9.9 4 stroke hard cold start

[big ken]

hi i just purchased a 91 yamaha 4 stroke model t9.9exhp , the only way i can start it is to spray fuel into carb, must do this a few times. once it is running it is ok all day, motor has been sitting for a while in basement but was suposed to have been fogged etc. there is no choke that i can see of and it is electric start only. what do you think could be wrong? thanks ken

 

[big ken]

Re: 9.9 4 stroke hard cold start

allright ive narrowed it down to a choke issue. this motor has no pull choke so it is either a electic or maybe some sort of vacume, when i hold a piece of paper over carb it will start right up then slowly slide paper off. is anyone familiar with this motor? what makes this choke work? until get a mannual thanks ken

 

[big ken]

Re: 9.9 4 stroke hard cold start

man i guess i should have bought a johnson or evinrude lol thanks anyway

 

[big ken]

Re: 9.9 4 stroke hard cold start

ok did find out my motor has a fuel inrichment on side of carb. if i take off plastic cap on it and press plunger down it will start. what is causing this not to work while cranking over engine? anyone??? thanks ken

 

[big ken]

Re: 9.9 4 stroke hard cold start

man eighty something views and no advice? WOW!!!

 

[Daviet]

Re: 9.9 4 stroke hard cold start

I don't work on yamahas, but by looking at the parts breakdown for your engine I don't any external operation of what I would call a cold start valve.
Maybe it is something you have to manually activate for cold starting.
I am surprised that no one has joined in as of yet. Maybe you could contact a dealer and ask some questions about the cold start procedures for your engine.

 

[big ken]

Re: 9.9 4 stroke hard cold start

I don't work on yamahas, but by looking at the parts breakdown for your engine I don't any external operation of what I would call a cold start valve.
Maybe it is something you have to manually activate for cold starting.
I am surprised that no one has joined in as of yet. Maybe you could contact a dealer and ask some questions about the cold start procedures for your engine.

thanks for the reply, i did find out that it is called a fuel inrichment and the air valve has 3 bimetal somethings in it and it senses block temp and ambient air temp, also was told that this carb was just a bad system and always had problems cold starting and was told they have a updated carb assembly for this problem, afraid to see how much that is, already paid 900 for motor, but once started is a very sweet motor, again thanks

 

[sdsaw]

Re: 9.9 4 stroke hard cold start

big ken,
Found you a few posts explaining how the automatic choke works on this motor.
Depending on it's age, there are a vacuum operated enrichment system and an electro-thermal valve system. I'm not sure what year they switched to the electro-thermal system.

http://forums.iboats.com/showthread.php?t=293037&highlight=carb+enrichment+valve

http://forums.iboats.com/showthread.php?t=140418&highlight=carb+enrichment+valve

If you have the vacuum enrichment system, I might be able to help you by making sure that you have the hoses routed correctly and how to test the components.
I have a shop manual and a 1988 electric start model that I've worked on over the years.
If you have the electro-thermal system, sorry, I don't know jack about those!

Scott

 

[big ken]

Re: 9.9 4 stroke hard cold start

big ken,
Found you a few posts explaining how the automatic choke works on this motor.
Depending on it's age, there are a vacuum operated enrichment system and an electro-thermal valve system. I'm not sure what year they switched to the electro-thermal system.

http://forums.iboats.com/showthread.php?t=293037&highlight=carb+enrichment+valve

http://forums.iboats.com/showthread.php?t=140418&highlight=carb+enrichment+valve

If you have the vacuum enrichment system, I might be able to help you by making sure that you have the hoses routed correctly and how to test the components.
I have a shop manual and a 1988 electric start model that I've worked on over the years.
If you have the electro-thermal system, sorry, I don't know jack about those!

