Fuel issue?

PatMcD · Sep 13, 2016

My U5030 (310 hrs) has been running odd. Starts up no problem and runs fine for a while. When it gets warm, after a 1/2 hour or so, the rpm's are limited to about 1500-1700 or so. Won't rev beyond that. Let it sit for 20 minutes or so, and I can go back to 2000 (which is about where I run it for bush hogging). Few minutes later, it's back down to 15-1700.
Changed the fuel filter (there was a little water in the bottom of it, along with some rusty looking residue), air filters are clean. Just did all my 300hr maintenance. Problem occurred before and since that.

Just experimented on a cold engine to see how high the rpm's would go. She will wind right up to almost 2700, BUT it runs very rough, almost like it's skipping, and when it "skips", it puffs white smoke.

Injector bad? Did the water I drained off the fuel filter muck things up?

davesl708 · Sep 13, 2016

White smoke indicates water. Are you loosing coolant?
Might try some fuel additive to get rid of water and clean the fuel system.

PatMcD · Sep 13, 2016

Another question, and probably related: should my fuel tank be under negative pressure? I just loosened the cap and she wooshed in air. Is the vent the little tit on the side of the fillee spout? Is got a solid rubber cap hose clamped over it.

ozley · Sep 13, 2016

PatMcD said:
Another question, and probably related: should my fuel tank be under negative pressure? I just loosened the cap and she wooshed in air. Is the vent the little tit on the side of the fillee spout? Is got a solid rubber cap hose clamped over it.

No the cap should have a working vent. Try running with the cap off next time it will not build RPM's.

PatMcD · Sep 13, 2016

I somewhat cleaned the tank and the lines to the filter and from filter to injector pump are clear. I start it up and give it max throttle (2600rpm) and let it sit there and it slowly goes down. can't maintain the high rpm. settles down to 1500 or so.
Doesn't matter if the fuel cap is off or not.

PILOON · Sep 13, 2016

Sounds like starvation.
Could well be some crap clogging the screen where the fuel line leaves the tank.
Try disconnecting the fuel line just B4 the filter and blowing air backwards into the tank.
That would clear any crap away from the screen thus proving if that is your problem.

Were it a bit of water it would sort of stumble and sputter but keep running once the water passed.

You did say 'wooshed' when cap was removed. That should not be as air needs to get in otherwise you have negative pressure.
Indicates vent in the cap is plugged.

George2615 · Sep 13, 2016

Does your 5030 only have one fuel filter? I have a different model tractor but have 2 filters. There may be a pre filter on yours that needs to be replaced.

PatMcD · Sep 14, 2016

Only the one filter. No screen pick up in the tank.

CCWKen · Sep 14, 2016

I've seen reports that corrosion in the injector pump return check valve will cause the governor to lower rpm. If you had water in the fuel, It's good bet the check valve is sticking. I don't know your tractor but check if there's an injector return line to the pump as well as a return to the tank. A few pictures of the setup might help. If you can't get access to the check valve, the injector pump will most likely need rebuilt.

Also; if you have a tank shutoff valve, it's more common than not that there's a screen on the fitting that goes into the tank.