have a 4010 fuel injected on site, 61hours, had its 50 hour done recently. when you throttle up the engine will wind to a certain point, then sort of die, loose power and RPMS, making a sort of 'sucking' sound, then kick back in, rev up, jerk sputter, die down again. . . .
sort of like its choking or starving
all dealers in area booked for 4-5 weeks and we need this on our job site.
I did open fuel line where it connects to cast fuel block, cranked it over, slow fuel stream. Should gas be shooting out of that hose?
How do I check fuel pump output - on a job site, with just hand tools

I could try to get a video and post it if that'd help

 

Loosen the fuel line at the injector and crank it and you should get a forceful spray which would indicate good fuel pressure. If not, check the fuel line and any filter for restrictions. If those are clear it may very well be the fuel pump. I recently bought a 2007 310 mule--carburetor-- and the PO said that he had replaced the fuel pump 3 times. It has about 640 hours.