Scott

thanks scott. i have the vacume system, i will check out your posts, i seemed to have temporarily fixed it . when motor is running the plunger stays in the down position, when not running it goes up. when i pop off the cap and manuslly press plunger down and slide the lock on it it starts and runs fine. just need to figure out while plunger doesnt pull down when cranking it. thanks ken

 

[sdsaw]

Re: 9.9 4 stroke hard cold start

Ken,
When the plunger is in the up position, the enrichment circuit is activated. It will be in the up position while cranking.
As the motor warms up, the plunger will pull down and the fuel mixture will lean out. There is a B.V.S. valve that is monitoring the head temperature that will open and close, allowing vacuum to control the plunger.
My manual has six pages explaining how this carb works.
It does mention that if you have removed the thermostat or it is stuck open, the enrichment circuit will always be on (plunger up)
There are 2 diaphragms that pushes or pulls the plunger up or down (could possibly be torn) providing the other components are functioning correctly.
When everything is working correctly, it works very well in my experience.
I wouldn't be buying a new carb just yet.
A factory manual is a must for this motor.
Scott

 

[big ken]

Re: 9.9 4 stroke hard cold start

Ken,
When the plunger is in the up position, the enrichment circuit is activated. It will be in the up position while cranking.
As the motor warms up, the plunger will pull down and the fuel mixture will lean out. There is a B.V.S. valve that is monitoring the head temperature that will open and close, allowing vacuum to control the plunger.
My manual has six pages explaining how this carb works.
It does mention that if you have removed the thermostat or it is stuck open, the enrichment circuit will always be on (plunger up)
There are 2 diaphragms that pushes or pulls the plunger up or down (could possibly be torn) providing the other components are functioning correctly.
When everything is working correctly, it works very well in my experience.
I wouldn't be buying a new carb just yet.
A factory manual is a must for this motor.
Scott

thanks scott. your first post you sent me was very helpful in explaining the function of this enrichment system, i just cant figure out why it wont start when plunger is up if that riches the fuel but will start when i manually push down on plunger if that leans it out, it will stay down when running and goes up when shutting motor off. if i push down plunger and lock it with the little slide it has on it it will start every time, just dont know if it will run rich in this position when warm? what will be the best mannual i can i can buy and where can i get one?. thank you very much for your help ken

 

[sdsaw]

Re: 9.9 4 stroke hard cold start

thanks scott. your first post you sent me was very helpful in explaining the function of this enrichment system, i just cant figure out why it wont start when plunger is up if that riches the fuel but will start when i manually push down on plunger if that leans it out, it will stay down when running and goes up when shutting motor off. if i push down plunger and lock it with the little slide it has on it it will start every time, just dont know if it will run rich in this position when warm? what will be the best mannual i can i can buy and where can i get one?. thank you very much for your help ken

" if i push down plunger and lock it with the little slide it has on it it will start every time, just dont know if it will run rich in this position when warm?"
Can you start it with the plunger locked in the down position when it is cold? You are running the lean mixture that a warm motor requires.
If you can start it cold without the rich mixture, I would think that you can run it this way.
Did you check for a properly working thermostat?
Try adjusting the idle mixture screw?

"what will be the best mannual i can i can buy and where can i get one?"
The best manual to get would be the factory workshop manual.
I remember seeing some posts on where to order them from. Do a search on this forum and it should show up or contact a Yamaha dealer to see if they can order you one.
Good luck, Scott

 

[sdsaw]

Re: 9.9 4 stroke hard cold start

Found these:

For $10, this may be worth a try and no waiting
http://imracingmanuals.com/yamahaoutboardmanuals.htm

Some discussion on manuals
http://forums.iboats.com/showthread.php?t=226518&highlight=factory+manual

 

[big ken]

Re: 9.9 4 stroke hard cold start

Found these:

For $10, this may be worth a try and no waiting
http://imracingmanuals.com/yamahaoutboardmanuals.htm

Some discussion on manuals
http://forums.iboats.com/showthread.php?t=226518&highlight=factory+manual

thanks scott! i will check into those manuals. the only way it will start cold is with the plunger down. its like you said when motor is not running plunger is up the second it does start the plunger goes down, i will check into thermostat thanks ken