Merc 5.7 260 question

[Godfirst]

Previous owner hooked up a electric fuel pump to this application to the stock carb the togo switch is in the dash I smell fuel starts right up but is this safe aftermarket setup?? Will check this out and the connections.

Thanks

 

[NHGuy]

Re: Merc 5.7 260 question

It must be a marine low pressure fuel pump, and the old pump needs to have been removed from the lower starboard side of the engine. The spot where the original pump was should now contain a block off plate.
You are correct to be concerned about fuel smell, should not be any.
So verify what type of pump it is and check for the fuel smell source.
If the pump isn't right it could be the problem, or if the needle in the carburetor bowl isn't sealing there could be too much fuel in there.
There should be a fuel pressure regulator in the system and the pump should only come on with the ignition.
You need hook up to the correct electric source instead of a switch. The right one will shut off the pump at the correct moment.

Folks who know more will come on, if no one does I can tell you more tomorrow, going to work now.

 

[akorcovelos]

Re: Merc 5.7 260 question

Check fuel pressure just before the carb, should be 6-7psi max. Carbs dont like high fuel pressure, so higher than 7psi will push fuel past the float needles and cause over fueling, which would cause the strong fuel smell. As already mentioned, none of that mstters if its not marine rated.

 

[Don S]

Re: Merc 5.7 260 question

the togo switch is in the dash

Togo switch ????? What is that? Did you mean toggle switch?

The electric fuel pump needs to be wired to an oil pressure switch and to the starter properly so it does not run unless the engine is running and their is oil pressure or the engine is cranking.

 

[Silvertip]

Re: Merc 5.7 260 question

You also need to know WHY the wiring needs to be through the oil pressure switch. Without that description you will very likely ignore the advice. If for any one of a number a reasons the engine dies the fuel pump will continue to run possibly pumping fuel into an engine or engine bay fire or just flooding the engine with fuel. In the latter case you attempt to start the engine and kaboom, an engine full of fuel erupts. Since the fuel pump, when properly wired, will not run until the engine builds oil pressure, there needs to be a start circuit around the oil pressure switch to allow the pump to run to initially pressurize the system. And just so you know, an oil pressure switch is not the same as an oil pressure sender. An oil pressure switch is similar to the one that turns on the idiot light in an older car.

 

[achris]

Re: Merc 5.7 260 question

.... An oil pressure switch is similar to the one that turns on the idiot light in an older car.

But works in the opposite direction. No current flow at low pressure.