C40TLRX Yamaha Prime Start System question

[99yam40]

Can anyone else tell me if there is suppose to be liquid fuel pumped out of the line to the intake from the prime start system when the switch is in the normal position and the motor is being turned over cold. Mine does not in the normal position, but it does in the open position.

And if it is not suppose to be pumped out, is it suppose to suck liquid fuel through or just vapors? Mine seems to be just tied into the top of the center carb, because when I blow air into the line it comes out of the vent at the top of the carb without bubbling through any liquid that I can tell.

[boats.net]

Some fuel will come out hose going to manifold but don't think it should come out hose going to carb, thats the air vent.

[99yam40]

The line I am taking about is the one to the manifold from the prime start assembly.
When motor is cold and after I pump the primer bulb and fill the bowls. I can pull a vacuum on the line I take off the manifld and get no liquid fuel out of it just fumes/air when the switch is in normal. After the prime start assembly if warmed up this line plugs off as it should. even turning over cold will not pump liquid out of this line.
When I switch to open there is liquid fuel pumped out when motor is turned over cold which is the emergency part of it to be able to run when the idle jets plug up , at least that is what I think it is for.

[boats.net]

I would check the diaphram and primer assy to make sure is clean and is working.

[99yam40]

The diaphragm and the heater unit work.
I have taken apart and cleaned as I have cleaned the carbs several times.

The diaphragm pumps fuel out. but only in the open position not in the normal.

The heater unit heats up and closes the passage to the line to the manifold after running for a while and I even tested it off of the unit and measured the movement as the manual states.

I have had someone tell me that it will not pump fuel out when in normal but will suck fuel into the manifold while running.

This is why I am asking if it is designed to suck liquid fuel or just fumes to enrich the motor while warming up?

[99yam40]

The diaphragm and the heater unit work.

The diaphragm pumps fuel out. but only in the open position not in the normal.

The heater unit heats up and closes the passage to the line to the manifold after running for a while and I even tested it off of the unit and measured the movement as the manual states.

I have had someone tell me that it will not pump fuel out when in normal but will suck fuel into the manifold while running.

This is why I am asking if it is designed to suck liquid fuel or just fumes to enrich the motor while warming up?

[boats.net]

It's not a pump and does rely on manifold vacuum to enrich fuel.

[99yam40]

Thanks for the reply boats.net,

I have been told both ways,
1. that it will pump out and
2. it has to be sucked out by motor vacuum.
I know it will pump liquid fuel out in the open position and am now fairly confident it has to be sucked out in the normal position, but I am still wondering if its designed to suck liquid fuel up through the line or just fumes

[99yam40]

I thought I would post a few sketches I made of the Prime Start System to help others see how it works and find out if others think these are correct or not.
This is the way I believe the system works judging from what passages are open and which are closed during the different switch positions while the system is cold.
My findings are that in the normal position the motor sucks a fuel and air mixture into the manifold through the line (I installed a clear vinyl line in place of the factory one for testing, but did not see any liquid flow.)
I did see a solid stream of liquid fuel pumped into the manifold when switched into the open position.
when in the closed position both the vent line and the line to the manifold are plugged off and have no flow.http://www.yamahaoutboardparts.com/a...15373-off1.jpg
When warmed up the needle will plug the orifice to stop the fuel flow in the normal position and also restricts the air flow through the vent to the carb..
The layout may not be exact, but the flow concept should be correct.

any comments on corrections are welcomed