters don't cost the earth so changing it would not hurt; at least you will have eliminated one possible cause.

Jeremy

[Soulman]

I just wanted to provide here the resolution that i found to this issue of losing power under load. The issue was in the Injector pump (4 cylinders). One of the plungers in the injector pump was getting stuck so only 3 of the cylinders were getting adequate fuel. Each plunger is activated by a cam shaft in the engine crank case and there is a spring in each of the injector chambers to pull the plunger back down but on one of the injector chambers, the plunger was getting really stuck so it wasn't moving up and down correctly. Probably dirt at some point got into the injector and caused scoring and damage to this particular plunger.

[Jeremy Rowland]

Thanks for letting us all know what the issue was, this can be helpful to future members I am quite surprised at this in one sense but in another perhaps some dirty fuel got through into the injection pump, how did you resolve the issue, I take it that you sent the pump to a specialist pump repair facility?

Jeremy