wont run when engined warmed up

[phorton22]

Hey all.
I have been having a issue with this for a little bit now. A little background first.
This machine ran fine, a Bobcat B250, before this and just started, and it runs fine til it warms up or I leave the air blead open.

Anyways:
This machines diagrams do not show a fuel pump, but has a electric fuel pump installed on it, obviously an add on installation.
I replaced all the fuel lines, filter, and the fuel pump as well, even thought the pump was working, it seemed to be at a lower flow, when I replaced it the flow did increase by nearly double.
So this is where my confusion really starts.

After installing/replacing these items was still having the same problems. would run until it was fully warmed up then chug very badly and shut down. Then, after several times of doing this I was suspecting an air leak somewhere. I unscrewed the air blead on top of the filter and air was being pushed out for a bit then diesel would run out. Closed the blead and engine starts and runs fine for a bit and dies, did this several times until I decided to leave the blead open a bit and it ran just fine, I did not run it with a load on the motor but it ran just fine til I shut it off. So 100% positive its a fuel issue.

So it seems to me the the motor is sucking the fuel line dry somehow. but any way you slice it, the pump is not supplying the motor enough fuel - or more acurately, the motor is taking more fuel then the pump is supplying.

Now I also ran the pump and it circulates all the way though and back into the tank so that seems fine.

I next removed the fuel pump. It runs the same. Just fine til warm then will not keep running.

Im not a mechanic, but none of this makes any sense to me.
Help!

Thanks!

 

[Farmeryaz]

Sounds to me the vent on the fuel tank is plugged. A few ideas. One is to open the fuel tank and see if that makes a difference. Or run a fuel line to a diesel can and bypass your fuel tank to see if that makes a difference.

 

[phorton22]

How about just removing the cap? which is what I think you meant. lol

 

[Farmeryaz]

Exactly. I don't know how old the tractor is, but if its not the vent the tank could have something restricting the flow. Which is why by passing the tank would eliminate the tank as the source of the problem.

 

[Leejohn]

Also check for a filter in the tank and the fed line for a pin hole or soft spot, it just might be getting sucked together on the inside. Shouldn't be getting air eather.

 

[john_bud]

It could be as simple as the hose from the tank to the pump has a crack somewhere. I'd replace the entire rubber lines from the tank to the pump. Also inspect the tank outlet to see if there is a crack in the metal. You may also have an object in the fuel tank clogging the outlet. Or the outlet may have a screen that is clogged up with years of gunk.


Then AFTER the fuel filter, run a clear line about 5-6 ft long into a 5 gallon fuel tank. Watch for bubbles. It may take several gallons to get to bubbles, if you do have a defective tank vent. Obviously, you should have a pure solid stream of fuel with no bubbles.

 

[phorton22]

Well I 'think' I got it figured out... I kept going back to the air blead screw on top of the filter. I knew when that was open the pump would pump all day long. Couldnt figure out why when it was open the pump would spit diesel out of it but when I closed it the engine would basically 'drain the line'. Anyways I took a small flat washer and put on the screw and that seemed to solve the problem. Seems the air blead was shutting off the fuel supply. Which I totally dont understand.

 

[phorton22]

Today I was running the machine and had the same problem. Lines are good and tank is fine. Like I referred to earlier, the motor seems to be sucking the lines dry but when I open the bleed screw the pump fills the lines and filter back up and it runs fine again. Anyone have ideas on this?
Thanks.

 

[Don87]

Today I was running the machine and had the same problem. Lines are good and tank is fine. Like I referred to earlier, the motor seems to be sucking the lines dry but when I open the bleed screw the pump fills the lines and filter back up and it runs fine again. Anyone have ideas on this?
Thanks.

Pull the line out of the tank, I think the rubber hose is cracked inside the tank. That's a common problem with the Bobcat Skidsteers.

Or get it running again, and as soon as it shuts down, loosen the fuel cap slowly to see if you hear air rushing in. If it does you are pulling a vacuum due to a bad fuel cap.

 

[phorton22]

It has a solid pick up in the tank which all looks good, no cracks etc. I have tried running it with the fuel cap off so venting is not the issue as well. There is a sensor where the diesel enters the motor. What would that sensor be for?