stumedic
Contributing Member
I posted this on the Yamaha forum but no joy. I really need some help here!
OK, you guys have helped me before with my HPDI so please don't fail me now. My buddy's boat-which is also my tuna boat- all of a sudden developed a problem. The boat is powered by twin 175 HPDI's. The boat ran fine, then the next morning things went downhill with the starboard engine. It started out bogging and rapidly degenerated to barely running. YDIS says engine is fine but the idle is terrible and it stalls if you try to open the throttle. If it doesn't stall it just makes a bellowing noise but doesn't go anywhere. Ran it off a seperate tank, changed the vst filter and the one after it. The vst was spotless. Changed the filter on the engine and the o-ring, changed the low pressure pumps and changed the secret filters on the high pressure pump. New plugs, 4 new injectors and the same thing. started swapping parts from the good engine. Changed the injector drivers, the cpu, coils, plugs with no change. Removed every ground and cleaned and re-installed. I rested my arm on the TPS and the engine started running differently. I adjusted the TPS as per the service bulletin and while I was at it adjusted the throttle butterflys. None of them were sticking. If I adjust the TPS by ear I can get the engine to run. Not perfect but it will make almost 5k rpm's. If you move the TPS a thousandth of an inch in either direction the engine will not run. Swapped the TPS and the o2 sensor from the good engine and it is still the same. I need some help here!
OK, you guys have helped me before with my HPDI so please don't fail me now. My buddy's boat-which is also my tuna boat- all of a sudden developed a problem. The boat is powered by twin 175 HPDI's. The boat ran fine, then the next morning things went downhill with the starboard engine. It started out bogging and rapidly degenerated to barely running. YDIS says engine is fine but the idle is terrible and it stalls if you try to open the throttle. If it doesn't stall it just makes a bellowing noise but doesn't go anywhere. Ran it off a seperate tank, changed the vst filter and the one after it. The vst was spotless. Changed the filter on the engine and the o-ring, changed the low pressure pumps and changed the secret filters on the high pressure pump. New plugs, 4 new injectors and the same thing. started swapping parts from the good engine. Changed the injector drivers, the cpu, coils, plugs with no change. Removed every ground and cleaned and re-installed. I rested my arm on the TPS and the engine started running differently. I adjusted the TPS as per the service bulletin and while I was at it adjusted the throttle butterflys. None of them were sticking. If I adjust the TPS by ear I can get the engine to run. Not perfect but it will make almost 5k rpm's. If you move the TPS a thousandth of an inch in either direction the engine will not run. Swapped the TPS and the o2 sensor from the good engine and it is still the same. I need some help here!