1998 5.0L Carb Mercruiser Alpha runs 30 seconds and dies

[Ken Dobkins]

I have a 1998 5.0L Mercruiser Alpha I/O with electronic ignition and 2 barrel carb.The boat has set-up several years, I have replaced most of the fuel system, fuel pump, filter, carb, fuel lines and fresh fuel, but the engine dies after 30-45 seconds, it does not appear to matter what rpm it is running, it dies as though it is losing ignition. Engine will retsart and continue dieing at approx 30-45 seconds each time. Any Ideas???

 

[Don S]

Re: 1998 5.0L Carb Mercruiser Alpha runs 30 seconds and dies

The oil pressure switch that controls the fuel pump is either defective, or the connections are corroded.

While cranking, the starter runs the pump and fills the carb, when you let off the key from the start position the electric fuel pump gets power from the oil pressure switch. The fuel in the carb will usually last 15 to 30 seconds.

 

[Ken Dobkins]

Re: 1998 5.0L Carb Mercruiser Alpha runs 30 seconds and dies

The oil pressure switch that controls the fuel pump is either defective, or the connections are corroded.

While cranking, the starter runs the pump and fills the carb, when you let off the key from the start position the electric fuel pump gets power from the oil pressure switch. The fuel in the carb will usually last 15 to 30 seconds.

View attachment 192134

would I see a drop in the voltage to the fuel pump if the oil pressure switch was failing ??

 

[Don S]

Re: 1998 5.0L Carb Mercruiser Alpha runs 30 seconds and dies

would I see a drop in the voltage to the fuel pump if the oil pressure switch was failing ??

I suppose you could, why do you ask?

 

[Ken Dobkins]

Re: 1998 5.0L Carb Mercruiser Alpha runs 30 seconds and dies

I suppose you could, why do you ask?

Thanks Don S, your advice was right, the Oil Pressure switch connections were the issue. I wish I would have tried this Forum a few weeks ago before spending all the time and money on the fuel system.