D722 using more fuel than supplied

[Jshearer]

Hello, I have a Grasshopper zero turn with D722 that started running out of fuel in the filter between the lift and injection pump and of course would stall or die at that point. I replaced the lift pump with a factory replacement with no help. I then installed a low pressure electric, also no help. What I did notice was when the electric pump was turned on it started sending fuel through the return to the tank before the motor was started. The return comes off the front injector. I went back to the mechanical lift pump, restricted the flow of the return and had no more problems, filter stays full. Seems it's bypassing too much fuel ? Why ? Thanks in advance !

 

[North Idaho Wolfman]

Hello, I have a Grasshopper zero turn with D722 that started running out of fuel in the filter between the lift and injection pump and of course would stall or die at that point. I replaced the lift pump with a factory replacement with no help. I then installed a low pressure electric, also no help. What I did notice was when the electric pump was turned on it started sending fuel through the return to the tank before the motor was started. The return comes off the front injector. I went back to the mechanical lift pump, restricted the flow of the return and had no more problems, filter stays full. Seems it's bypassing too much fuel ? Why ? Thanks in advance !

That port that comes off the top of the injection pump is a free flow, there should be no restriction at all in that line, it's job is to burp air out of the Injection pump.

Adding an electric pump was just forcing fuel into the injection pump and back out of it, lucky for you it had that feature as if you did that with an older pump you would have just plow the seals out of the pump and dumped fuel into the oil.

Now to get to the issue, first bottle (gravity feed) the injection pump and see if that works if it runs fine on that then your issue is before it, could be a restriction (junk) in either the inlet or outlet of the fuel filter or the fuel tank, or it could be the vent to the fuel tank is plugged.

 

[Jshearer]

Thanks North Idaho Wolfman, I should have gave more info. I cleaned the output from tank, all new hoses, both filters, made sure tank was clean and full and lastly new mechanical pump. Fuel shut off seems to be opening as it should.
The return line that I restricted (not close) is plastic and clamped with spring clips, not sure how much pressure it could hold. This tube came off the front injector from a side fitting. Not sure of the port you're referring to on the injector pump but I'll look.
Also, when I manually filled the filter it ran well until the filter ran low then stalled or died. This usually took about 15 minutes +/- of no load run time.

 

[200mph]

If the filter bowl does not remain full it seems there is a restriction between the fuel filter outlet and the tank.

People have found blockage within the filter housing and it's not uncommon to have foreign matter in the tank or bacteria growing that will impede fuel flow. I'd pull the hose at the fuel filter and make certain fuel flows at a good pace into a clean preferably white bucket. Let the entire contents drain and look at what comes out. Also watch if the fuel rate varies.

 

[Jshearer]

I'll go back through and check for obstruction. Thanks

 

[North Idaho Wolfman]

If you find nothing in the fuel or tank outlet (look for slime or black speckles, that's algae), A non venting tank will also cause the fuel not to flow to the fiter, run it with the fuel cap cracked open and see if the issue disappears.