Emergency Fuel Enhancement?

oneman546

Recruit
Joined
Jan 3, 2009
Messages
4
Would someone explain what the "Emergency Fuel Enhancement" on my '06 Yamaha TLR 90 does?

I was in a situation where the motor would start and rough idle for a few seconds then stop. I flipped the emergency fuel enhancement switch to "open" and the motor fired right up. Switch it back to the original position and the motor has fired right up every time since.

I'm very curious what it does.

Thanks,
Bryan
 

Dunaruna

Admiral
Joined
May 2, 2003
Messages
6,027
Re: Emergency Fuel Enhancement?

It is a bypass for the idle fuel circuit, usually means that the carbs are due for some TLC.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Emergency Fuel Enhancement?

its an enrichment circuit not an enhncement.
its purpose is to aide in cold start in the event of a themal valve failure.
what it does when placed in the open position is to manually fix fuel rich in addition to the idle circuits.
however if the idle circuits are plugged it will aide in running.
have the prime start system inspected and the carbs inspected and re read your operators manual.

your engine uses a system that automatically adjusts fuel for cold starts based on the temp of the wax pellet in the thermal valve unit, if a component of the automatic cold start circuit fails you can manually bypass the auto enrichment part of the fuel system and possibly start the engine.

using the warmup lever or if any carb linkage isnt correctly setup it will do funny things up to and including failure to start.
yamaha spent a lot of time and effort with the prime start system and on the 2 stroke 90 it works very well but most customers are not properly informed of how to start the engine or what the controls are for.
2 biggest failures of the prime start system are improper starting procedure and incorrect carb linkage synchronization.
 

Anthrsckmnd

Recruit
Joined
Jun 1, 2009
Messages
1
Re: Emergency Fuel Enhancement?

I just saw this topic and have read a lot of your previous responses to this topic, Rodbolt. I had two quick questions for you as you seem very knowledgeable on this. I recently bought a 90HP Yamaha 2-stroke in 2008. I have about 75 hours on the motor, but it has been getting really bad gas mileage and oil consumption. It's also fouled 2 sets of spark plugs within 70 or so hours. I took it in to our local dealer to diagnose this. They returned the boat to me and told me that the emergency fuel valve was in the "open" position. They turned it to "closed" and told me that this should fix our fouling and bad gas mileage issue. My 2 questions are, would running the motor with the emergency valve on "open" (and I am assuming a very rich fuel mixture) for 70 hours cause any engine damage? Also, should the switch be in the normal or closed position during usage? They set it in the "closed" position after I took it in. Thanks in advance for your help.
 

Fl_Richard

Lieutenant
Joined
Jan 21, 2005
Messages
1,428
Re: Emergency Fuel Enhancement?

I wouldnt think so... Just wont continue to foul the plugs.
 

Home Cookin'

Fleet Admiral
Joined
May 26, 2009
Messages
9,715
Re: Emergency Fuel Enhancement?

Rod and others, a related comment and then a question: I have a Yam 50, c. 2002, and its owners manual said not to lift the warm up lever when starting as it conflicted with internal engine set-up for starting; you can lift it after it starts. This is contrary to every other boat known to man, including my 2003 Yam 150. Being a multi-user boat (hunt club) I'm sure people do what's natural and lift it to start. This one sometimes won't start unless the tilt is all the way down. Ideas?
My 150 can be cranky to start and I suspect the electric choke (@ the key) isn't doing anything; the manual choke on the motor gets it going. It often has a hard time holding the start, so I do the warm up lever thing, try not to blast the motor but it does anyway, thus burning through the prime and I have to start all over. (My 1988 OMC 70 does the same but I expect it to be cranky.) Suggestions? Should I notice a difference when I push in the key and would there be a linkage that should move (like the old motors) that I can verify visually? (This motor is new to me).
 

Yarb

Cadet
Joined
Oct 5, 2009
Messages
12
Re: Emergency Fuel Enhancement?

its an enrichment circuit not an enhncement.
its purpose is to aide in cold start in the event of a themal valve failure.
what it does when placed in the open position is to manually fix fuel rich in addition to the idle circuits.
however if the idle circuits are plugged it will aide in running.
have the prime start system inspected and the carbs inspected and re read your operators manual.

your engine uses a system that automatically adjusts fuel for cold starts based on the temp of the wax pellet in the thermal valve unit, if a component of the automatic cold start circuit fails you can manually bypass the auto enrichment part of the fuel system and possibly start the engine.

using the warmup lever or if any carb linkage isnt correctly setup it will do funny things up to and including failure to start.
yamaha spent a lot of time and effort with the prime start system and on the 2 stroke 90 it works very well but most customers are not properly informed of how to start the engine or what the controls are for.
2 biggest failures of the prime start system are improper starting procedure and incorrect carb linkage synchronization.

Hello Rodbolt,
I am in the process of trying to get a pair of 1994 L250TXRS?s running. While doing some research on the fuel system I ran across your replies to several post. You seem to have extensive knowledge of the system and I have some questions.
These engines have been sitting for over four years. They are no starts now. They were running when it was parked so removing and cleaning all twelve carburetors is going to be my first step.
My questions are:

1. Does the electric fuel pump run continuously when the key is on?
2. Is the electric pump a diaphragm or centrifugal pump?
3. What pressure does the fuel pressure regulator maintain on the system?
4. What actuates the fuel solenoids and when are they activated?

Any other advice you might have to offer will be highly appreciated.

Thanks, Yarb
 

boscoe99

Lieutenant Commander
Joined
Aug 22, 2013
Messages
1,785
Re: Emergency Fuel Enhancement?

Rodbolt does not live here any more.

Take a look at the last time he posted.
 

Yarb

Cadet
Joined
Oct 5, 2009
Messages
12
Re: Emergency Fuel Enhancement?

Rodbolt does not live here any more.

Take a look at the last time he posted.

I noticed the date of his post, thought perhaps I would get a reply from someone who had the answers to my questions.
 

boscoe99

Lieutenant Commander
Joined
Aug 22, 2013
Messages
1,785
Re: Emergency Fuel Enhancement?

Yarb, your message was directed to rodbolt. If you are willing to take advice from anyone then it is recommended that you create a completely new post and throw it out there to everyone.

Even if I know the answer to a question, if it is directed to a specific person then I won't respond. That would be like me opening someone else's letter.

Good luck getting your motor fixed.
 

Yarb

Cadet
Joined
Oct 5, 2009
Messages
12
Re: Emergency Fuel Enhancement?

Yarb, your message was directed to rodbolt. If you are willing to take advice from anyone then it is recommended that you create a completely new post and throw it out there to everyone.

Even if I know the answer to a question, if it is directed to a specific person then I won't respond. That would be like me opening someone else's letter.

Good luck getting your motor fixed.
Thanks for the reply. I will enter it as a new post.
Yarb
 
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