Fuel Primer Bulb–Reverse Flow, Losing Prime

[boatnamesue]

Brief backstory: I recently installed a new fuel tank and fuel lines. Prior to this installation, when I go to prime the engine for the first ignition of the day the bulb is always empty. I've heard from others that their bulb remains full, or at least not completely empty. Since installing the new tank it's taken a lot more squeezing of the bulb to prime, maybe a dozen or so squeezes before bulb begins to fill.

Today was different. I would squeeze the bulb until my forearms were on fire, still no fuel. Eventually for some reason it began to fill, but moments later the fuel would reverse and the bulb emptied. Bad primer bulb?...sure, probably. I bought a new primer bulb, installed. I experienced the same issue. Kept squeezing till it eventually filled. This took about 2-3 minutes of squeezing to fully prime.

Dropped the boat in the water, started, all good. Ran the boat around for an hour or so. Stopping every so often, shutting down, and checking the bulb. During this time the bulb would remain partially full, which is normal.

No fuel leaks anywhere, plenty of fuel in tank, fuel pump functioning properly. Few questions:

* Primer bulbs have check valves, right? They prevent fuel from reversing flow. If this is correct, and the primer bulb is new....what's happening here?

* Fuel pump....are there also check valves in the fuel pump that prevent reversed flow from carb bowls?

* Even though the fuel lines are new, IF there was a puncture in the fuel line between bulb and tank, thereby pulling air instead of fuel, I would notice this fuel leak as it flowed into my bilge. So i'm really at a loss for what's happening, why it takes so many squeezes of the bulb. I had to look at the fuel gauge a few times because it seemed as if the tank was empty. Your thoughts on possible causes and what to look for?

* There seems to be debate on whether the fuel/water separator should be located between the tank and bulb or between the bulb and engine. If someone knows the definitive answer to appropriate location, please reply and detail its reasoning for location.

[Capt. Bob]

Light reading.

http://continuouswave.com/whaler/reference/primer.html

For the record, my bulb is located downstream of my fuel filter/water separator and mounted vertically (arrow up). It takes ten 'squeezes" to prime my 91 carbed Yamaha. Since I rarely operate the boat on consecutive days, I have to squeeze each time I go out.

[GoneFission]

It sounds like one of your hose connections is loose and you are sucking air into the line somewhere.  Sometimes new hose will seem tight, and then the clamps or hose will relax a bit and let some air in.  Some folks double clamp fuel connections to prevent this.  The fuel pump and also the bulb will pull air before it pulls fuel.  Check your connections and clamps - make sure they are all well-seated and tight...

[MarshMarlowe196]

I also have my fuel bulb routed like Capt Bob described, with the primer bulb vertical, flow direction pointed "up".  This works fine most of the time, but it can be a real PITA to fill an empty fuel/water filter canister with the bulb after the filter. I'll probably redo it eventually so the bulb is ahead of the canister, so filling a new empty canister will be easier

[Capt. Bob]

Just a thought Jessie,
I've been filling my new filter with fuel before screwing it on. Seems to help.

[boatnamesue]

It sounds like one of your hose connections is loose and you are sucking air into the line somewhere.  Sometimes new hose will seem tight, and then the clamps or hose will relax a bit and let some air in.  Some folks double clamp fuel connections to prevent this.  The fuel pump and also the bulb will pull air before it pulls fuel.  Check your connections and clamps - make sure they are all well-seated and tight...

I've got metal hose clamps on all connections.  But you make a valid point...perhaps a connection has loosened since first installation.  I'll check these connections.  Obviously I cannot visualize the pickup line connection to fuel tanks fitting, this being under the hatch.  This particular connection I used 2 hose clamps, as well as sealing the threads around the 90º brass elbow.  I find it unlikely air could be pulled in there.  However, with that said, the air leak could only be coming from one other connection....fuel pickup line–bulb.  This line is brand new and doesn't come in contact with anything that could puncture line.

[wingtime]

Tip #1 hold the arrow pointing skyward so gravity helps pull the check valves closed until fuel reach the bulb.

