Fuel starvation mystery

[Good Sport]

Symptoms:

After enging is warm, it develops a high-pitched whine at low speed. Sometimes whine volume increases, and is accompanied by "stuttering" and/or speed drop-off. Occasionally, boat stalls on power-up hole shot.

Engine:

1998 Volvo-Penta 5.0 G.I.
Model #3858913

What we've done:

New low and high pressure fuel pumps.

Replace resorvoir for HP fuel pump.

Replace throttle body.

Pressure and vaccuum test fuel lines and filters.

Checked fuel pick-up tube, backcheck valve and fuel lines.

I have a lot of confidence in my mechanic. He works on Volvo-Penta only with many years of experience. He has discussed my issues with the factory reps and others. It's a major mystery to all.

Anybody that can provide the answer will "stump the stars"

 

[Don S]

Re: Fuel starvation mystery

The whine of the pump will increase when the pump is getting air in it.
I would put in a section of clear hose between the engine fuel filter and the fuel hose and run the boat under load and look for air bubbles.
Also check the fuel tank vent hose. If it is plugged or partially plugged, it would cause your problem. Even a low spot in the hose that traps gas in the hose could cause a restriction to fuel flow.

 

[Good Sport]

Re: Fuel starvation mystery

Don,

While the engine was whining, I removed the gas cap to insure full ventalation. Whining continued. Your idea about a clear fuel line sounds like a good one. Thanks!