I have been experiencing occasional (twice in last year) situations where when its really hot (95 degrees) and I run the boat, moor it for an hour, and then run the boat again one engine dies of fuel starvation. Yamaha customer support clued me in to looking at the primer bulbs, and the continuous wave web site had an article that confirmed my suspicions that primer bulb orientation matters. I finally (hopefuly!) traced the problem to the primer bulbs having a horizontal orientation. In fact they were oriented with a slight downhill slope, when referenced to the fuel flow direction. The check valves need gravity to operate so if the bulbs are pointed downhill the valves will stay open and allow fuel to flow back into the tank and air to get into the fuel lines. The result is the engine dies of fuel starvation. So moral of the story - check the orientation of your fuel primer bulb and make sure the fuel flow arrow is pointing skyward.
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330 express fuel primer bulb orientation
- Thread starter choogenboom
- Start date
JUST-IN-TIME
Well-Known Member
I suspect horizontal is marginally OK whilst any orientation with a downhill inclination is not. Of my two engines, only one would fail in this manner and very infrequently at that. One of the bulbs was approximately horizontal and the other had a distinct downhill slope to it. Of the two engines, the one that failed was the one with the primer bulb that pointed downhill. I suspect that if the primer bulb is level that any fuel backflow will push the balls in the checkvalves enough to seal them. However if the bulb points downhill then gravity will pull the checkvalve balls open allowing gravity to slowly drain all the fuel back into the tank.
I also noticed that when priming/squeezing the primer bulb when horizontal that I was unable to get the bulb to harden up and I heard a distinct whooshing sound in the fuel filter which is upstream of the bulb. In theory, if the checkvalve is doing its job when squeezing the bulb there should be no backflow towards the fuel filter. The article on primer bulbs on teh continuous wave web site emphasized that the bulb works far more efficiently when used in a vertical position with the flow arrow pointed skyward.
I also noticed that when priming/squeezing the primer bulb when horizontal that I was unable to get the bulb to harden up and I heard a distinct whooshing sound in the fuel filter which is upstream of the bulb. In theory, if the checkvalve is doing its job when squeezing the bulb there should be no backflow towards the fuel filter. The article on primer bulbs on teh continuous wave web site emphasized that the bulb works far more efficiently when used in a vertical position with the flow arrow pointed skyward.
I don't buy that story one bit. The pump would pull fuel no mater what the orientation of the primer was. No air will get pulled unless there is a leak in the supply line or bulb.
The bulb could be bad and its check valve could be getting stuck but I don't see what running and then sitting has to do with it.
I suppose vapor lock could be an issue but not at the bulb.
I think it is something else. Does the motor smoke when it first starts (after failing)?
The bulb could be bad and its check valve could be getting stuck but I don't see what running and then sitting has to do with it.
I suppose vapor lock could be an issue but not at the bulb.
I think it is something else. Does the motor smoke when it first starts (after failing)?
BobP
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Makes no difference the bulb position except for when using it to pump fuel, it will not pump fuel the best or at all, unless it is properly positioned while you are squeezing it.
If a slug of air gets into the line, the fuel pump and systems in motor will evacuate the air automatically, not continuous air, but a slug.of air. Unless this is some new characteristics of the 4 strokes.
I find these statements entertaining at the least, and it's always the same, offered when the one responsible can't be bothered enough to figure out the real issue when he or she happens to be operating out of their capability and for whatever reason, won't ask for help from the more knowlegable.
Welcome to DIYer heaven -
Get a length of say 3 feet of clear 3/8 inch PVC hose from the depot, install it on the motor side of the squeeze bulb in series, get the splice hose fittings at the depot and clamps too, all together for a less than 10 bucks.
Now, run the motor and watch the clear hose, it will appear to be solid when viewing, only tiny bubbles you may see up close and they will be moving, if you see big bubbles (can see these from the bridge), you have an air leak in system on boat side of PVC hose. Report back here if you see bubbles and we will instruct you how to find the source.
If no bubbles, find another mechanic.
Don't leave the PVC hose in system permanently, only use for testing.
Good luck.
If a slug of air gets into the line, the fuel pump and systems in motor will evacuate the air automatically, not continuous air, but a slug.of air. Unless this is some new characteristics of the 4 strokes.
I find these statements entertaining at the least, and it's always the same, offered when the one responsible can't be bothered enough to figure out the real issue when he or she happens to be operating out of their capability and for whatever reason, won't ask for help from the more knowlegable.
Welcome to DIYer heaven -
Get a length of say 3 feet of clear 3/8 inch PVC hose from the depot, install it on the motor side of the squeeze bulb in series, get the splice hose fittings at the depot and clamps too, all together for a less than 10 bucks.
Now, run the motor and watch the clear hose, it will appear to be solid when viewing, only tiny bubbles you may see up close and they will be moving, if you see big bubbles (can see these from the bridge), you have an air leak in system on boat side of PVC hose. Report back here if you see bubbles and we will instruct you how to find the source.
If no bubbles, find another mechanic.
Don't leave the PVC hose in system permanently, only use for testing.
Good luck.
richie rich
Well-Known Member
WOW, is this Great Grady or THT! :lol: I thought I clicked the wrong shortcut.......
Bob, never knew it makes any difference in the position of the primer bulb, whether its for running or just priming, just make sure the arrow is going the right direction....the anti-siphon valve should take care of drain back.....what position for priming/running should it be in???
Bob, never knew it makes any difference in the position of the primer bulb, whether its for running or just priming, just make sure the arrow is going the right direction....the anti-siphon valve should take care of drain back.....what position for priming/running should it be in???
BobP
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I'm sick and tired of dealing with incompetant professionals, I would only know what incompetance is, because I'm informed.
Ignorance is bliss.
Unfortunately, I have been so cursed so it seems.
Have I told you the one about the pizza place owner: mechanic yesterday, pizza maker today ?
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Look at the squeeze bulb, there is an arrow on it, you point the arrow up.
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If you never had a problem using squeeze primer bulbs, forget this subject and thread ever existed.
Ignorance is bliss.
Unfortunately, I have been so cursed so it seems.
Have I told you the one about the pizza place owner: mechanic yesterday, pizza maker today ?
---------------------------------------------------------------------------
Look at the squeeze bulb, there is an arrow on it, you point the arrow up.
----------------------------------------------------------------------------
If you never had a problem using squeeze primer bulbs, forget this subject and thread ever existed.
richie rich
Well-Known Member
BobP
GreatGrady Captain
- Joined
- Apr 27, 2005
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- Reaction score
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- Model
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The ex-mechanic pizza maker, sold pizza business to retired cop, who lasted two months and went belly up.
I think the place is now a pet hotel.
Welcome to DIYer heaven !
I think the place is now a pet hotel.
Welcome to DIYer heaven !