Check Valve???

[Kmort]

I recently bought my first boat with an I/O and it has a Mercrusier 4.3L V6 Thunderbolt engine and is a 1995. There is a primer bulb in the fuel line which needs to be used to start when cold. I've been told by several that it is not suppose to be there so I took it out and ran a straight line. I couldn't get gas to the carb so I put the bulb back in. I've been told that there is a check valve to keep the fuel from draining back into the tank and is probably not working and it is why someone put the bulb in. Anyhow, I've been told that this check valve is in the carb and I've been told it's at the outlet from the fuel tank. Which is it? And any other ideas????

 

[Howard Sterndrive]

Re: Check Valve???

outlet from the fuel tank.

that.

it is part of the barbed fitting the fuel line connects to at the tank

 

[JustJason]

Re: Check Valve???

There may or may not be an antisiphon valve. Which is a check ball designed to keep fuel from siphoning out of the tank should a hole in the fuel line happen. It is not designed to keep fuel from flowing back into the tank.

You do not used primer bulbs on IO's

If you feel you need one because fuel is draining out of the line when the boat sits then you have either an air leak in the boat side fuel system or a fuel pump that's on it's way out.

 

[Bondo]

Re: Check Valve???

If you feel you need one because fuel is draining out of the line when the boat sits then you have either an air leak in the boat side fuel system or a fuel pump that's on it's way out.

Ayuh,... Or the Weber 4bbl. that bleeds off when sittin'...

 

[rodbolt]

Re: Check Valve???

or a quadra jet that the mainwell plugs are leaking.

 

[jerryjerry05]

Re: Check Valve???

The tank on I/Os should have a anti siphon valve.Outboards NO.
Take the one out and inspect it.Try sucking through it.If it offers no resistance,then it's bad replace it.
The fuel pump might be weak and not have enough suck to bring fuel up on start up.Once you squeezie it to the carb it will work because the motor is turning a lot faster than at start up.Ethanol can ruin your pump and hoses.Making them soft and mushy not allowing fuel through.J

 

[Don S]

Re: Check Valve???

You have an electric fuel pump. Does it run when you crank the engine? It should, but some automotive starters didn't have the terminal for that wire on them, therefore the pump may not run when you crank the engine.
You also shouldn't have the primer bulb in the fuel system on an IO.
That check valve is an antisiphon valve to prevent fuel from siphoning out of the tank if a hose breaks. It has nothing to do with keeping fuel in the fuel pump or hoses. YOu have a water seperating fuel filter on your engine, it alone will prevent fuel from siphoning back to the tank, but that back saiphon is NOT your problem.
A fuel pump pressure gauge will tell you if the pump is working, and how well, when cranking.

 

[Kmort]

Re: Check Valve???

You have an electric fuel pump. Does it run when you crank the engine? It should, but some automotive starters didn't have the terminal for that wire on them, therefore the pump may not run when you crank the engine.
You also shouldn't have the primer bulb in the fuel system on an IO.
That check valve is an antisiphon valve to prevent fuel from siphoning out of the tank if a hose breaks. It has nothing to do with keeping fuel in the fuel pump or hoses. YOu have a water seperating fuel filter on your engine, it alone will prevent fuel from siphoning back to the tank, but that back saiphon is NOT your problem.
A fuel pump pressure gauge will tell you if the pump is working, and how well, when cranking.

How can I tell if the pump is running at crank?

 

[Kmort]

Re: Check Valve???

If you feel you need one because fuel is draining out of the line when the boat sits then you have either an air leak in the boat side fuel system or a fuel pump that's on it's way out.[/QUOTE]


Air leak in the boat side fuel system? Can you explain the in more detail. I'm not sure what exactly that means. Thnaks

 

[Don S]

Re: Check Valve???

Air leak in the boat side fuel system? Can you explain the in more detail. I'm not sure what exactly that means. Thnaks

Read this thread, I think it will help you understand what you are looking for, and how to find it.

http://forums.iboats.com/showthread.php?t=283269

 

[Kmort]

Re: Check Valve???

WOW!!!!

Thanks Don!!!!!

 

[rodbolt]

Re: Check Valve???

jerryjerry05
please go read some USCG regulations BEFORE one of us flames you in public.
otherwise very shortly I am going to call you something on a public forum and then the moderators will bite me, again.
please help me from being bitten.