Fuel pump power problem

[bitofhog@netzero.net]

I have a 2004 Mercruiser 5.0, carbureted engine that wont start. It kicks over on starting fluid but that is all. I assume a fuel problem. I can't hear the fuel pump run when the key is turned on. I found a burnt 25 amp fuse under the dash and replaced it but the fuse box doesn't say anything about what the fuse is actually for so I am not sure if that went to the fuel pump or not.
So my first question is: Is there a fuel relay on the carb version of this engine? If so, I can't find it. The reason I ask is that I took the electric clip off the fuel pump and turned the key on and I don't see any power going to the pump. I don't want to replace the fuel pump if it is a power issue.
Q2: Since there isn't a computer on this boat to run the engine. How does the fuel pump know when to turn off. It can't just run all the time right?
Q3: Is it safe to run 12 volts the the pump directly just to see if the pump runs?

Any help would be greatly appreciated. I don't know how to run down this problem.

Serial OM673298


tom

 

[Bt Doctur]

Have the engine serial number makes it easier to answer

So my first question is: Is there a fuel relay on the carb version of this engine? If so, I can't find it. The reason I ask is that I took the electric clip off the fuel pump and turned the key on and I don't see any power going to the pump. I don't want to replace the fuel pump if it is a power issue.

The fuel pump power is controlled by a oil pressure switch ,just turning the key on does not power the pump

Q2: Since there isn't a computer on this boat to run the engine. How does the fuel pump know when to turn off. It can't just run all the time right?

It stops when you turn the key off or you have no oil pressure



Q3: Is it safe to run 12 volts the the pump directly just to see if the pump runs?

Yes

 

[bitofhog@netzero.net]

Thanks for the quick response. If I crank the engine enough would the oil pressure come up enough that I could see power going to the pump? I am just trying to make sure this isn't the problem before I move on to pump replacement.

 

[Bondo]

If I crank the engine enough would the oil pressure come up enough that I could see power going to the pump? I am just trying to make sure this isn't the problem before I move on to pump replacement.

Ayuh,.... Welcome Aboard,..... The fuel pump is powered from 2 directions,.....

As BD says, the ignition circuit power runs through the O/P switch, probably located down Low, mid-block, port-side, to the fuel pump,....

Also, the start circuit powers the fuel pump, When the starter is engaged, from the tiny terminal, outboard side, on the starter's solenoid, to the fuel pump,....

 

[Scott Danforth]

I would simply apply 12 volts to the pump and do some trouble shooting