bulb flat - but seems not to be a venting problem

[TigerMo]

I've got a fuel flow problem that has me stumped. Yamaha 100hp, 4 stroke on a Whaler Outrage 17' with internal fuel tank.<br /><br />It happened the first time after a few hours on the water, running and stopping to fish. On the way back in at full throttle, the engine died, and the bulb was flat and no amount of playing with it would bring it back full. Opening the fuel fill cap didn't help. Thinking the gauge was bad and we were out of gas, we got the towboat to bring out some fuel. We added about 15 gal and took off for about 3 minutes - same thing happened - flat bulb, and opening the fill cap did no good (got towed on in).<br /><br />I replaced the in-line fuel filter cartridge and the water-sep spin on filter (both on the internal tank side of the bulb). Things seemed ok, the bulb would pump and inflate back up and the engine ran. To be on the safe side, I got a 6 gal portable tank with its own fuel line. <br /><br />Out again - happened again, this time while idling at the ramp waiting to pull out at the end of the day, after running at full speed on a short trip of about 15 minutes. We switched to the portable tank - bulb went flat on it. Different fuel line, different bulb, and not running through any of the filters. Just in case the little vent valve on the cap wasn't working we unscrewed the whole cap on the portable tank - still a flat bulb.<br /><br />Any thoughts? Thanks for your input.

 

[ob]

Re: bulb flat - but seems not to be a venting problem

Hey Tigermo,Sounds like a case of murphy's law.Only things I can figure would cause your problem are <br />1-restricted pickup tube in tank<br />2-defective anti-syphon valve on tank fitting<br />3-defective primer bulb<br />4-too small i.d fuel hose<br />5-improper venting<br />I realize that you have checked and attempted to rule out most of what I listed.However there has to be some sort of restriction upstream of the primer bulb for it to colapse.I'm out of ideas.

 

[clanton]

Re: bulb flat - but seems not to be a venting problem

I almost never work on a Yamaha. Check the fuel lines between the engine cowling and fuel pump. If a quick connect, check the connection. All portable tanks do not have a 1/2 inch pickup tube, check pickup tube and fitting of portable tank. If you got the second primer bulb from the same place as the first one, you may have 2 bad primer bulbs. You said filter and water seperater ahead of bulb, the engine should have a small filter on the side of block somewhere, which makes 3 filters for the pump to pull fuel thru, too many. You have to check every fuel line and fitting from fuel pump to tank. you can use a fuel pressure/vacumn gauge from sears, with a T fitting from discount auto, splice the T in fuel line run engine anything over 4/5 inches vacumn is too much. Start at fuel pump intake side, move to connector at engine cowling, move to output side of primer bulb, intake side of primer bulb, to filters and tank fittings.

 

[steelespike]

Re: bulb flat - but seems not to be a venting problem

It should be a pretty simple problem.If the vent is working there must be a restriction between the tank and bulb.Anything from a plugged <br />strainer in the tank to a bad valve on the tank end of the bulb.<br /> Something plugging the line<br /> something kinking the line<br /> If you are trying to lift the fuel too far.<br /> any thing causing the fuel not to flow.

 

[Yepblaze]

Re: bulb flat - but seems not to be a venting problem

It's not impossable to have a bulb that's just too smooshy.<br /><br /> You might try a firmer on. Heck it could only cost a couple a dollars to try.

 

[Bear]

Re: bulb flat - but seems not to be a venting problem

Topic: Johnson 70 fuel problem <br /><br />From what you said I think the fuel lines are the problem. Try a different brand. Or a firmer bulb as Yepblaze said. <br /><br />The two different tanks, fuel lines, bulbs etc and no filters the second time tells us something. If you tried a portable tank (and fuel lines and bulb) from another Yamaha 100, and still got the same flat bulb, third time... Can you borrow from someone?<br />You are saying that no part were the same on the second try? Is it a Yamaha 100 fuel tank or another brand? <br /><br /> Marine hoses

 

[Bear]

Re: bulb flat - but seems not to be a venting problem

...or something kinking the line as Steelspike said. Near the engine but before the bulb I'm thinking. Do you have enough space there. Did you reroute the fuel line on the second try?

