2014 F90 hard to start when engine is hot

[rodbolt17]

and never forget to simply check the basics.

I got involved in an F115 recently.
they had gone through the fuel system and even swapped the ECU.

symptom was lack of power but would eventually reach 5700 RPM.

took me less than 15 min to diagnose the issue.
and this was after I had been up over 28 hours then got about 2 hours of shuteye before trouble shooting it.

but the computer said all was well.

[pstephens46]

Would there be any long term consequences to simply opening the throttle 25% when starting under the "rich" condition?

I have been doing this for 5 years.....

[pstephens46]

and never forget to simply check the basics.

I got involved in an F115 recently.
they had gone through the fuel system and even swapped the ECU.

symptom was lack of power but would eventually reach 5700 RPM.

took me less than 15 min to diagnose the issue.
and this was after I had been up over 28 hours then got about 2 hours of shuteye before trouble shooting it.

but the computer said all was well.

So what was the issue?

[boscoe99]

Would there be any long term consequences to simply opening the throttle 25% when starting under the "rich" condition?

I have been doing this for 5 years.....

No adverse issues at all. Those that are getting long in the tooth remember the good old days of carburetors. Where it was common for the motor to get flooded with too much gasoline. The cure was to press the pedal to the floor and crank away. As soon as the incoming air cleared out the excess gasoline the motor would start up. Same thing with an outboard motor. Just be prepared to come back on the throttle quickly so as to not over speed the motor.

It is my understanding that EFI automobiles are designed so that if the pedal is to the floor when the motor is being cranked that the ECU will shorten the pulse width of the injectors. It has been trained to know that this is the sign that the engine might be flooded, so the ECU does what it knows to do to help cure the flooded situation.

Maybe someone with a Yamaha EFI wants to do a test for us. That is, intentionally flood the motor by adding enough gasoline that it won't start. Then fully open the throttle. Then crank the motor. Maybe YDIS will indicate that the injector pulse width is less while the motor is being cranked.

[pstephens46]

I'm about 400 miles away from my boat. Can't help this week.

Thinking about also removing the damper seal in the lower unit and running it a bit. Curious if there are any noticeable effects.

[sthomasIV]

and never forget to simply check the basics.

I got involved in an F115 recently.
they had gone through the fuel system and even swapped the ECU.

symptom was lack of power but would eventually reach 5700 RPM.

took me less than 15 min to diagnose the issue.
and this was after I had been up over 28 hours then got about 2 hours of shuteye before trouble shooting it.

but the computer said all was well.

removed the vst vapor shutoff valve and cleaned it with carb cleaner.

texted last tech who worked on it and his response was this............"new fuel cooler was added with vst, vapor shut off valve was not replaced but I checked it with the engine cold and after running in test tank, iac was also checked while at the shop, I had hooked up to the computer while running so I could monitor what was goin on the whole time"

i took it to lake and like clockwork it still does it. tried unplugging the vst vapor shutoff valve. only thing that did was let it idle at about 1100/1200 rpm's but still would not start on first attempt when motor is hot after sitting for 10 minutes. If you remove the cowl it will not do it.

Guess its back to the dealer since I have no clue what else to do myself

Thanks for all the responses and help............will keep the thread updated if i get this figured out

[boscoe99]

Have you checked the fuel cooler to be sure that is it not clogged? Both the water side and the fuel side. Remove hoses as necessary and see if you can blow air freely through first the water side and then the fuel side. On the fuel side I would start at the connection nearest the VST pressure regulator and try to blow air all the way to the point that gasoline would re-enter the VST.

Have you tried removing the hose at the charcoal cannister to see if you can blow air through the hose and then through the vapor shutoff valve? You should not be able to blow air as the valve is normally closed with the motor off.

Have you tried removing the hose from the charcoal cannister to see if you can blow air through the hose that leads to a filter and then the overboard exit fitting? It should be free and clear. Critters are known to crawl into the exit holes to make a home for themselves and their family.

