idles and dies

[buddyo61]

2005 9.9 4 stroke. starts up fine and idles smoothly for about 20 secs. and dies. Have to wait for 10 minutes for it to start again and the same thing. Can anyone help with this please.

 

[Jake_MN]

Re: idles and dies

Start with the easy stuff...

Obstruction in the fuel line that prevents the carb from refilling quickly enough? Blocked vent in gas cap that causes partial vacuum to form?

Disconnect the fuel line to the carb and see if gas flows freely. If not, loosen the gas cap and see if that starts the flow.

 

[buddyo61]

Re: idles and dies

o.k. Jake I'll try that. Thanks

 

[Jake_MN]

Re: idles and dies

Sounds good. One other thing, does your fuel line hold pressure? When you pressurize the bulb does it stay firm? A small leak would not kill a running motor, but if there is a larger leak that could be a problem. It would be obvious when you try to pump up the bulb. If none of the above apply, post back and we'll go from there.

 

[buddyo61]

Re: idles and dies

Jake, when i disconnected the fuel line from the fuel pump to the carb. the motor run idled great. I mean it ran for at least a minute before i shut it off.make any sense to you?

 

[Jake_MN]

Re: idles and dies

I'd strongly suspect an obstruction in the fuel line or gas cap. With the fuel line off (or gas cap off) your engine is able to pull fuel freely from the carburetor bowl. With it on, a partial obstruction causes a vacuum to form in the carb bowl as the fuel is drawn up into the venturi. It doesn't take much of a pressure drop inside the carb to offset the pressure generated inside the venturi. Take the gas cap off and see if it will still idle for a couple of minutes. If it will idle with the gas cap off, but not with the cap on, then the cap is your issue. If it won't idle with the gas cap off, but will with the fuel line disconnected I'd look to the fuel line next.

 

[buddyo61]

Re: idles and dies

Jake, I'm sorry, I should have told you I had the gas cap off with no resultant change in performance. As far as the fuel lines go when watching fuel being pumped from the fuel pump I wasn't impressed. Do they go bad often?

 

[Jake_MN]

Re: idles and dies

No worries. So the gas cap makes no difference, but removing the fuel line allows it to idle for longer than normal?

If this is correct, then you're likely looking at your fuel pickup and fuel line. They can and do get fouled. Sometimes via internal breakdown, sometimes through garbage they pick up. If you'd like, you can always try removing the primer bulb, flushing both sections of line, the bulb, the fittings and the pickup.

 

[buddyo61]

Re: idles and dies

Are you talking about the fuel line and pick up from the tank to where it connects to the motor. Sorry to be so dumb.

 

[Jake_MN]

Re: idles and dies

Not dumb, this can be a bit confusing. Basically what's happening is that when your fuel line is disconnected from the engine (at the fitting where it mates to the engine) it appears that the fuel is able to flow freely from the carb bowl up into the carb throat and then into the engine. So we know the carb itself does not appear to be restricting fuel flow.

Given that disconnecting the fuel line allows fuel to flow freely from carb bowl to engine, we likely have a restriction somewhere between the hose fitting that attaches to the motor and the fuel pickup that is actually in the tank. This restriction is causing a partial vacuum that stops flow from the carb to the engine. By removing the gas cap to see if that helped we eliminated a clogged cap as a potential vacuum source.

So, working backwards from the fuel line fitting that attaches the fuel line to the motor we have

1. that fuel-line-to-motor fitting
2. the section of hose between fitting #1 and the primer bulb
3. the primer bulb
4. the section of hose between the primer bulb and the gas tank
5. the fitting that connects the fuel line to the gas tank's fuel pickup
6. the gas tank fuel pickup

Easiest thing to do would be to replace the gas line. They're cheap and in doing so you're addressing items 1-5. If this solves the issue you're done. If not, you should suspect the fuel pickup.

However, if you'd like to do some tinkering, you can disassemble the clamps that hold the fittings, bulb and line together and give them a good flushing to see if that helps out. Also look inside the gas tank to see if the fuel pickup looks to be covered in crud or otherwise obstructed.

 

[buddyo61]

Re: idles and dies

Going to give a rest today. I forgot to tell you the gas tank, fuel line & bulb assembly is new. Bought a new line/bulb assy anyway to eliminate that . No change but I did notice it is hard to connect the fuel line from the tank to the cowling connection. It's like there is a lot of back pressure keeping it from connecting.

 

[Jake_MN]

Re: idles and dies

Strange. Do you still have the old fuel line? I wonder if taking the engine connector off the old line and swapping it onto the new line will help.