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Hello my name is***** read what you wrote but do not see any kind of model information. What are you working on?
Are you here?
Mercury engines are cataloged by serial number. Can I get the serial number on yours so I can run it and see exactly which version of the 40 you have.
Got it. Now are you loosing power to the pump or are you loosing ground to the pump?
Hello, my name is***** will assist you from here.
The ECU on this engine will allow the pump to run for only 5-10 seconds at key up. The pump then times out until a crank signal is recieved from the CPS to the ECU. So what you are seeing is normal.
Is there an issue with the engine other than this?
The ECU controls the ground signal to the pump telling it when to run or not.
When the engine stalls, is it actually losing fuel pressure, as checked on a gauge, or losing spark?
Ok, look at the left side of the valve cover, there are 3 relays there. One has a blue wire, one has a green wire, and the other should have a yellow wire to it. Take one of the other two and swap it with the one with the yellow wire to it. This is the main power relay. If the engine will not run, you will need to replace that relay.