Fuel pump problems. 305 merc

[esteym]

Hi, I have a electic fuel pump on my merc 305 carbed engine. Ive been having electrical problems, but have cleaned most of it up i think. The engine turns over, but when I stop, the fuel pump is usually on for a few seconds more. It never comes on and the engine does not start. I took a almost drained battery and hooked it up breifly. It ran and when I tried the engine again. It started for a couple of seconds. I took out my DMM and checked the connections. they seem good. I turned the engine over and checked to see if I have volts going to the fuel pump. Yes, it crested around 11volts. Should be 12. I checked the ground. I got a solid 12.2. <br /><br />Where should I look for further problems that would cause the fuel pump not to get enough power?<br /><br />Thanks <br />Mike

 

[Bondo]

Re: Fuel pump problems. 305 merc

The Fuel Pump is powered by 2 different circuits,.........<br /><br />When the Starter is Cranked,... It's fed from the starter,........<br /><br />After the motor Starts,.......... It's fed thru the Ignition Circuit,.. Thru an Oil Pressure cut-out Switch,.... It's located right down next to the Oil Pressure Sending Unit,.. Just forward of the block mounted Oil Filter Boss,..... Port-Rear Side of the engine.............<br /><br />If the engine(starter) is Cranking,..... 11V should be Plenty to get things Going,.......<br />I Doubt this is your Problem,....... but, You could try Jumpering it Directly to the Battery,... Atleast to get it Started.......<br />Or,... Just By-Pass the Oil Pressure Cut-Out Switch......

 

[Don S]

Re: Fuel pump problems. 305 merc

Look for the oil pressure switch that controls the fuel pump just above the blocks oil filter connection on the port side of the engine.<br />The pressure switch has 2 wires to it. Disconnect the wires from the switch and hook them together as a test. The pump should run with the ignition switch in the on position with the engine not running. If it does, start the engine for the final test to make sure it keeps running. If all seems ok, shut off the engine, disconnect the oil switch wires and get a new switch.<br /><br />