John Deere F935 w/ Yanmar engine

[Dennisinmo]

I'm posting here because my church's JD F935 has a 3 cylinder Yanmar diesel engine with 1930 hours. Problem: When the motor warms up, the motor will lose power, not being able to run up hills or engage the blades. I've replaced the air filters, fuel filter, new fuel pump, new fuel hoses. I'm now wondering if I have scored cylinders or bad head gasket. Doesn't seem to smoke excessivly. Any checks I can do at home to verify the problems?
Thanks
Specs: 3 cylinder Yanmar diesel model no. 3TNA72UJF 22 HP

 

[fixitmandean]

We had the exact issue with ours. We have a mower, brush and a snow blower that I customized to fit this winter. It slowly lost power this fall. We discovered that the injectors were not atomizing the fuel and not letting enough fuel in to the engine. We had them rebuilt and now it has good power.

 

[normde2001]

Try removing the exhaust manifold and running. It could be plugged causing your problem, or you can actually see each cylinder firing, and tell if 1 or more is not right.

 

[zzvyb6]

I had a problem with the fuel pickup hoses in the fuel tanks. They turn to hard brittle material and had air leaks. Changed hoses and now have full power. You have to remove the tank(s) to repair them. Basically the fuel pump was sucking air.

 

[pmsmechanic]

Thank you zzvyb6!! I've been having air in fuel problems with my F935 for a few years and never realized there was a rubber line in the tank. Of course the issue goes away if the tank is full but slowly becomes a problem as the fuel level drops. I will check this out. No, I won't waste my time. I'll just replace the lines and be done with it. Once again thanks.