Fuel Primer Bulb Collapsing

[Finished Business]

Guys,

I've had a few problems with my boat regarding fuel this year. First it was the problem of water and debris. That's been solved. But moving on...

At full throttle for a couple of minutes, my primer bulb for the main engine compresses completely and starves the engine of fuel until it bogs down and dies. Until a recent conversation with a buddy, I assumed there was some other obstruction in the fuel line, or filters possibly. But talking with a buddy running a 225hp Yamaha (I run 250HO Etec) he was having the same problem, but at cruising speed. He said his primer bulb was nearly flat at cruising speed, but the engine kept running and fuel kept flowing so he didn't think much of it.

I believe my engine is moving a little more fuel than the 4 strokes, about 25-27 GPH, and after hearing his story, I am wondering if the fuel bulb is not capable of supporting the flow or PSI of the fuel passing through. The motor itself requires a certain PSI rated fuel line, which I have, but it did not mention the primer bulb. Doing some research online I've found that Tempo brand bulbs have a 60%+ failure rate out of the box. I'm not sure if what I have is a Tempo bulb, but I wanted to see if anyone else has monitored there fuel bulb when at cruising or WOT on new outboard engines and if the bulb stays firm or if it also collapses to some degree.

Before ripping apart my fuel system I'm thinking its wise to start with the easy to access and cheapest to replace and test...the bulb.

If anyone has an opinion as to where else the problem might be coming from, I am all ears.

My fuel system consists of two tanks. each tank has two lines running to a tank switch, so I can change tanks between both engines if I need to. After the switch both lines have a brass butt connector (as I had to lengthen the lines a little). From each set of lines runs into a fuel water filter. From the filter the lines run to the main and kicker engines, with a priming bulb in between.

I am going to point my bulb skyward, as also from reading it is important for optimum bulb performance to run it vertical so the line can be completely cleared of air. Horizontal or pointing down and there is a possibility of air staying in the bulb.

Can anyone offer an opinion or has monitored their fuel bulb and seem a similar issue of collapsing at high RPMS?

mucho gracias

-FB-

 

[Birdsnest]

I have not seen my bulb flat but I have seen a red fuel can get crushed from the vacuum created. Amazing. Those outboard motors will take their fuel no mater what.

 

[Fish Assassin]

Wrong diameter fuel line?
Obstruction at fuel pick up in tank or in line prior to ball?

 

[Aces]

Sounds like it may be sucking air. Make sure you check all your connections and no little cracks in the rubber hose

 

[RCA Dog]

Wrong diameter fuel line?QUOTE]

This.
There are a few ways around this problem, but this is most likely the root cause.

RCA

 

[Hookin'up]

I was thinking the exact opposite of Fishtofino,
if the tank is not vented properly (vented cap)
your creating a vaccum and something has to give, the weakest link being the ball?
just a thought, check the fill cap and make sure its vented properly and not plugged with crap, there should/will be a small vent hole in it somewhere possibly a rubber diaphragm style to keep water out at the same time
either that or the new motor is sucking fuel faster then the old vented cap was designed for and cant keep up?
the other possibility is too small fuel line as previously suggested, but I believe you say you are using what is recommended

 

[Rockfish]

Sounds like it may be sucking air. Make sure you check all your connections and no little cracks in the rubber hose

I was going to say the same thing. If motor has gas to start it and the pump is providing good suction, the bulb should get harder at higher rpm as the higher fuel pump suction increases pressure in the line, not flatter/softer. At least that is what the one for my main does. It pumps up somewhat but once the motor has been revved it goes hard and stays that way.

Have also seen a 5 gal plastic gas tank that someone did not open the vent on completely collapse from the created vacuum as the motor was ran over a considerable time period but obviously the bulb did not collapse first and cut off the fuel flow or the tank would not have collapsed.

 

[Finished Business]

more info....

the fuel lines are the correct diameter (3/8") recommended by Evinrude. I even went for the higher PSI line to be safe. They are all new lines with tight connections at every point. I did all the work myself so I can be sure of this.

The tank vent is below the filler necks, and vents both tanks. They connect to the vent at a Y connection 12" below the outlet. It is a 1/2" ID venting line.

FA mentioned an obstruction at the fuel pick-up, as did Trendsetter during our talks. I did have some debris come out of the tanks when first running the engines. Good thing for filters. The engine itself is very smart, according to the mechanic. And if anything but fuel entered the engine, it would give me a warning. The engine has water/fuel filter on it as well.

I did my best to clean the tanks of old fuel, and when emptying what I could (maybe 2L remained), the fuel came out clean with no debris...but it would be hard to remove the debris from the tanks, all I could think to do was turn them upside-down until the gas sloshed out the filler tube opening.

Is there a way to clear the fuel pick-up in the tank without removing the tanks? Possibly forcing gas through the line backwards to dislodge anything at the pick-up? I know this wouldn't remove the problem but its something for now...

It is a new engine so I assume the fuel pump is in full working order. But even new parts go bad but I think it is fine.

