Yamaha F115 help please!!

[Superjetjim]

2003 Yamaha F115 outboard 347hrs

My outboard recently refused to start, I assumed VST filter or low pressure filters had blocked, I've stripped and cleaned them all, drained the tank and added fresh gas - still the same. Quick blaster of starter fluid and off she goes for a few seconds but then stops.

Identified down to fuel supply and the high pressure rail had no pressure. I then connected a 12v feed directly to the fuel pump in the VST (unplugged the lead and connected to the pins with crocodile clips and connected a small 12v battery I had) pump spun up and she started instantly. Looks like I've found my issue - question is how to I find out why I have no power to the fuel up pump? What do I need to swap out to fix this, a relay somewhere?

Thanks,

James

 

[99yam40]

You do not swap stuff, you test to see where the loss of voltage problem is

 

[Superjetjim]

Ok so should I be testing continuity between the pump (yellow/red and blue wires) and the corresponding wires at the relay at the front of the motor as a first step? I've downloaded the shop manual and it shows these wires entering the loom and being common in colour with the injector feeds all going back to the same relay. The engine runs (when power is applied to the fuel pump directly) so I guess the relay is working as the injectors have power. Would that therefore indicate a wiring fault to the pump and a good relay? Any other thoughts or things to check?
Thanks

 

[99yam40]

volt meter will show where there is 12 volt + and were it is not. work back to find were it stops.

Remember it also needs the negative to run the pump motor, If you find + to the motor then chase the neg

 

[Superjetjim]

volt meter will show where there is 12 volt + and were it is not. work back to find were it stops.

Remember it also needs the negative to run the pump motor, If you find + to the motor then chase the neg

Thanks, so the + is permanent and the '-' switched by the ECU, if the ECU is faulty could I just wire the negative to ground so the relay allows it to run whenever the motor is actually running? Seems to make sense to me but perhaps I'm wrong? In this scenario I would assume the pump would run when the ignition is 'on' and stop when the key is turned to 'off'?

 

[Superjetjim]

Just a quick update to say 'thanks' the issue was a break in the red / yellow wire from the high pressure fuel pump to the termination block under the flywheel - replaced that cable and she's back to normal! Woot woot, thanks guys
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