Yamaha 150hp 2-stroke low fuel pressure

[tcanna]

I have a 2000150hp fuel injected 2 stroke (SX150TXRY) that is getting low fuel pressure, almost no fuel pressure 5psi, out of the VST. My question is should I start with the diaphragm lift pumps or take apart the VST. Also curious if bad injectors would cause low fuel pressure out of the VST?

 

[99yam40]

I would check to see if VST gets filled up with fuel and if the pump in the VST runs

 

[tcanna]

I would check to see if VST gets filled up with fuel and if the pump in the VST runs

If its filling up that would indicate the lift pumps at good correct?

 

[99yam40]

yes
also ,the pump in the VST gets its lubrication and cooling from the fuel it pumps.
if no fuel , it can harm the pump

 

[tcanna]

yes
also ,the pump in the VST gets its lubrication and cooling from the fuel it pumps.
if no fuel , it can harm the pump

Good to know, that’s most likely what happened because I know one of the lift pumps was recently replaced. Where can I crack open the VST to ensure it is filling up?

 

[boscoe99]

The VST has a drain fitting. Open the drain. Pump the primer bulb. Fuel should flow from the drain.

After ensuring the VST is full of fuel, you can apply battery positive and negative directly to the wires to the high pressure fuel pump. You should then have rated fuel pressure. If not, either the pump or the pressure regulator (maybe both) could be at fault.