Mercruiser 5.0 v8 efi fuel pump issue

[festamb1]

Hi could somebody explain to me how the fuel pump safety cut offs work please as i have a 1998 efi model which has a mefi 1 ecm fitted and i have power to the pump for 2 seconds when i put the ignition on and it will not start when turning over unless i put petrol down the throttle body then it starts up then soon dies, i think that i have an issue with either the fuel pump relay or oil pressure sender whats the best way of testing these as the Mercruiser manual states that there should be continuity between the screw thread that's goes in to the block and the screw terminal and i have none, other than linking this all out by wiring up the pump direct if there away of testing these 2 items
many thanks
mark

 

[Fun Times]

On EFI engine models the oil pressure sender/switch doesn't affect the fuel pump 12 power...That safety design is for carbureted engine.

Check every fuse you can locate on the engine and under the helm area...Also with the key switch on try tapping on the relays to see if you get the 2 second prime, along with wiggle the main wiring harness at the engine...Also swap the relays around with each other to see if things seem to change at key-up.

The ECM internally turns the relay on for 2 seconds at key-up if the ECM sees good 12 volt power and ground.

 

[festamb1]

Hi Fun Times this is the correct diagram for my engine is it still the case the oil pressure don't hold off the fuel pump and are both of the relays on my boat the same as there are 2 fitted.

Thanks
Mark

 

[Bt Doctur]

Locate the fuel pump and its wiring, verify that you have 12v at the relay. a ground supplied by the ECM closes the relay , that provides power to the pump

 

[Bt Doctur]

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