Vanguard 303777-1111 : Runs great then sputters and dies

[derost]

The engine has all of a sudden developed a problem of running fine and strong, then crapping out. I have replaced the head gaskets as they were leaking, done standard tune up, replaced fuel filter, and have thoroughly cleaned the carb 3 times. In fact I just cleaned it again yesterday, getting every hole and crevice cleaned out with fine wire and brake cleaner. Turn the key and it runs strong, absolutely purring. Run it around the property for 5 minutes and all is good. Five minutes later it is coughing, coughing.... dead.

Thoughts?

 

[ILENGINE]

I would either suspect the fuel pump is not working properly, which is a rare issue so don't look there first. Or there is a fuel flow restriction in the tank or fuel hose causing it to not flow enough fuel to supply demand.

 

[derost]

I think that is a good suggestion. I'll drain the tank and replace the line to see what I see. Thanks

 

[shurguywutt]

Check the fuel cap make sure it isn't building a negative vacuum inside of the tank. Vent may be clogged. You can check by loosening/taking off the fuel tank cap while it is running and see if it doesn't die.

Also something that has happened to me before when I took apart a carb I messed up the orientation of one of the gaskets. It was 90% correct when it was flipped but one of the breather openings was missing since it was flipped. This caused the engine to die once it got warmed up. Once it cooled it would work fine again. That was annoying and hard to figure out.

 

[slomo]

Trash in the fuel tank. Flush, shake and blow the tank out. If yours has a 90 degree hose barb on it, make sure that is clear.