Engine speed

[Hinomotoman]

Suddenly after about 15 minutes of use, my engine speed drops to idle and then tries to go back up but stays mostly on the low end. Any ideas what may cause this? It's a K3M engine.

 

[mddorange]

Sounds like the old fuel problem. If you are running biodiesel then it could be an algae buildup. It could also be water in the fuel or dirt or air in the fuel lines.

 

[Hinomotoman]

That's what I was thinking but my other four tractors are using the same fuel and run just fine.

 

[thepumpguysc]

Different fuel systems will tolerate water & dirt better than others.. so saying THAT doesn't "hold water" so to speak..
Change the filters & "back-blow" the fuel line coming from the tank & be done.
I'm working on an inj. pump right now that the customer said the EXACT SAME THING.. I cracked it open & the entire pump was full of rust..
Some filtration systems are better than others & some inj. systems are more tolerable than others..

 

[PILOON]

As said, back blow as there might just be crud blocking the tank screen.

Also you might simply disconnect the fuel line and see what kind of flow you'll get, bet it is minimal. (then back blow)

On TBN I read a cool trick to vacuum clean out that tank crud----you hook up a vacuum source with a container in the suction line in such a way that the crud gets deposited B4 it can be ingested by the vacuum pump.
But first ask the wife if OK to use her vacuum. LOL

 

[Hinomotoman]

I changed the filter and the fuel looked good. Started it up and again it ran normal for about 15 minutes and then started to bog. I will back blow the fuel lines and see what happens. Thanks for the suggestions.

 

[Hinomotoman]

Here's what I found. No blockage in fuel system from tank to top of injectors. When I bled the system, the RPMs dropped drastically on the first two injectors. It didn't on the back one. I took the injector out and the tip was covered with dry black smut. Now I understand how this will make it run on two cylinders. I don't understand why it would wait for 15 minutes to do it. Any comments?

 

[thepumpguysc]

The engine got warm, metal starts to expand..
You either have a problem w/ that injector.. a problem w/ the inj. pump OR & its a biggie..you have an engine cylinder going down.
DONT just get 1 injector!!! have them ALL checked..

 

[GrocMax]

Is this a gravity feed fuel system?

Check the vent on the filler cap.

 

[thepumpguysc]

IF it was DRY.. it means no fuel is being injected into or thru the injector..
I suspect the injection pump.. you say the "back cylinder".. so it will be easy to remove the steel line ON THE PUMP to SEE if fuel is coming out of it..
Do yourself a BIG FAVOR & use the double wrench method.. hold the pump "nut" while loosening the line nut.. or you stand a chance in loosening the pump [delivery valve holder] nut before the line comes loose..[not good]
You can do the same for another cylinder ON THE PUMP to compare the fuel delivery. [squirts]