Power to my fuel pump???

[Camaro4life18]

I have a 4.3L Carb Alpha that is stalling and starving for fuel. I think it might be a bad fuel/water separator, but I'm dumbfounded with the electrical to the fuel pump. With the ignition OFF, I have 8v of Power going to the pump. Traced back to a diode that must be bad because it has 13v before the diode. I traced all the way back to a 20amp fuse and gave up before the sun went down. Why is there power when the ignition is off?

 

[Bt Doctur]

There should not be a diode on a mercruiser. The fuel pump get no power unless there is oil pressure or from the outboard lug on the starters solenoid

 

[Fun Times]

What year is the boat/engine?

Try unplugging the oil pressure switch down by where the oil filter ought to be and see if the power stops at the fuel pump...A stuck on oil pressure switch under pressure could continue power.

 

[Camaro4life18]

The boat is a 2005, but I'm guessing an early model because it is not an MPI.

There is a diode, because it is in the factory harness.

Traced out the power and it goes back to the slave cylinoide. I think the bad diode wore out my fuel pump.

 

[Bt Doctur]

The boat is a 2005, but I'm guessing an early model because it is not an MPI. Then carbd, or TBI, no power feed should come from the slave wiring.

 

[Bt Doctur]

what manual number are you seeing this in

 

[Camaro4life18]

I'm learning more about what I got, it is the 4.3L TKS. The best looking wiring diagram I have found so far is this one someone made up...
https://forums.iboats.com/forum/eng...r-i-o-and-inboards/10460074-tks-module-wiring

None of the diagrams I have seen from Mercruiser show the diode in the wiring diagrams, but I see the diode in the parts catalog for the 4.3L Carb Alpha model.

However I'm not so sure it still looks like what mine does...which may mean someone wired mine wrong.