Fuel Issue

[2stroker79]

Finished my 100 hour service, removed water from my tank. Test run will go after 2700 rpm start d coughing for fuel. Notice during the test run my fuel water separator was not staying full even when I primed it. Any thoughts?

[99yam40]

might help if you posted what motor you are playing with

[2stroker79]

Yamaha 2001 2 stroke 150 hpdi

[99yam40]

model # helps even more,
some times people think they have one thing but it turns out something else.
Model#s do not lie as long as you post the one listed on your motor.

Monitor fuel pressures when problem shows up.
did you drain and flush the fuel system and change/clean all filters and screens

[2stroker79]

Z150TXRZ Model #

[2stroker79]

All filters were replaced in October. Engine was flushed a week ago and checked out fine. Fuel water separate was 3/4 fuel even while priming.

[99yam40]

if they were replaced and then filled up with water and trash, they are no good.

I believe the filter on motor will not stay full while running.
there are screens in the HP pump also

monitor pressures high and medium to see what that are doing, or take to someone that can

[Jason2tpa]

Curious to learn how you know the fuel level inside the fuel/water separator can. Do you have one of those see-through cans?

On the high pressure side of primer bulb, as you squeeze fuel fills spaces of lower pressure first. Keep squeezing the bulb and fuel components down line eventually become pressurized. The first in-line fuel component after the bulb is the fuel/water can. If it's not completely filling, it means air or fuel is leaking out somewhere downline towards the engine.

My guess is since the fuel/water can doesn't fill then your primer bulb doesn't become rock hard? So you keep squeezing and squeezing but the system never pressurizes. Under pressure, fluid and air move to areas of lower pressure. In this case, sounds like the low pressure area is the atmosphere, a.k.a. a leak.

[2stroker79]

Attached is the pic of my brand new fuel water separator just put on. It is all clear with a plastic ring and drain nipple at bottom. This was taken running at 2700 RPMs. It wants to go. At 3600 RPM it coughs and stutters. It does not go limp mode. I tried priming while running but I could feel it pulling fuel but it did not fill up.

[2stroker79]

Yes, while priming the primer bulb did get rock hard.

[Jason2tpa]

Since you're able to pressurize the fuel system prior to ignition, me thinking this is a pump issue. Which one?

Double check all fuel connections for tight fitting. Check that the screw-on top of the fuel/water separator tightly seats to the can. Do the same for the fuel filter.

As mentioned below, you'll need to monitor the fuel pressures to confirm that it is a pump issue, then determine which pump has the problem.