Fuel Starvation

[billo001]

I have a 4.3 liter OMC in an 18ft Sunbird. When first starting the engine will run and then stop. First though was that the fuel pump wasn't working so I replaced the relay that powers the fuel pump. Removed the fuel filter and filled with fuel and the engine ran great. Same thing happened a week later. Removed the fuel filter filled with fuel and the engine ran great until a week later. It seems that the relay will not allow the fuel pump to start until the engine has started. It almost seems as though the fuel pump its loosing its prime. Do I need to replace the fuel pump or should I remove the relay and wire direct to fuel pump so the it starts to pump as soon as ignition is turned on. Thank for the help in advance.

 

[DP]

Re: Fuel Starvation

Not knowing what year your OMC is it's hard to say. I know that we had major problems with defective fuel pumps on 4.3 Mercruisers in the late 90s.

 

[billo001]

Re: Fuel Starvation

The boat is a 1995. When the engine quits the fuel filter is about half full of fuel. If I remove the relay and jumper the fuel pump it runs fine as long as the fuel filter is full. If the fuel filter is not full the pump will not pump even though it is running.

 

[SeaRay245]

Re: Fuel Starvation

im not really sure on this one but i wouldnt remove the relay sometimes there on there for safty reasons to shut off fuel in case of roll over

 

[billo001]

Re: Fuel Starvation

Could my problem be that the fuel pump is going bad?

 

[seahorse5]

Re: Fuel Starvation

The way the pump relay circuit works is by the starter solenoid yellow wire thru a diode when you crank the motor over. When the motor starts, the juice comes from a separate alternator circuit. The pump is not made to prime and can be damaged if run dry for even a minute. Check out your fuel system using a vacuum gauge, clear line, and a T fitting at the filter inlet fitting. If vacuum is above 4" Hg or there is air bubbles in the clear line, you have fuel system problems. Make sure to use a new OMC #502906 fuel filter, not an aftermarket one.