2012 Mercruiser 4.3 MPI fuel system problem/wiring diagram

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Opsguy

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My son's 2012 Hurricane boat outdrive was repaired by a shop in November 2016. The Mercruiser 4.3 MPI was running great when the outdrive broke. The boat was taken from the shop after being repaired and stored for the winter in another city. The boat was taken to his lakehouse on July 4 2017 and would not start. Also, he noticed the alarm "beep" did not occur upon switching the ignition on, as it always has, noting that diagnostics were OK on the engine. Now it will not start. We cannot hear the electric fuel pump come on to pressure the system. We can start the boat by spraying starting fluid into air intake, but only runs on the spray, dying immediately upon stopping the spray. The fuel line from the gas tank into the fuel/water separator filter is completely dry - tank is full of new gasoline. So we know the fuel pump(s) are not getting fuel into the fuel rails. We cannot find the fuel pump wires that must go to the pumps, nor do we have a wiring diagram to troubleshoot why the diagnostics are not running upon turning the switch on. Do you have suggestions on what are the likely suspects to look for that would prevent the fuel pump from getting power, or would cause the diagnostics to not run before startup? Which service manual do you recommend for us to get that will be the best, most detailed one for this Mercruiser system. Thanks for any help you may have to offer!
 

Fun Times

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This sort of sounds like either your fuel pump relay may not be working/stuck or the fuse to the fuel pump relay system is bad.

On top of the engine should be 2 (or 3) relays, try switching them around and see if the symptoms change any....Also try tapping on the relays in case they are slightly stuck internally form sitting.

Next to the relays and ECM area should be a little fuse box with a black cover over the top of the fuses. Remove the black cover and check your 3 fuses.
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Opsguy

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Thank you, Fun Times! Your input sure gives some things to check! And the wiring diagram is great, too. Thanks so much! It will likely be next weekend before I can get back up to the lakehouse to check those out - but I'll post back here with what we found out....
 

Gene W

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So having an issue with my 4.3 Mercruiser also. This sound just like what I have going on too. No power to the fuel pump. Switched relays no difference, checked fuses, all good. When I turn the key on the fuel relay clicks then 3 -4 seconds a second click. If I bypass the positive and negative wires, hook them directly to the battery it works. Any advice on what to check next ????
 
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