I have a 68 580ck that this summer I put a new head gasket and 4 new injectors into. It runs pretty good and until now I haven't really noticed any issues. This is my first backhoe. (had to say that in defense of stupid questions) I have used it to dig a few holes and move some stuff around the yard never had an issue. The last couple of times I went out to start it. (trying to keep the battery up it's getting cold up here in Maine) after I let it run for about 20 minutes, I'll rev it up a few times then I put my foot on the throttle and bring the RPMs up to about 1000 or 1200 and move the loader and backhoe to exercise the hydraulics. What I noticed is that the engine wants to stall when I take my foot off the throttle, as it winds down it might stall. Like I said not every time just once and I while. I can hear the engine get very slow and then pick back up. I will say that I have never checked the idle RPMs it doesn't have a Tach. I had an old case mechanic drop by to talk me about how it works and to give me a few pointers, he said it sounded good. That's all I have to go by. I'm a gas engine guy so I'm still learning about the diesel engine. Almost sounds like possibly timing but there is no distributor so am I looking at adjusting the valve lash again? It runs really well and has plenty of power. I'm open for suggestions.
Sounds fuel related. Might be something in the tank that's blocking the suction line or the fuel is partly gelled. There could also be a screen on the fuel line that is partially plugged. When was the fuel filter(s) last changed and do you have winter grade diesel in it? A Case expert will probably have some better info to help you.
I replaced the fuel filters (2) in July when I did the head gasket and injectors. I also drained all the fuel out of the tank and replaced it with fresh fuel. I also put all new seals in the fuel lines when I replaced the injectors.
It still sounds fuel related. Is the fuel shut off not fully opening?
Ok, I have about 1/2 a tank of fuel. Is the only way to check the shut off to remove the line and see how fast the fuel flow is? I did have a problem with the shut off when I tried to shut it off I had a slow drip coming from the center. Once I opened it back up all the way it stopped leaking. I'm thinking I just have to remove the valve and check it?
That would be a good start. If it was dripping may have a slight air leak that could definitely cause problems. Air leaks don't necessarily drip.
OK, did I mention that it ran fine until the outside temperature started to get colder? I'll take a good look at the valve I was also thinking about going over to NAPA and getting an additive to prevent gelling. The other thing I'm going to do is drain the sediment trap at the bottom of the fuel tank and drain the bottom fuel filter and check it for water.
Sounds like a good plan. How cold did it get? Below freezing could gel summer diesel but I'm not thinking that's the problem if it idled for 20 minutes. The fuel should have warmed up in that amount of time. Putting fuel conditioner in doesn't hurt though.
It's been getting into the mid 20's F at night up into the mid 30's during the day. Right now if I went out it will start and idle until it warms up and I can use it. It just wants to stall if I run it at high RMPs for a minute or so and then take my foot off the throttle.
If it was sucking air it might do what you're describing, it would probably also die under full load like if you tried going up a hill in too high a gear and stalled out. Blow back through the fuel line into the tank, and siphon some fuel off the bottom to see how much trash is in there. is there a screen on the pickup in the tank? adding one might help. The other issue could be a sticky/sluggish governor, that MIGHT be helped by running a tank of biodiesel through the machine, but do it in one short time, don't let it sit or you'll be in far worse trouble. I'm assuming this hasn't ever been run all day to burn up a tank of fresh fuel at one shot? at least not by you.
I think there is a screen (strainer) on the fuel tank shut-off valve. The valve would have to be removed to determine that. The leak around the stem of the that valve has a nut with a packing inside it. Slightly tightening it should eliminate any drips.