Evinrude 9.9 Vacuum in Gas Line Issue?

[CSquid]

Hi. Newbie here. Glad I found such an informative place to discuss boating and related issues. I searched on this topic and din't see much there to help - so here goes:<br /><br />I have a mid 90's era Evinrude 9.9hp - 2 cycle. It runs for a few moments and then dies due to lack of gas. I just replaced the fuel line and the tank is also new. The tank doesn't seem to be the issue as I opened the cap to ensure there is no vacuum within the tank. The only way to keep it running is to disconnect the fuel line from the tank (you here a hiss as the vacuum is released) and then re-connect. What could cause the vacuum in the fuel line (which seems to be the issue) when its not being caused by the tank (again - happened when tank cap was open)? Is this classic fuel pump issue and, if so, is there any other way I can test to ensure that is the cause? I plan to take a friend and his son out after this is fixed and I hate to have another 1 hour+ trip back to shore as I had last Sat.<br /><br />TIA,<br /><br />CSquid (AndrewT)

 

[fireman57]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Are you sure that it is connected properly? Sometimes the fuel line seems to be attached but really isn't. Make sure that clip that snaps to the post is seated. You also might want to take your cover off and remove the fuel hookup and make sure that all passages are clear.<br />Does your primer bulb go flat from this vacuum?

 

[CSquid]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

I am certain that the fuel line is connecting solidly to the tank mount - the clip snaps in and is not loose. I will run tonight and check the primer bulb to see if it goes flat - I don't recall it did from last weekend.<br /><br />The tank mount has 2 small yellow prongs that get pushed in when the fuel line connects. I believe these are what allow air into the system. I guess I am not sure how they are supposed to work. Do they allow air into the fuel line to avoid a vacuum or do they allow air into the tank to avoid a vacuum or is there any difference? The reason I ask is that these two prongs are hard to push in and only partially depress when the fule line is attached and clicks in place.

 

[OBJ]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

CS....it would sound to me like the venting feature of the gas tank connection is not working. Can you aquire another gas tank to connect your fuel line to? If the problem goes away, the problem lies in your tank. The yellow prongs....one is for fuel flow and the other, as you surmised, is to vent the tank. It is possible that the fuel flow from the tank is being restricted, possibly through the connection on the tank.<br /><br />Did you replace the primer bulb along with the fuel line? There are two one way check valves in the primer bulbs that can fail.<br /><br />Keep us updated with anything else you may find...thanks.

 

[umblecumbuz]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Andrew,<br /><br />Adding my pennyworth - it might be a very stoopid question, but basic nevertheless - are you absolutely certain that the primer bulb is connected the right way round? I'm assuming you've done the fuel line job yourslf. There is usually a molded arrow on the bulb to indicate the direction of fuel flow - it only works one way.<br /><br />Apologies if that suggestion is too basic, but when all else fails, grasping at straws is what's left.

 

[BF]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Hi there & welcome!<br /><br />You wrote a pretty good description of the problem, but I just can't imagine how it's possible. If you connect the fuel line to the tank, and the line ends up having vacuum after running the motor, how can there not also be a vacuum in the tank?? When you opened the gas cap, did you actually remove it, or just loosen it? If it was sitting on top, it could be that a vacuum was still forming in the tank even if the cap was just sitting on the opening..<br /><br />As already said, it sounds like either a venting problem or a fuel bulb problem. If the fuel bulb was backwards (would happen if you just connect the fuel line the wrong way around), I doubt you'd be getting the engine going... Primer bulbs can fail, but you say it's a new line.<br /><br />So... I don't have much help I know, but I'd try running it again with the gas cap right off. If it can draw fuel through the fuel line, then the inside of the tank should have the same vacuum as the fuel line. Then I'd say the vent on the tank is not working. But... opening the gas cap should diagnose the problem (?).<br /><br />Good luck, & post when you find something else out.

