Help, Motor won't start. Merc 454 Mag EFI
 

So I have twins and this is what I've tried and narrowed down thus far.
Port Motor cranks, has spark, is pumping fuel to rail, no blown fuses found.

Turn the key on but do not get the warning sound, when I turn key it ticks like batt is dead but they're not. Changed safety switches from starboard side and same results. Port side sounds and fires right up. Both motors were running fine 3 weeks ago and have not used boat since.

I feel like some safety switch or something is keeping fuel from pulsing through injectors. Pulled one plug after cranking and was completely dry and no smell of fuel. Tried what seems like everything for 6 hrs on launch ramp and luck. Ruined a good day of boating. Need fixed if you have any advice, id appreciate it. Thanks guys

Did you check the starter fuse 100 amp??

i would say it,s the starter slave solonoid.pretty common problem.

No i did not, where is it? The motor turns over fine just won't start

Is this on the starter? As mentioned, motor cranks fine just no fire

No I didn't, where is that located and as mentioned the motor cranks fine, just no fire. Thanks

If it's the starter slave I believe you would get one single click. If the motor is turning over it's not the starter. When you turn the key to the ON position do you hear the fuel pump kick in?

The fuel pump is manual and the reservoir on top of motor is pressurizing. When I turn key I don't get the warning sound like I should. I turn the key to the run position and it makes a clicking sound at dash instead. The fuel rail has fuel, it's getting plenty of spark at plugs cause got shocked testing fire, but pulled a plug and was completely dry and no smell of fuel on it which lead me to believe no fuel is getting into cylinders. Not neutral safety cause motor cranks. Switched safety switches at dash and makes same noise. No warning beep.

I would check the grounds at the engine block from the negative battery, and the ground stud where engine harness grounds get grounded to. The alarm system gets grounded thru the engine. The alarm gets + power anytime the key is on. It goes off, when any of the circuit switches close, whether it be coolant temp, low oil pressure, fuel pressure, etc.

Chances are your alarm not working, has something to do with the engine not starting. The engine has a mechanical pump, but also has an electric pump. There is both a fuse and a relay for the electric pump. Again, this electric pump will not work if there is a bad ground. After winter time storage, is normally when these ground issues come up.

A test light, and wiring schematic will go a long way here. But I'd start with checking for clean ground connections. I believe the buzzer will have the purple wire going to one side, and tan/blue to the other. Tan/blue is the ground side. Before anything you can test for power with a test light at the purple wire on the buzzer with the key on. If you have power there, Leave the key "on", and play with those grounds back at the engine, listening for the buzzer to sound.

Thanks, I did switch out the safety kill with the one that's working for the Starboard but same results which let me to think it's not the safety switch. After putting it back on port the port fired up. The engine was just running 3 weeks ago for the first time after sitting all winter. I checked voltage on the starter slave solenoid and it's reading 12.5 so I know it has enough voltage. I opened the fuel reservoir nut (forgot what it's called) on top of motor and fuel was at top and a little air came out as well which tells me the pump is fine and pressurizing system. I still believe that fuel is not being dumped into cylinders because injectors are disabled at turn of key. Now what causes that is beyond my knowledge. Like you said it all starts at the key and warning horn