Merc 115 4 strokes 2001 ECU/fuel pump problem

[Sylva-Ranger]

Merc 115 4 strokes 2001 S\N 0T340811 (Yamaha engine)

Hi everyone, hi have problem whit this engine
The hi pressure fuel pump run randomly, at the begining can run ok for hours and sometimes stop or don't start after shot off......and now run about 10% of the time .

The fuel pump is new (OEM ) about 2 year ago
when engine don't start, no voltage go to the ful pump
wire/connections beetwin fuel pump and ECU are ok
if i put the fuel pump on a battery, the fuel pump work and engine start.
Seem to be the ECU ...ECU is not available from Mercury, and from Yamaha is 2300,00 $ Can

My question : It is possible too feed the pump directly from the ignition swich whit some relays or other means ?

Thank you

 

[boscoe99]

Of course it is possible to power the fuel injectors (and other components) that normally get their power via the ECU. Using a simple relay as you suggest.

One word of caution is that you would want the relay control circuit to deactivate the relay power circuit at any time that the motor stops. This is to keep the fuel pump from running if the motor were to crap out or be stopped by the kill switch.

 

[alldodge]

The hi pressure fuel pump run randomly,

Have you tried replacing the relay, check clean and tighten contacts on relay?

Merc ECM's apply a ground to one side of the relay coil. When ground is applied the relay energizes and makes contact across 85 to 30 to power the FP

The pic below is not your motor but how the FP relay is powered most likely is. Most have 2 relays, main power and FP relays.

Main power is energized when key is turned to ON. This relay powers up the ECM and makes power available to FP relay and the ECM energizes FP by applying a ground for few seconds to prime. When key is turned to start the ECM looks for spark being activated and then it applies ground again

 

[boscoe99]

OP's motor is of Yamaha origin I believe. Power comes from the ECU for the injectors and a couple of other components. Or it is supposed to anyway.