 

[CSquid]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Good Questions and advice - Thx. I did replace the primer bulb with the fuel lines. I actually have bought two separate, new fuel lines and bulbs with the same problem on both so I can't imagine both bulbs are/were bad. And Yes - the bulb is installed with the arrow on it pointing to the engine as per instructions. Also, I did not completely remove the Cap when I checked the tank so maybe that is an issue. Will check again tonight.<br /><br />I kind of think its something with those yellow prongs. My friend used it the week before and said he had same problem and he just told me it worked when he manually held the fuel line into the tank mount. That leads me to believe that they are not venting properly when connected and snapped in place - but do vent when the connection is pushed in further and fully depress the vent prong. Could this make sense? And is there any way that the fuel connection to the tank can be modified to ensure the yellow prong is engaged?

 

[OBJ]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Yep....it makes sense. If this is a new tank, they are warranted.....if it's a Bomby tank. Take it back and explain the problem.

 

[Chinewalker]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Here's a relatively easy check for your fuel line and tank. Remove the motor end connector from the hose. Get yourself a clean coffee can. Place the fuel tank on a bench with the coffee can on the floor. Squeeze the primer bulb several times until you get a good flow of fuel from the end of the hose. Place the end of the hose in the can and allow it to siphon. If it siphons enough to fill the coffee can in a short amount of time, then you're good to go. If there's any sort of vacuum or restriction in the line, the fuel flow will slow to a dribble and stop within short order...<br /> To take the test a bit further, you can place the tank higher than the motor, hook up the fuel line to the motor, then remove the fuel filter cover from the side of the fuel pump. Place the filter in the coffee can and prime the bulb. You should get the same scenario as above.<br />- Scott

 

[OBJ]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

That's a neat idea Scott..... Dang I like it when I learned something.....

 

[umblecumbuz]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Another pennyworth Andrew, building on what's already been said:<br /><br />The fuel line from the tank to the motor is a single tube. The connector at the motor end is designed so that, when snapped into place, the valves both on the motor and the tube open, thus allowing free flow of fuel. These valves are just a convenience to stop fuel coming out or debris getting in when the line's disconnected. The only way for air to replace the depleted fuel in the tank is via the tank vent (sometimes a small tap in the centre of the filler cap, which should be opened whenever the engine is running).<br /><br />You can easily test that the line as far as the motor is operating correctly by unplugging the line from the motor, and depressing the stop-valve in the end of the line with a small screwdriver as you squeeze the bulb. <br /><br />If fuel exits cleanly, and continues to do so as you keep pumping, the problem lies either with the motor end of the valve or in the motor fuel lines, pump, or carburettor. If it doesn't, then you need to re-check the hose, bulb and tank lines. Presumably you've already unscrewed and checked the filter on the engine pump for crud?<br /><br />Incidentally, there ain't no such thing as 'vacuum' in the tank, otherwise it'd be as small as your fist - the correct term is 'depression'.

 

[fireman57]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

I think you have a bad tank. You said it was new. They have a rebuild kit for the connection portion of the tank but I would take it back and explain the problem and they should replace it or they will put a kit in it. I think you are correct that the one side is not pressing in sufficiently to allow fuel to the engine.

 

[CSquid]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

OK - Update: I borrowed another tank from the dealer and brought it home for comparison. It seems that the post on the tank mount that the fuel line clips (snaps) to is different between my tank and the borrowed one. The post on my tank mount sticks out much further than the one I borrowed. This means I think that the fuel line gets snapped and held in place in a position where the bottom post is not fully engaged in the fuel line (this causing fuel delivery issue). I think this is the problem. I plan to run some of the suggested tests given here just to make sure.<br /><br />I guess I am so used to looking for user error or some item that would wear and tear. In this case, this tank mount appears to be defective from the start in terms of design or assembly. Not what I expected to find.

 

[umblecumbuz]

Re: Evinrude 9.9 Vacuum in Gas Line Issue?

Hi again, Andrew.<br /><br />A simple tip to ease your life if you decide to check the tank-to-motor fuel line assembly, aka the suggestions above.<br /><br />Open out one end of a paper clip, and once you've unsnapped the fuel line from the motor, push it into the valve at the end of the line. It keeps the valve in the 'open' position, and saves the hassle of removing it. Instant tank, vent, bulb and fuel-line check.<br /><br />Moral: Always carry a paper clip in your get-you-home bag on the boat!