Bad fuel aftermath

[dodge man]

I'll throw out an idea, there is a small fuel pump towards the back of the tractor. It has just enough power to deliver the fuel to the main injection pump. Its a little silver thing, and it looks just like a fuel filter in terms of size and shape. They can go bad, and the main pump will often still pick up enough fuel to keep it running, but not well. If you turn the key on, but don't start it, you should be able to hear it running, kind of a clicking-pumping sound. If you don't hear it running, it needs replaced or the wiring needs fixed.

 

[kuboman]

I'll throw out an idea, there is a small fuel pump towards the back of the tractor. It has just enough power to deliver the fuel to the main injection pump. Its a little silver thing, and it looks just like a fuel filter in terms of size and shape. They can go bad, and the main pump will often still pick up enough fuel to keep it running, but not well. If you turn the key on, but don't start it, you should be able to hear it running, kind of a clicking-pumping sound. If you don't hear it running, it needs replaced or the wiring needs fixed.

I've had these pumps make noise and even deliver fuel to the point of thinking it was alright but in the end when the engine was running it would either quite or not deliver enough fuel. Moral of the story...even when it sounds like it is working it may not be.

 

[Chilly807]

So it's an inline 12volt boost pump? Interesting, those are often either part of the main pump or have a cam-driven lift pump. There may be a separate fuse for it as well, but if it runs for 20 minutes and then dies out it's probably not the fuse.

It's too bad there isn't a fuel pressure gauge between the injection pump inlet and the boost pump. Usually they need 10-20 psi to work properly, although they will operate with as little as 5 psi.

One other thing to look for is a kinked hose or pipe between the fuel tank and the injection pump, probably before the fuel gets to the boost pump. If there is a restriction in that line, it's possible for the boost pump to cavitate and put air in the injection pump over time, which will cause the engine to die out.

Ideally, one should remove the fuel line before it gets to the boost pump to check for unrestricted flow. I don't say it should spray fuel everywhere, but there should be a free flow from that line under gravity pressure. The filter will restrict it slightly, but not enough to starve the pump.

One thing we haven't mentioned is a restricted air vent. As the tractor uses fuel, air enters the tank to replace it, otherwise you'll have a vacuum in the fuel tank which won't allow any more fuel to flow to the pump. You said there was a leak in the top of the tank, so that might allow enough air in to vent the tank, but again it might not. Running under load for about 20 minutes then dying out sounds like the tank isn't venting properly. I've seen people put a plastic bag under the fuel cap to try and stop a leak. Result is no vent = no run after a bit.

To check the vent, it can get messy. One way is to fill the tank as much as possible, replace the cap as normal, then remove the fuel hose either before or after the filter. I'd recommend before the filter, since that way you remove the filter from the equation. Let the whole tank drain back into your fuel jug (it should be big enough to contain whatever is in the tank) If you get good flow for the first couple of minutes, then it peters out to barely a trickle (or acts like an air-locked pop bottle), then you have a vent issue. Remove the fuel tank cap and it should flow freely again. I think Kubota uses a vent device in the fuel cap itself, so if that's what's wrong, replacing the fuel cap is relatively cheap and easy. You will most likely have to bleed air from the fuel system when you're done checking this.

Some folk say to run the engine until it starts to die off, then loosen the fuel cap and the engine should pick up if the vent is the problem. That works better with a gas engine than a diesel, since there is often air entrained in the fuel flow if the pump is starving, so the engine may either not recover before stopping or takes a few minutes to clear the air.

Apparently some of the Kubota filters have a shut-off feature, that cuts off fuel flow when the filter bowl is removed. Mine is supposed to have it, but I haven't changed the filter yet so I can't say for sure. There might be a problem with that as well.

According to the manual I have... "When the fuel filter bowl has been removed, fuel stops flowing from the tank. If the fuel tank is almost full, however, the fuel will flow back from the fuel return pipe to the fuel filter. Before checking, make sure the fuel tank is less than half-full."

They recommend cleaning the old filter in kerosene, which I don't agree with. If the filter is dirty, replace it in my opinion. Less chance of contaminating the fuel system with dirt washed out of the filter.

From what you've told us, I think that fuel starvation is the problem, but the cause of it leaves a few choices yet.

Sean

 

[farmgirlky]

Interestingly, yesterday afternoon I tried mowing again. I mowed my front yard, which is flat, and it did pretty well. Then I went out back to see how it did on inclines. It definitely struggled to get up a moderate incline with the mower going. But it didn't die. Then I took it up to the pasture which not only has some pretty serious hills but also is quite overgrown. In past years my mower had no problem with either the hills or the weeds. The tractor did pretty well back there yesterday, but it continued to lose power when it had to go up OR DOWN hills. But I mowed for almost two hours, so it was definitely better. I will try some of the diagnostics mentioned before to try to get it back to the way it was before all of this. I've looked for kinks in the gas line, and I'll try to check the fuel pump and the gas cap (you're referring to the cap I take off to add diesel, correct?). Thanks everyone--you've been extremely helpful. It's great to have this resource.

