Vapor Lock?

[Duke]

Just had my first issue with a 96 G14. While driving it around a tractor show, it would all of a sudden just stop running after running just fine all day. After letting it sit awhile, it took off again. It did this 3 or 4 times. Each time I removed the gas cap and then kept running the starter for a bit. It seems as if the gas cap won't let air in the tank and when it gets enough of a vacuum built up, it won't pump gas. After priming the fuel line again, it takes off. Has anyone else had a similar problem?

[TheNewGuy]

On my G9 the gas cap is vented.

[Duke]

yea, mine is too. Do they go bad? I just can't imagine what else it could be.

[TheNewGuy]

If I remember right, there is a spring loaded ball in the gas cap. I had mine apart years ago and cleaned it out. See if you have any small screws on the underside of the cap.

[bordin34]

I think on my G16 if I take off the gas cap and shake it it will rattle.

[smallblock450sl]

Originally Posted by Duke

Just had my first issue with a 96 G14. While driving it around a tractor show, it would all of a sudden just stop running after running just fine all day. After letting it sit awhile, it took off again. It did this 3 or 4 times. Each time I removed the gas cap and then kept running the starter for a bit. It seems as if the gas cap won't let air in the tank and when it gets enough of a vacuum built up, it won't pump gas. After priming the fuel line again, it takes off. Has anyone else had a similar problem?

Your saying the starter and engine will "turn over all the time", but the engine won't "fire up" ? My 2 thoughts...First fuel...3 lines go to the fuel pump (from fuel tank/to carb and to the engine) the line that goes to the engine is called the "pullsar" line. the fuel pump runs off "crankcase pressure". I would take off that hose and "blow" back into the engine to see if there was any resticsion. Second spark...your cars ignition is "TCI/CDI" and runs "open and closed" ground for spark. I have "in my years" found several cars that "after getting warm" the circuit board soldering "flows away" from its contacts and you lose spark! Then when it cools down "the solder flows back and finishes the circuit" and you have spark again. Please, if try a spark test on a Yamaha from 1979 to 1995 (G1 thru G14) use a "dynamic spark tester" it will show if spark is good and constant and will protect the "TCI" from beaing damaged. I hope this helped in some way. Good luck and keep us posted. Dave

[Duke]

Thanks for the advice SmallBlock. I did the fuel line test and we are getting gas just fine. It hasn't acted up since Saturday, but then we have'nt driven it for as long a period yet. If it persists, I will try the spark test. Thanks again.

[smallblock450sl]

Originally Posted by Duke

Thanks for the advice SmallBlock. I did the fuel line test and we are getting gas just fine. It hasn't acted up since Saturday, but then we have'nt driven it for as long a period yet. If it persists, I will try the spark test. Thanks again.

Your welcome. One more "fix" on the fuel system though....Your fuel pump should be "round", correct? Try taking the "cover" off the fuel pump. the cover is the inlet for the pulsar line/hose. I have seem many covers (on the inside) with a white chaulky looking substance and it can restrick the pulsating need to drive the fuel pump. You see as you drive, it losens the the stuff and stops the fuel system, sit for a while and it works again. If this is the case, you can buy the new cover that has been coated (green). Make shure to "mark" the outside edges of the fuel pump so you can get it alighned and the screws back in. I know it's a long post, but I wanted to let you know why I suggested it and the easiest way to do it. Good luck and keep us posted. Later Dave

[Duke]

smallblock,

It acted up again this weekend, wouldn't start at all. I started at the gas tank and work my way all the way to the carb by literally blowing through all of the fuel lines, including blowing through the fuel pump. After that, started right up. I was wondering where to get that fuel pump cover you mentioned, I'm thinking that might be the problem. Also, thanks for the advice.

[spriddle]

Have you checked the line coming off the back area of the engine (I believe) that actually blows a little air into the fuel pump to keep it pumping. If I remember correctly, it controls the fuel flow. I think it is a 5/16 hose.