Fuel issue?

[PatMcD]

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]

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

 

[PatMcD]

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]

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]

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]

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]

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]

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

 

[CCWKen]

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.

 

[PatMcD]

Any electrical reason why it would limit rpms? I notice my fuel gauge reads near empty unless it's full. Bad water sensor on the filter?

 

[PatMcD]

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.

I'll see if I can find that.

 

[davesl708]

Any electrical reason why it would limit rpms? I notice my fuel gauge reads near empty unless it's full. Bad water sensor on the filter?

Not likely electrical.
With the rpm problem and the fuel gauge sticking how old is the fuel? Are you getting fresh fuel or is it from a storage tank. Could be algae growing and clogging.
Look for a second filter. My diesel has one near the fuel pump and one near the tank outlet.
Also, clean the cap vent. Could be a critter built a nest in the vent hole or other debris is plugging it.

 

[PatMcD]

This is the pump. Zexel.


This is a diagram of the fuel flow. The only filter I see is the main one. No screen in the tank. There is no fuel shut-off because the tank is lower than the filter and pump. I'm not at all familiar with injector pumps, so I don't know if there is an inlet screen or something on it somewhere.

 

[PILOON]

"No screen in the tank. There is no fuel shut-off because the tank is lower than the filter and pump. I'm not at all familiar with injector pumps, so I don't know if there is an inlet screen or something on it somewhere."

tank is lower than the filter and pump,--- odd as that suggests a lift pump would be needed as gravity is not there to supply the injector pump.
That being the case priming must be a *****.
OK, so the injector might draw but all the lines need to be ABSOLUTELY tight as the slightest air leak will cause problems. Even an old rubber line might let air seep in.
Typically injector pumps can not handle air. (that is why we need to bleed all lines to prime a system)

 

[Halftrack]

If the problem gets worse as the engine warms up, I would consider the diesel fuel is contaminated with gasoline. Before you spend a lot of money on parts, I would drain the tank and replace the fuel with clean fresh diesel from a reliable source. Drain some of the fuel into a flat pan and you should be able to smell the gasoline vapors evaporating from the diesel.

 

[PILOON]

Just looked at the pix U posted.
That red line I see is not fuel line material, it is air or welding hose.
I bet fuel has deteriorated the hose to the point that it weeps or has swelled causing blockage.
Start by replacing any non standard hoses with proper fuel line material.

 

[PatMcD]

I *might* have found the problem. Last night I found a schematic online for the Zexel pump. It showed a screen at the inlet line. Pulled it this morning. It was pretty well clogged: almost to the point of not being able to see light through it. I blew it out with air (hold tighter next time so I don't lose it across the barn floor!). Reinstalled it, tightened things up, purged the air, and started it up again. Way higher RPM! No surging or "missing". I'll have to go mow a field or something to see if this truly fixed it or not. Keeping my fingers crossed.


Here's a pic inside the bottom of the old fuel filter I took off. Pretty ugly.


Now, as to the red fuel line: that's how it came from the factory. I don't know. If it has deteriorated inside, maybe that's why that small screen was clogged instead of that stuff being caught by the filter? I'll get a new piece today.

 

[davesl708]

Glad you're getting it nailed down. Looks like some water has been in the filter too. Maybe use a Mr Funnel or Racor filter to pre-filter the fuel to avoid the problem again.

 

[PatMcD]

I just got in from running it hard for a few hours. She's all good now.
So, clogged inlet screen in the pump body caused by crappy fuel.
Thank you all for the help!

 

[ozley]

I just got in from running it hard for a few hours. She's all good now. So, clogged inlet screen in the pump body caused by crappy fuel. Thank you all for the help!

I glad you found that screen and got it running. I got my 5030 in the spring of 2011. Have had no trouble but glad to know what you found.