[sthomasIV]

Have you checked the fuel cooler to be sure that is it not clogged? Both the water side and the fuel side. Remove hoses as necessary and see if you can blow air freely through first the water side and then the fuel side. On the fuel side I would start at the connection nearest the VST pressure regulator and try to blow air all the way to the point that gasoline would re-enter the VST.

Have you tried removing the hose at the charcoal cannister to see if you can blow air through the hose and then through the vapor shutoff valve? You should not be able to blow air as the valve is normally closed with the motor off.

Have you tried removing the hose from the charcoal cannister to see if you can blow air through the hose that leads to a filter and then the overboard exit fitting? It should be free and clear. Critters are known to crawl into the exit holes to make a home for themselves and their family.

just checked and all is good!

[sthomasIV]

Some silly questions ..
Have you replaced the secondry fuel filter (69j-24502-00) not the element inside the see thru filter housing, there is another.

Are you running with some sort of cowling protector or hood over the cowling ? material cover ? are the air intakes restricted for what ever reason ? (even very thin gauze type material can really choke a motor)

Have you replaced the ISC valave ?
When you shut down the motor after a good run, do you hear the ISC valve operating and some clicking sounds ?
Have you done a quick test with the ISC valve unplugged ?

what part number is the ISC valve? If i knew which one it was i would try unplugging it next time out or cleaning it. Thanks!

[pstephens46]

Don't know your exact model number.

Guessing part 10 on the link below

2006 and Later F90XA_0112 Yamaha Outboard INTAKE 1 Diagram and Parts

[sthomasIV]

Don't know your exact model number.

Guessing part 10 on the link below

2006 and Later F90XA_0112 Yamaha Outboard INTAKE 1 Diagram and Parts

F90LA. Thats where I am confused. Thought part #10 was vapor shutoff valve? Is it a vapor shutoff valve or an IAC/ISC valve? Either way that is the part I cleaned and tried unplugging today and either way it didn't help my issue. Guess it could be bad but i don't know how to test it

[panasonic]

I would like to know a "possible" explanation why this don't happen with the cowl off?

Does the engine breath easier with it off, so if there is a rich fuel problem it going to get more air and start?

Or is it a heat problem, with the cowl off a temp sensor is reading different?

I find it very strange that it starts every time with that cowl off.

[sthomasIV]

I would like to know a "possible" explanation why this don't happen with the cowl off?

Does the engine breath easier with it off, so if there is a rich fuel problem it going to get more air and start?

Or is it a heat problem, with the cowl off a temp sensor is reading different?

I find it very strange that it starts every time with that cowl off.

Wish I knew the answer to that as well.............All I know is this issue doesn't happen in the winter but come summer time or hot weather it starts again (3 summers now since I bought it new). My last 2007 f90 did not do this at all so i know its not normal. I believe it is a rich fuel problem because pumping the bulb makes it worse to get started and stay running. If you remove the cowl it will never do it.............but its not fun running around in a boat without the cowl on trying to keep water from backwashing in. Heard that was the reason Yamaha painted the SHO 150/175 silver on top to help with the heat issue. All I know is when the cowl is off its perfect like it is in cool weather................That thing gets hot too............When i went to put the cowl back on today from testing it was so hot i could hardly touch it just sitting on the back deck not on the engine. My best guess is with cowl off it allows the gas fumes to vent easier and not cause the problem.

[99yam40]

I believe Yamaha recommended idling for a little bit before shutting down the motor to cool it off some from a hard run, do you do this?

as others have said have you tried opening the throttle a little to see if that helps?

could it be exhaust under the cowling without enough O2 that is causing this?

[sthomasIV]

I believe Yamaha recommended idling for a little bit before shutting down the motor to cool it off some from a hard run, do you do this?

as others have said have you tried opening the throttle a little to see if that helps?

could it be exhaust under the cowling without enough O2 that is causing this?

Yes i let it idle before shutting down. Makes no difference. Still does it if i do or dont.

Tried giving it gas in neutral twice today with same results. Motor reved real high and then shut off

Not sure what is causing this issue.