LS170 stalls under forward travel and under load

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CEK

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Apr 8, 2025
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New to this forum, thanks for the assistance.
I have a LS170 with a brand-new rebuilt Shibaura N844T engine. Installed all new components, including OEM injectors, fuel return rail, turbo, filters, water pump, starter. The only original part is the fuel injection pump, but the machine ran prior to the rebuild.

Here's the issue: The machine will start and idle fine and will rev up and run all day but when moving forward at full stick or under load, it stalls out as if it's starved for fuel. The machine will run in reverse without stalling and will maintain rpms if you creep along. I have changed both fuel filters to OEM, checked all lines and injectors for leaks, checked and cleaned the fuel pickup tube, emptied the fuel tank and replaced with fresh fuel, removed the fuel cap, removed the air filters and replaced the electric fuel pump. I have also adjusted the play out of the throttle, but the machine will also stall if you cut the throttle back quickly. Sometimes you can feather the throttle and it will regain rpms without stalling. Again, it seems like the fuel is getting shut off.
Could this be injection pump timing? What am I missing? What else should I check? Any and all help appreciated.
 
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