Fuel Starvation mid/high range under load

[FishinFrantz]

Having fuel starvation issues on a 2002 F225 TXRA. I have replaced the racor filter,10 micon fuel filter, and vst filter. Without a load I can easily run up to 5k RPM but out on the water motor will bog from 5k down to 3200. I did notice that power resumes once I give the primer ball 5-8 times power is restored for another few minutes. Any advice would be greatly appreciated.

[fairdeal]

So if you can ameliorate the problem with the primer bulb, that means your lift pump is not keeping the vst full.
Have you checked / replaced the pressure regulating valve
(It's zip tied to the lift pump)
If that is ok - check for a restriction - or an air leak - before the lift pump

[FishinFrantz]

I have not replaced the checked/replaced the pressure regulating valve. I will have to check it out to see if it is functioning and will check for an air leak. Thank you for the advise.

[FishinFrantz]

I checked the pressure regulating valve on the low pressure fuel pump and that was operating correctly. Purge the fuel lines and verified good seals on all. I did find that the check valve going from the VSF to intake silencers is not opening. Could this cause an over pressure in the VSF and not allow fuel to flow properly?

[fairdeal]

I checked the pressure regulating valve on the low pressure fuel pump and that was operating correctly.

ok - understand, it needs to be closed until the pressure on it begins to exceed 10 psi - otherwise the lift pump just pumps in a circle rather than fill the VST



I did find that the check valve going from the VSF to intake silencers is not opening. Could this cause an over pressure in the VSF and not allow fuel to flow properly?

I don't think so - you said you are able to fill it with the primer bulb when it dies from 5k rpms -
up to that point the lift pump should have been continuously running -
with pressure of 10-15 psi -
seems it should be able to replace the fuel that is being used, even if the VST is not vented

assuming the lift pump is running when it should be,
something is preventing it from "keeping up" at 5k rpms.

I would test the pump - engine doesn't have to be running,
you can use test lead to make the pump run with just key on

put a vacuum gauge on the suction side - see what you have - should be virtually nothing


an air leak on the suction side can be visualized by patching in a piece of clear tubing - you'll see the pump pulling bubbles through it

put a pressure gauge up by the VST inlet/f-shaped filter - make sure you've got 10-15 psi

[FishinFrantz]

Replaced fuel all fuel lines to Racor filter assembly to the Low Pressure Pump. Replaced check valve at the air silencer and everything checked out good. Did lake trials for 4 hours and never once did she starve for fuel.