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Yamaha 99hp 4stroke startingrunning problem

S

silverwolf

New member
I have cleaned carb. and repla

I have cleaned carb. and replaced fuel pump. Engine will start and run for a couple minutes then die. If i squirt fuel in intake will keep running. Any ideas what could be wrong?
 
checked carb float needle valv

checked carb float needle valve? will motor keep running if you pump the bulb? checked fuel tank vent?
 
"The carb is full of fuel and

"The carb is full of fuel and motor will not keep running pumping the valve. The fuel tank vent is open. If I hold a couple fingers over the air intake it will keep running. I just finished takeing the carb apart and rechecking all passages and they all seem to be ok but, stil acts the same way. It has me baffeled.
Thanks for the input, need all the help I can get."
 
"the fingers over the intake s

"the fingers over the intake says that it is a lean mixture problem, so when you choke the intake with your fingers it makes the mixture richer and it keeps running. sure acts like a dirty carb/plugged jets. Hopefully one of experts on this forum,like Just-In-Time,will have some ideas for you. I'll be very interested to hear what this problem is. Good luck!"
 
"Thanks much, I think it is a

"Thanks much, I think it is a lean mixture also but, can't find anything plugged. Will keep trying. Thanks for the info."
 
"Your carby has three circuits

"Your carby has three circuits to it an idle, intermidiate, and a high speed, you have a blockage or a bad air leak, you could spray some starter fluid around the carby\manifold area and see if the motor picks up"
 
Thanks for the info. I don&#39

Thanks for the info. I don't find an air leak and thought I had cleaned the carb real good. I have now filled the float boal with sea foam to see if that helps.
By the way the electric thing on top of the carb. Is that just an electric choke or does it have any other function? I am not sure it is working.
 
Hope the Seafoam treatment hel

Hope the Seafoam treatment helps but I'll be very interested to know what is causing the problem. Is your gasoline fresh and clean? maybe start with some fresh fuel with Seafoam in it? No air leaks anywhere in the fuel lines? This will probably turn out to be something obvious like a plugged carb jet. Good luck!
 
"I have done the fresh gas thi

"I have done the fresh gas thing and with sea foam in it, even put premium gas in it. It is an interesting problem but starting to get on my nerves a little. I have pushed fine wire through every orfice in can find with no avail. Thanks for responding."
 
Well thanks to all for your in

Well thanks to all for your input. I replaced the fuel pump to no avail. The secondary idle jet was slightly plugged which caused it to die as soon as the electric enrichment selonid started warming up and closed off the starting circuit. Man oh man I learned quite a little on this operation. Got the thing adjusted and is working like new.
Thanks for all the input.
 
"I think I might have a simila

"I think I might have a similar or opposite problem. My 9.9 will start beautifully and run well at any RPM for 4 to 7 minutes. Then it starts to miss fire badly at anything above idle and stinks like gas. It it will keep this up for maybe 10 minutes, then eventually clear itself and run beautifully again at any RPM for hours and hours. When it is miss-firing, it seems like it is not getting enough air. Been through all he carb cleaning steps. Gas is not the issue since I have been dealing with this for two years and many tanks of gas. Both plugs have good spark consistently and both cylinders have reasonable compression. Seems like something electronic to me. I do not really understand how the three stage carb and enrichment solenoid all work together. The mixture problem only seems to kick in when in the intermediate and high speed ranges since it will idle pretty smoothly at all times. Anyone have any ideas."
 
Yamaha 9.9 starting and runnin

Yamaha 9.9 starting and running issues. I have had nothing but problems with my motor and frankly am convinced that no one has a clue as to why these problems occur. Yamaha shops are less informed than the owner that attempts his repair through trial and error as well a pile of cash in parts will be blown with every visit to a marine repair facility. Anyone looking for a perfect condition carb for a T9.9.$600.oo bucks worth. Open to offers. You do not need to know the name of the Yamaha dealer that screwed me with this one.Has anyone got the real actual Yamaha specs for testing coil values^ Please do not reply with I think or maybe answers please. Simple...The actual meter read values and the procedure only.
 
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