 

[TigerMo]

Re: bulb flat - but seems not to be a venting problem

Thanks for all the comments.<br /><br />The second tank is a small 6gal portable tank with its own fuel line and bulb, not running through any of the filters. That's what makes the problem so difficult - independent system from the engine connector to the second fuel tank, but same problem. <br /><br />Since that could mean I'm doing something wrong in each setup, I'm getting someone else to look things over to see if I'm missing something. If they don't see anything obvious I'll start replacing parts and checking the vacuum on the lines.<br /><br />Also, both bulbs were purchased at the same time so I guess its possible they both could be defective. So I'll try a whole new line/bulb (pre-made by the manufacture rather than one I put together) on the portable tank and also try the portable tank on someone else's outboard to see what happens.<br /><br />Thanks again for all the tips and input.

 

[alcan]

Re: bulb flat - but seems not to be a venting problem

Hi Tiger<br /> I've never done this, But is it possible that the bulbs are hooked up backwards?

 

[clanton]

Re: bulb flat - but seems not to be a venting problem

You could start and warm engine, remove primer bulb, and insert a connector in place of the primer bulb, then run engine with a primer bulb. if it runs ok, bulb is bad. Connector must be proper size.

 

[jim dozier]

Re: bulb flat - but seems not to be a venting problem

I don't have the answer here but something is wrong with the picture. From the original description as posted the problem whatever it is is between the bulb (but including the bulb) and the fuel in the tank. The anomaly here is the problem reoccurs with a new tank and line. The problem as described is still between the bulb and the fuel in the 2nd tank although I don't know what it is we know where it is. You got a low pressure on the engine side of the bulb induced by the fuel pump collapsing the bulb because something is restricting flow into the bulb. What the something is is complicated by the fact that a 2nd tank and line with bulb caused the same problem. Something is missing in the decripiton here. It sounds like the solution is going to require dismantling the fuel system from the bulb to the fuel(tank) to find out where the problem is. Are the fuel lines (both) detachable and have you installed (both) backwards? The bulbs are one way flow. If both lines were installed backwards so the bulbs were backwards the fuel pump would close the bulbs against the one way valve wouldn't it? Just a thought.

 

[TigerMo]

Re: bulb flat - but seems not to be a venting problem

Backwards bulbs or some toher install mistake seems logical, except that the engine runs for a while (in the last case, about 20 minutes at full throttle) before pulling the bulb down on the internal tank. Just looking at the internal tank, it seems like a classic case of the tank not venting right or a strainer on the tank pick-up getting clogged up.<br /><br />But the problem with the second tank really threw me for a loop. I think I've got to see if I can duplicate the problem with another portable tank and fuel line that is known to work on another engine and then go from there. <br /><br />It could be a strange case of bad bulb (or bad install) on the portable tank, and a bulb problem, venting issue, or clogged pick-up on the internal tank.<br /><br />Thanks again for the comments and suggestions.

 

[Backlash]

Re: bulb flat - but seems not to be a venting problem

Hey TigerMo,<br />I can't add to what's already been said, but I sure hope you'll let us know what the problem was when you finally find it. Like the others, I'm puzzled by the fact that the problem also manifests with the independant tank. <br />Backlash

 

[DJ]

Re: bulb flat - but seems not to be a venting problem

TigerMo,<br /><br />You did not say if the portable tank was vented. <br /><br />If it's a plastic one, they ususally have screw vents on the filler cap.

 

[TigerMo]

Re: bulb flat - but seems not to be a venting problem

Portable tank was vented - we even unscrewed the whole cap in case the little vent screw wasn't working - still same result.

 

[Bear]

Re: bulb flat - but seems not to be a venting problem

Edit.

 

[45_red]

Re: bulb flat - but seems not to be a venting problem

Saw a similar problem on a yamaha 115; fuel pump diaphram had a hole in it. Don't know how that could cause a flat bulb but fixing the pump seemed to cure it.Good luck

 

[bent rod]

Re: bulb flat - but seems not to be a venting problem

I had a similar problem with one of my 200 yamahas. What i found was the connection at the cowling was the problem.I took it out and installed a hose connecter and that took care of my problem. worth a try.

 

[TigerMo]

Re: bulb flat - but seems not to be a venting problem

update - water seperator filter and filter on the engine were dirty. <br /><br />I can understand the filter on the tank side of the bulb causing the bulb to go flat. But the second tank, not going through the water sep. filter, with it own fuel line bulb going flat is still a mystery unless the engine filter was part of the problem, even though that filter is on the "wrong" side of the bulb to cause the problem.<br /><br />Thanks again for all the input.

 

[jim dozier]

Re: bulb flat - but seems not to be a venting problem

You live in the Twilight Zone, this sounds like a case for an X-file to me. Glad you got it fixed.