1970 oddest carb problem ever...

[smevil]

Ok here it goes, 1970 Evinrude carb fresh rebuild, new float, needle seat all new gaskets, etc. this problem has been on going for months, after you put the carb back together and prime the fuel bowl you hear the fuel fill the bowl, then primer bulb gets tight, as normal. Then turn key engine runs perfect. Second and third day go to prime the bulb you get 1/4 sqeeze on gets tight engine still runs perfect. Here is the problem day three maybe four you go out prime the fuel bulb and it will take 5-7 squeezes after that the fuel will start flowing out the top atmosheric hole on top fwd of the carb.
This has done this time and time again same senario, been in this thing 20 plus times, the one thing that is curious to me is after the 3 day window you go to prime the bulb you have to fill the carb bowl of fuel (you can hear it going in) again the first couple days all is fine, then its like the fuel disapperes out of the bowl you fill it back with the bulb then out the top it comes. I already know it coming out the top when it takes several squeezes of the bulb. Have bench tested the carb every way imaginable the needle and seat shuts air off when blowing perfect. One other thing I can't get my head around is where does the fuel go first couple days the bowl remains full but after that it disappears, should it not stay in the for days if not weeks? SME

 

[fireman57]

Re: 1970 oddest carb problem ever...

I have found that if the engine is running well there is no reason to anger the outboard gods by questioning something. Seems every engine has it's quirks.

 

[smevil]

Re: 1970 oddest carb problem ever...

Well it runs fine, hot laps around lake are good but as soon as it has its issue, thats all it does it pumps right out the top by the fuel pump. Then I take the carb back off and starts the cycle over, I know this seems crazy but me and brother are stumped and we have been aircraft mech for 20+ years, not saying we know it all cause we dont, but were pretty crafty guys. Plus its the most simple carb I have ever meet.

 

[Daviet]

Re: 1970 oddest carb problem ever...

Do you tilt the engine, could the fuel be running out.
The only thing that controls fuel flow into the carb is the needle/seat, when you rebuilt the carb did you replace the needle/seat, did the needle have the rubber tip opn it?

 

[fireman57]

Re: 1970 oddest carb problem ever...

also when you replaced them did you make sure that the float was level when turned upside down?

 

[smevil]

Re: 1970 oddest carb problem ever...

Yes sir it is level set up to run in a large trash can, and yes to new rubber tip needle and seat plus new float, and tested with air flow and the needle shut it off 100 percent every time. even tried to overpower the needle valve with high press. but it helds good. thought the fuel pump was to strong but not the case. basically i know its going to fail if the primer bulb gets a full squeeze. told you it was crazy.

 

[Daviet]

Re: 1970 oddest carb problem ever...

Try putting a white paper towel under the carb and see if you can find the leak, a carb will not run out of fuel through evaporaton in a couple of days, it has to be leaking out somewhere. If you get fuel out of the bowel vent, the needle/seat has to let excess fuel into the carb, you did install the nozzel gasket in the center of the carb didn't you?

 

[smevil]

Re: 1970 oddest carb problem ever...

Nozzle gasket actually a homemade one, I hate to admit but it seemed to work better than the one that came in the rebuild kit. But correct me if im wrong but would that not let un-metered fuel into the stand pipe and in turn engine would run rich? Please enlighten me.

 

[Daviet]

Re: 1970 oddest carb problem ever...

Correct, just trying to eliminate any leakage points.

 

[lexer440]

Re: 1970 oddest carb problem ever...

Is it possible that a rough spot or maybe a gasket edge is interfering with the smooth operation of the float?

 

[halfmoa]

Re: 1970 oddest carb problem ever...

I have found that if the engine is running well there is no reason to anger the outboard gods by questioning something.

This is my new favorite quote. Thanks fireman57!