 

[Finished Business]

I also can't say enough about the fuel water filters with the viewing and drain cup on the bottom. Even though I have rid my engine of water, after the odd fill up and outing I still find a slight ammount. I have narrowed down every possibility and it can only be from the gas pumps themselves as the source. I would recommend one of these style filters to everyone.

PS Thanks for the quick replies fellas.

 

[Hookin'up]

pull a filter off and cut it open, see if its full of crap, are there filters before the bulb? check that one first, the problem should be between the bulb and tank, I believe the pump is creating a vacuum in the line due to obstruction or poor tank vent
as for clearing the pick up pull the fuel line off at the primer and blow compressed air through it at maybe 40psi max,

 

[Finished Business]

only filters before the bulbs. all new filters. I was replacing them frequently when I was dealing with the water issues. I would think a 1/2" breather would be suffient. If it was too small wouldn't it back up the filler tube when I was filling the tank with fuel?

 

[Hookin'up]

only filters before the bulbs. all new filters. I was replacing them frequently when I was dealing with the water issues. I would think a 1/2" breather would be suffient. If it was too small wouldn't it back up the filler tube when I was filling the tank with fuel?

just make sure the vent is clear, it may not back up in the filler if the tank can push air out the main filler around the nozzle
depends on the size of the filler neck and filler hose if its 1-1/2 or more it shouldnt spray back on you.
next dry day you get try and run it up to speed with the filler cap off and see if it still happens, at least it will eliminate a vent problem, then look farther downstream towards the tank for other issues, plugged lines or pickup from old crud,
could also be the check valve inside the bulb sticking too

 

[Rockfish]

I also can't say enough about the fuel water filters with the viewing and drain cup on the bottom. Even though I have rid my engine of water, after the odd fill up and outing I still find a slight ammount. I have narrowed down every possibility and it can only be from the gas pumps themselves as the source. I would recommend one of these style filters to everyone.

https://encrypted-tbn0.gstatic.com/images?

q=tbn:ANd9GcRUZ1KFfyW29_vDsnvCgIhXKK3OpOIc1s681jtmLOQkU3eihAyk

PS Thanks for the quick replies fellas.

Water can get into the tank from condensation forming on the inside of the tank. To minimize this keep you tanks full as much of the time as possible especially with large metal tanks. Don’t leave them three quarters empty over winter storage. Also check your filler cap as mine was letting in a little rain water past the messed up threads. The gas cap assembly has been replaced this year for several reasons. Also had to replace both Racors after 7 years down in the bilge with a salt water wash down system on the boat as the aluminum tops had serious corrosion problems (turned to white powder under the paint) to the point that the filter canister would no longer seal and leaked gas. Asked if I could purchase a more expensive Racor model with a stainless steel top end but they don’t make them. Planned lifespan I guess for more sales, like home hot water tanks.

 

[Hookin'up]

found a good read for you, touches on everything we discussed

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

 

[Sculpin]

Is the bulb new? Do you have a separate tank vent line going up to the gunnel etc.?

 

[Finished Business]

Bulb is new. Each tank has its own vent line.

Tim, I will try opening the cap when running to see what happens. Good idea. It is a 1.5" filler tube.

Regarding water in the tanks, I am running weekly, topping up each outing and still find the odd bit of water in the seperater. It is fuel from the gas dock so I am sure it is constantly replenished I'm guessing so its unlikely they have old fuel, but that's not to say it does not have water contamination for the same reasons small tanks would.

 

[Shermanater]

Looks like i'm having the exact same problem as you FB. I just finished podding my malibu and i put on a new 150 yamaha. The fuel line and primer ball is new from yamaha. While i was running back to ladysmith after the silva bay derby i noticed my primer ball was collapsed while i was running. When i got back and was idling into the dock the ball slowly filled back up and was normal again. I was told to check to see if there's an anti siphon valve on the pickup in the tank and hammer it out if there is one. Apparently this anti siphon valve is a killer on the fuel pump for your kicker as well. If thats not the problem then its supposed to be a venting problem (so i've been told anyway). I havent had time to look at mine yet but need to figure it out asap.

 

[Finished Business]

Great link. Nailed most points discussed.

I will be doing some work on the boat and taking a breather from fishing, and the fuel dock for a few weeks. There are about 10 things I've neglected since hitting the water and grinding out some fish, but with bigger trips in the future its time to address them before its too late.

 

[Finished Business]

Interesting sherman....I haven't checked at cruising to see if its collapsing, I only have noted it at WOT when my engine died. Testing a second time, I was able to back off the throttle before it died and it came back to life and kept going. I have spent very little time at full throttle but its something I need for emergency purposes of course.

 

[Shermanater]

I was only at wot for a short time to see what my rpm was and to see max speed. I think thats when it collapsed and it couldn't recover even at cruise. Once i was idling back to the dock it finally recovered and filled. That was saturday when i noticed it. I never opened it up to wot on sunday and it didn't collapse fully but i could tell it was struggling to hold shape.