#2 Primer bulb after fuel filter. Just prime the bulb before changing the filter AND prefilled the new filter with fuel. I've never had a problem priming after changing filter (see tip #1)

#3 ALWAYS buy name brand OEM primer bulbs (Mercury or Johnson Evinrude) After market ones just don't last work work very good compared to factory bulbs.

The needle and seat in your carbs should help back flow (when the floats are full) as should the check valves in your fuel pump. It should not take that many pumps to prime your motor, you must have an air leak. If you can get rid of the hose clamps and replace them with Oetiker style  crimp clamps. You can get a setting tool set from Amazon. They seal MUCH better than worm gear clamps. Since they cannot be reused be sure to carry a handful of hose clamps in your onboard tool kit incase you have to replace one while at sea...

OH tip #4 carry a small tool kit onboard for emergency repairs.

[boatnamesue]

Tip #1 hold the arrow pointing skyward so gravity helps pull the check valves closed until fuel reach the bulb.

#2 Primer bulb after fuel filter. Just prime the bulb before changing the filter AND prefilled the new filter with fuel. I've never had a problem priming after changing filter (see tip #1)

#3 ALWAYS buy name brand OEM primer bulbs (Mercury or Johnson Evinrude) After market ones just don't last work work very good compared to factory bulbs.

The needle and seat in your carbs should help back flow (when the floats are full) as should the check valves in your fuel pump. It should not take that many pumps to prime your motor, you must have an air leak. If you can get rid of the hose clamps and replace them with Oetiker style  crimp clamps. You can get a setting tool set from Amazon. They seal MUCH better than worm gear clamps. Since they cannot be reused be sure to carry a handful of hose clamps in your onboard tool kit incase you have to replace one while at sea...

OH tip #4 carry a small tool kit onboard for emergency repairs.

My primer bulb is oriented in such a way that it is always vertical, with arrow pointing up.  My fuel/water filter is located post-bulb.  There seems to be a lot of debate as to where this filter should be located, and I've yet to come across scientific data that proves where it should be located.  When I bought the boat/motor this filters position was located post-bulb, so that's where I've kept it. 

When i next get to the boat, what I'll do is prime bulb till firm and place a handled tubing clamp on the fuel pickup line just under the tank side bulb. If I lose prime, the leak is coming from above clamp. If prime holds, its coming from below clamp. And I'm hoping its not from below clamp cause that means removing console and unsealing fuel hatch. Ugh.

I'll check into those clamps you mentioned, thanks.

[wingtime]

BTW Racor suggests the primer or any "transfer" pump should be located after the filter. The reson is the pumping action can emulsify the water in fuel and/or force it thru the filter.

[Blue Agave]

BTW Racor suggests the primer or any "transfer" pump should be located after the filter. The reson is the pumping action can emulsify the water in fuel and/or force it thru the filter.

^This

[Levi]

There's a restriction somewhere between the fuel tank and filter or motor. My poly tanks have a small valve on the outlet/ feed side of the tank. I've seen aluminum tanks with the same small valve. I'd check this before I went any further.
Remember lefty loosy righty tighty applys to valves also.
I have also had bees / wasps lay eggs inside the vent port.Check there too.

[boatnamesue]

Wish I could report back with what the problem was.  The past two times using the boat the primer bulb would become firm after only squeezing 5-6x.  So I don't know what was going on, perhaps it was the primer bulb I replaced.

[mshugg]

. . . .perhaps it was the primer bulb I replaced.

It's happened before.

[minionsram]

Wish I could report back with what the problem was.  The past two times using the boat the primer bulb would become firm after only squeezing 5-6x.  So I don't know what was going on, perhaps it was the primer bulb I replaced.

Trust me, you are not the only one who has pulled hair out and trouble shot fuel issues for it to be just the primer bulb. That is why I only use the factory made ones right now. I have had an Atwood one go bad in two months. I now have the omc/ johnson evinrude one on my motor and keep a spare in the tool bag.