Engine bogs to steady idle after 20 minutes.

[JimM]

After mowing for 20 min, my zd18 will bog itself down to an idle. If I let it sit for 30 min I'll get another 20 out of it. I replaced fuel filters, air filter, all new oil and hydrolic fluids (including gear box), new battery, removed and cleaned tank, replaced fuses, radiator screen is clear, everything greased, and checked safety switches, also air can be blown through to of gas cap. When it drops down antifreeze temp is 170, trans fluid is 118. Mower Gear box is 115. Any suggestions on something else to try? Fuel pump was 110 degrees and alternator can be heard while running at idle. Not sure if that helps. Will happen on flat or on hills after about same amount of time .
Thanks for any help

 

[JimM]

It currently has 711hrs

 

[Shadow]

Any additives in your fuel? Have seen some instances where an additive will cause the machine to run sluggish after it's up to operating temperature. When it starts to do this, pull the fuel line off that goes into the injection pump and check your flow, make sure its a good strong stream.

 

[North Idaho Wolfman]

I will also add that not treating your fuel can also be a problem with algae growth in some cases.
I treat all my fuel with Soltron (weird name but it works) and Stanadyne, We have huge temp swings and that adds to condensation and algae problem.

 

[JimM]

I put seafoam in with the last tank to try to clean lines. So far hasn't had any effect. I looked at flow through side of fuel filter and level stays the same while running.

 

[JimM]

It seems like an overheating problem, but I can't find anything overheating. If there something that could trigger a fake overheating response from engine?

 

[Blkvoodoo]

Check your fuel cap, see if the vent is plugged by debris, doesn't take much to not let it draw in some cases.

May have to disassemble cap to find anything

 

[rentthis]

Jim, Considering all you have done to correct the problem, I would really like to know the outcome. You blew air through the fuel cap but I wonder if it could still be clogging somehow. Stranger things do happen. Have you tried removing the cap and running the engine?

 

[skeets]

A dumb question, but are there any rubber fuel lines any place? They do get soft after a time, and maybe they have softened up some and are collapsing under load

 

[JimM]

I've unscrewed cap and held slightly above while running and it still has issues. I've also disconnected all fuel lines from injectors and purged any air in lines. I've had two kubota mechanics from different dealers tell me not to bring it to them and to keep trouble shooting myself.

 

[JimM]

The entire fuel line is rubber. Would the fuel line constrict or dialate as it heats up? And if so, I'd imagine it would be after going through hot fuel pump?

 

[skeets]

I have seen fuel lines collapse when they get old and warm,, was just a thought

 

[North Idaho Wolfman]

As I read through this thread one thing keeps popping out, the word gas!
Are you 110% sure it has pure clean diesel in it, as any gas will just mess everything up.
It can also give you the exact issues you are describing.
Open the cap and give a sniff, or better yet drain and dump the fuel and replace it will new fuel!

 

[Shadow]

Change the filters too after you drain and flush the lines

 

[JimM]

The diesel I get I make sure I get from a shell station that constantly had trucks going through it. So they pump a high volume of diesel. But I'll drain tank and replace both filters again.

 

[rentthis]

Jim, sounds to me like you need to be troubleshooting mechanics.

 

[coachgeo]

one thing that can happen....... which happens about same time it hits operating temp. is an air leak. A tiny flap of rubber in old line that opens up when vacuum is high enough. This allows air to egress once the vacuum builds high enough but cause no effect when vacuum is lower.

Get a cheap 12v fuel pump from Auto parts store. Temporary plumb it in as close to tank as you can. This will PUSH fuel instead of it being sucked by the engine's system. Pushed fuel will leak OUT instead of air leaking IN. This could point to your issue by fuel leaks and get you up and running temporary.

If problem exist still then issue is before the pump you just installed.

could it also be a floater (leaf, piece of plastic or) in the tank that gets pulled to the tank outlet? With that in mind..... by pass the tank with temporary installed aux. fuel pump, and fuel filter with some spare fuel lines. Have pump suck fuel out of a Gallon Jug. If problem goes away with this set up; then at least you know it is not the IP or engine's fuel pump. (which is one in the same on a lot of smaller diesels). Then you'll have to reset it up as OEM and start chasing back from IP toward Tank or Visa-Versa to find the problem.

(IP = Injection Pump)

 

[JimM]

I replaced fuel pump, line, and filters... still has the same issue

 

[Grouse Feathers]

I stumbled across this. It sounds like you may have these two solutions already covered, but for what its worth:
http://www.ssbtractor.com/wwwboard/view_all.cgi?bd=kubota&msg=24252

 

[D2Cat]

Hey Jim, what Grouse dug up is the same model tractor as yours. Might vary well be you problem!!