Logo
FULL SITE MENU

250 yamaha misfire and over fueling

Z

zimnucks

Contributing Member
Ive got a 250 hp 2 stroke fuel injected motor , not sure the year as the tag is gone . The engine is only running on 3 cyl and there is a load of fuel coming outta the exh , ive changed plugs , checked spark , removed the VST and checked the needle , pulled the fuel rail and injectors and inspected them , ran the engine with a fuel pressure gauge on and the pressure is constant around 40 . What am i missing any ideas ?
 
Unbolt the fuel pumps from the engine and see if fuel comes out from the pulse port. If there is any trace of fuel replace the pumps. When these pumps fail, they push fuel into the engine and will cancel cylinders. The excess fuel will be visible in the water.

Quick way to tell if you are looking in the right direction, squeeze the fuel primer bulb, if the pumps are leaking the bulb will never really get hard.
 
Back
Top