View Full Version : Fuel Problem Mercruiser Scorpion 330HP

06-24-2010, 11:55 PM
Any help is greatly appreciated on this.....I'm going crazy here trying to figure this out.

After a few minutes running time in my boat, if I shut down the engine for a few minutes, I can start it right up and about 30 seconds later the engine shuts down as if it is running out of fuel. Fuel pump has been changed. Found microscopic hole in the fuel line from the tank and replaced the whole line from the tank to the filter/water separator. The fuel travels from the filter to the pump and then through a "fuel cool" system prior to going to the fuel rail via insulated high pressure line.

When the problem occurs, I can remove the schrader valve at the fuel rail and purge an air/fuel mixture out of the rail by running the fuel pump and connecting a hose into a spare fuel can. Once the line is purged of all the air, the engine starts right up.

Another symptom that may be associated with the problem is that during idling after a ski run, the idle speed runs at 2500 to 3000 rpm. I believe this is a result of a lean fuel mixture created by air introduction into the fuel rail.

I have checked/replaced all the suction fuel lines to the fuel pump and cannot find anything that would cause air. My best guess is that the filter being so close to the engine is allowing the fuel to heat up and the combination of the negative pressure in the suction line and the preheated fuel is causing the fuel to boil prematurely and causing the pump to cavitate further compounding the problem.

If anyone has had any dealings with this combination of fuel cool and "oil filter" style fuel filter/water separator, please respond.

Thanks in advance.

07-01-2010, 12:18 AM
Good news!!!
I found my problem.......
The Gekko I own has a fuel tank with a check valve in the hose barb at the tank. The valve has a negative 3lb pull force to enable fuel flow (Ifanyone can tell me why....please elaborate....). The tank has a 12+ foot distance (fuel hose) to the fuel filter and another 3ft to the suction side of the electric fuel pump. This fact coupled with the heat produced by the engine and atmosphere in Florida created a combination that allowed the fuel in the line just prior to the fuel pump to boil and create fuel vapor. Upon startup, the fuel pump would pump enough vapor/fuel mixture to allow the engine to run for a few moments and then stall. I removed the tank check valve and all is well now. Hope this thread helps someone in the future. I sure have gained knowledge from this site in the past and hope to pass it forward.