 

[DiezNutz]

One thing we haven't mentioned is a restricted air vent. As the tractor uses fuel, air enters the tank to replace it, otherwise you'll have a vacuum in the fuel tank which won't allow any more fuel to flow to the pump. You said there was a leak in the top of the tank, so that might allow enough air in to vent the tank, but again it might not. Running under load for about 20 minutes then dying out sounds like the tank isn't venting properly. I've seen people put a plastic bag under the fuel cap to try and stop a leak. Result is no vent = no run after a bit.
{snip}
I think Kubota uses a vent device in the fuel cap itself, so if that's what's wrong, replacing the fuel cap is relatively cheap and easy...

Great post Sean, you beat me to the part about the fuel cap & tank venting - exactly what I was thinking, but you went into lots more detail. :thumbsup:
The only part I wasn't really sure about is whether this tractor has a vented cap. But I have definitely seen this happen on gas lawnmowers, when the cap vent gets clogged up with debris. Worth checking, anyway.

 

[Chilly807]

Unless there's a separate vent hose, the cap has to be vented. You can try leaving it loose deliberately when you start mowing and see what happens. Keep an eye on it though, they have been known to vibrate loose and fall off, directly under the mower. Well, if it did that and you had to put a new one on, it would rule out the fuel cap anyway...

From what you've said, the situation is varying a little bit from day to day. There could be debris in the tank, it's happened before. Cleaning that out means taking the tank off, which isn't a little job.

Sean

 

[EE_Bota]

I have a BX2200.
It does have a vent in the cap.
It does not have a fuel bowl.
It often does have a fuel leak in the top of the tank, and it is the side opposite the filler cap. It is where the fuel level sending unit is. It is likely that this will let in air if need be.

I can plainly hear my fuel pump run as soon as I turn on the key, and the engine is not yet running. If need be, you may have to kneel beside the left side of the tractor, and listen (just in front of the rear wheel, and at about the level of the top of the mower deck.) Please be very sure the tractor is not running, and the brakes are locked, and there is no chance of getting hurt. It is a pretty fast clicking sound, like wind-up teeth chattering. Once you hear the pump, you will know what it sounds like, so you are likely to hear it much more easily in the future.

I will monitor the thread, and report the exact fuel pressure when I get home in a couple of hours.

 

[EE_Bota]

Looking in my manual for the electric fuel pump pressure reminded me that I could not find it last time either. So, what I did then was look at a variety of replacement fuel pumps to find their pressures. The majority of that type seem to run 6psi. With no major obstructions such as clogged fuel filters, etc, 6psi should be more than sufficient.

 

[farmgirlky]

Well, I mowed in my pasture yesterday, and the tractor did very well. It died twice on me, but when I restarted the tractor it went back to full power instead of peetering out like it was before. I think maybe it just needed time for the good diesel to work its way through the system. But I'm still going to investigate the fuel pump thing. Thanks EE_Bota, and I promise not to stick my head under the mower with it turned on. Thanks everyone for your help. This is a great resource.

 

[EE_Bota]

Well, I mowed in my pasture yesterday, and the tractor did very well. It died twice on me, but when I restarted the tractor it went back to full power instead of peetering out like it was before. I think maybe it just needed time for the good diesel to work its way through the system. But I'm still going to investigate the fuel pump thing. Thanks EE_Bota, and I promise not to stick my head under the mower with it turned on. Thanks everyone for your help. This is a great resource.

That's good to know.
But many are injured as the tractor rolls over them or pins them against something. So I gather that the most safe place to be is in the seat buckled in, or well away from the tractor altogether.

Many people who suggest something to try will also include a safety reminder. It is not related to what we think the other person knows, but more due to the stories we all read of people being injured needlessly because of not following even the most elementary of safety precautions one particular day, often when they had always followed them in the past.

It has been less than a year that I read about a man hit by his own bushhog, but whether he promised not be hit before he left the house is unknown. I tell our maintenance force as often as I think to: "Remember, nobody begins a job thinking they will be injured, yet many are injured...."

 

[KWentling]

For those that have a leaking tank, my dealer repaired the fuel gage leak under warranty, but that turned out not to be my leak. Turned out there are screw in fittings with hoses on the back corners of the tank that were leaking. I removed them and used teflon tape on the threads and cured my leak. Also discovered that the same fuse for the fuel pump feeds the tail lights, so no tail lights, no fuel pump. (dealer pinched the tail light wiring) You should be able to hear the pump run sitting in the seat with the key on but engine not running. If your still having fuel problems, I would cut open an old filter and see if you have the black slime indicative of an algae problem. Depending on the severity, a few more fuel filter changes might cure it or a good tank cleaning might be needed. If no slime I would look at the fuel pump.

Kim

 

[Lockport]

I have had a similar problem a couple times until one day when it started dying I opened the hood and noticed erratic behaviour of the solenoid. I saw it cut in and out causing the engine to nearly quit.