Anything else to do when changing a head gasket?

[mikehaugen]

I wonder if that can cause the tractor to run lean. Seems like it stalls either because its too lean or sucking air. Can running lean . It run hot?

I would think so, but I'm not sure how lean a diesel will actually run?

 

[Topher265]

...snip... so I traced the fuel lines back to the tank. Found the fuel pump and, lo and behold, there was another inline filter between the tank and the fuel pump. But of course there would be. Just makes good sense. I bet he's clogged up. But I think I'm gonna get some line and bypass him just to make sure. Then I can get everything in one order.

Thoughts?

It sounds like you found a very likely cause.

I wonder if that can cause the tractor to run lean. Seems like it stalls either because its too lean or sucking air. Can running lean . It run hot?

Yes, running lean increases temperatures in the combustion chamber. This is compounded in this situation because the cooling system capacity is rather small (2 quarts!?) so it's hard for the system to get rid of excess heat. This is why it is possible to damage pistons if running super lean... the heat can actually melt pistons or parts of them.

I would think so, but I'm not sure how lean a diesel will actually run?

Diesels run leaner than gassers to begin with, sometimes as lean as 120:1 (air:fuel) in the right circumstance on the right engine (that lean it would be at idle). Technically, gasoline engines have the most complete burn at 14.6-14.7:1. Yet max power from a gasser is on average between 12.0-13.5:1. Gasoline engines have come a mighty long way once you look at a Gasoline Direct Injection (GDI) engine in terms of how lean they can run. A carb'd engine might get away with 15:1, where a GDI can do around 60:1.

 

[mikehaugen]

Diesels run leaner than gassers to begin with, sometimes as lean as 120:1 (air:fuel) in the right circumstance on the right engine (that lean it would be at idle). Technically, gasoline engines have the most complete burn at 14.6-14.7:1. Yet max power from a gasser is on average between 12.0-13.5:1. Gasoline engines have come a mighty long way once you look at a Gasoline Direct Injection (GDI) engine in terms of how lean they can run. A carb'd engine might get away with 15:1, where a GDI can do around 60:1.

I guess what I was asking was more along the lines of how lean (relative to "optimum" mixture for given fuel) will a diesel run? My thinking is that a gas engine is more forgiving, but it's just an assumption.

 

[Lobanz]

Here's Mr Kubota's weak stream from the fuel pump.

 

[Coyote machine]

Too lean, sucking air = not enough fuel: runs hot, boils coolant, etc. So YES!

 

[Topher265]

Here's Mr Kubota's weak stream from the fuel pump.

Wow.

That's awful. I imagine bypassing that filter will solve your problems. It's barely getting fuel at all.

 

[Lobanz]

Wow.

That's awful. I imagine bypassing that filter will solve your problems. It's barely getting fuel at all.

Actually the dealer had one in stock, so I will just change it. Will see about cleaning out tank while I'm at it, but doesn't look bad poking a flashlight in it. Will have to empty it anyway. Got a little extra fuel line at the dealer in case I have to replace some. I wonder if that restriction would kill the lift pump. We'll see.

 

[Topher265]

Actually the dealer had one in stock, so I will just change it. Will see about cleaning out tank while I'm at it, but doesn't look bad poking a flashlight in it. Will have to empty it anyway. Got a little extra fuel line at the dealer in case I have to replace some. I wonder if that restriction would kill the lift pump. We'll see.

Excellent. Lots of restriction would make life harder on the lift pump, so I would think overall it's life may be shorter but you may be luck enough that it lives for a while longer .

 

[Lobanz]

Wahoo!

It was the hidden rear inline fuel filter. Man was it dirty back there. Piles of dirt on the floor now. Took it all apart and cleaned everything. Took gas tank completely off and cleaned it. I could not even blow through the old filter. Replaced it and flow is very good. The little lift pump will spray diesel several feet out of the loosened banjo fitting on the injector pump. Mowed quite a bit with my flashlight in my mouth. Didn't bog down at all in high dew covered grass with dull blades. The only time it struggled at all was if the mower deck could not discharged the grass fast enough and it clogged a little. Changing fuel filter may have helped the temp a little, but not much ( I've read that diesels actually wont run hot if run too lean -- they just won't run at all). But it did not overheat or anything. No coolant loss. The temp meter still reads higher than I like but it plateaus off at a point and stabilizes there just a little below the hot white line. I think the temp sensor is just reading a bit high. Need more load testing to see how it behaves now that its fuel system is back to normal. Hopefully just a few more little things and Mr Kubota can be discharged from the hospital.

 

[Coyote machine]

Xcellent! Now you're beginning to see the big picture. Clogged primary fuel filter causing lack of fuel delivery to lift pump/IP and injectors, of which all suffered in one way or another. Lean fuel delivery causing overheating when tractor being worked hard with dull bladed mower and high grass, etc.
How tractor ran at all is beyond understanding, but I'd bet you were saving big time on fuel use!