2014 15 hp pull-start won't start when cold

[alextompkins]

* EDIT -- manufacturing date is 2009, model number F15CMLH*
I've had this issue since I bought the motor new a few years ago. The engine NEVER starts on the first pull despite the fuel bulb being primed. When it's cold outside, like getting into the 30's, I have to pull the string literally a hundred times before it starts, but it immediately dies. After I do this another dozen times, it finally stays on and eventually warms up. Once warm, and I shut the motor off, it'll start up on the first pull. But if I leave the motor off for a couple hours and let it cool down, it's back to pulling the string a hundred times. Similar issues in the heat of summer, but it'll only take a few pulls to get it started instead of a hundred.

I've cleaned the carb, used fresh ethanol-free fuel, verified there are no air leaks in the fuel line, opened gas tank to make sure it's not making a vacuum in tank, all to no avail. This motor gets ran at least once a week or more and I run the carb dry after every single trip. I've also tried not running the carb dry and get the same problem. I live in south Texas so it doesn't get cold often, but when it does, I can't go hunting, which is painful. One thing I noticed was that the air filter on the intake is greasy, not sure what that could mean. I imagine this all has something to do with the prime start electric choke system. Any help would be greatly appreciated.

[99yam40]

always post the complete model # of your motor when asking question, so everyone know what it is

are you sure it has prime start system and not a choke?

[alextompkins]

My apologies. Model is F15CMLH. Manufacturing date was actually 2009.

[99yam40]

looking at the parts break down of the carb it shows a part they call starter plunger.
not sure if it will help or not, but try operating the throttle a few times to see if that will get a little more fuel into it for cold starts.
Kind of like the old cars with accelerator pumps in the carbs.
will not hurt to give it a try

[alextompkins]

I've tried this as well. Before attempting to start I twisted throttle 3-5 times, twisted back to idle, pulled string many times and nothing. Also tried twisting throttle to deliver more fuel prior to pulling string as mentioned in owners manual when cold starting, and nothing. The more I dig, it sounds like other owners of this motor have had similar problems with cold starting.

[boscoe99]

That motor has Primestart. No choke.

I presume that the carburetor is being completely refilled by pumping the primer ball until it is firm prior to each cold start. And that the throttle is in the start position. If this is not working well when in the start position then maybe try to start it with the throttle in the idle position, or even advanced slightly from the start position, just to see if it gets better or stays the same.

When you cleaned the carburetor did you completely dismantle it, including the removal of the idle mixture (aka pilot) screw? If you did not replace the EPA plug you have ready access to the screw. I would start by turning it out another half turn just to see if the situation gets better or if there is no change. Base setting is 3 and 1/8th turns outward from being lightly seated. Given the Yamaha tolerance of + - a 1/2 turn I would try that. Easy and cheap to do.

Another free and easy trick is to pump the throttle quickly several times prior to the cold start. The carburetor on your model has an accelerator pump. This will add some extra gasoline to the motor which is needed particularly when the motor is cold.

Another trick would be to install a pilot (aka idle mixture) jet that is just a tad larger than what the motor came with. Allows more gasoline to flow when it is needed. You might however then have to tweak the idle mixture (aka pilot) screw downward just a tad if the motor runs a bit rich at idle.

One other trick I have seen done is to modify the Primestart assembly. If you take a look at it closely you will see that one part threads into another part. If the two parts are screwed away from each other this can move the needle further away from the needle seat, which might allow a bit more gasoline to flow when the device is cold. Be careful not to break anything.

[boscoe99]

I've tried this as well. Before attempting to start I twisted throttle 3-5 times, twisted back to idle, pulled string many times and nothing. Also tried twisting throttle to deliver more fuel prior to pulling string as mentioned in owners manual when cold starting, and nothing. The more I dig, it sounds like other owners of this motor have had similar problems with cold starting.

For any problem that any one person has had with a motor there will always be someone else that has had the same problem. If you go looking for something on the inner web, chances are that it can be found. Does not mean that your motor is any more problematic than any other motor. Because it is not.

I pity the poor engineer who is given the task of designing a carburetor that will work well at sub zero temperatures all the way to over 110 degrees F.

[boscoe99]

One thing I noticed was that the air filter on the intake is greasy, not sure what that could mean. I imagine this all has something to do with the prime start electric choke system. Any help would be greatly appreciated.

There is no air filter on your motor. I presume you are talking about the air silencer intake box. Greasiness might be indicative of excess crank case blow by which is allowing oil vapors to collect on the intake screen. Kinda strange if so since the crank case vent hose is attached to the intake box just down stream from the screen.

[alextompkins]

I did completely dismantle the carburetor and have access to the idle mixture screw. Tried backing it out a half-turn from 3 and 1/8, with no change. I did however, with the carburetor still attached, take the primestart off of the carburetor, spray carb cleaner into the port in the carb where the needle goes, put it all back together, and the motor started on the first turn, but only stayed on for about 5 seconds, presumable until it burned through all of the carb cleaner. I also noticed that the needle on the primestart appears to stay all the way out when taken out of the carb. Could this be a faulty part? Also, I can't seem to find the threaded piece you're speaking of since I can't access anything inside the primestart part. It's all sealed with no way to get in there.

[boscoe99]

When cold the needle should be retracted. If you apply 12 volts and a ground to the device when it is cold you should see the needle move outward. If the needle is stuck outward then that would be a problem. It is not allowing gasoline to flow.

You might also have an internal restriction that is preventing gasoline from getting to the point where PS will allow it to flow to the engine.

[boscoe99]

[alextompkins]

When cold the needle seems to be all the way out. I can push it back in but it's spring loaded and comes right back out. This has got the be the problem! I guess the wax is no longer intact forcing the needle to always be extended. Now if only the new part wasn't $250! Thanks for all the help.

[boscoe99]

Only 1/4 of a one BOAT unit.

[99yam40]

before you spend money, make sure it is broken.

while you have the unit off the carb .
measure the length of the needle,
hook up 12 volts to it for a few minutes and then re measure to see if changes.

[alextompkins]

Only 1/4 of a one BOAT unit.

Very true! Too bad 1/4 of a BOAT unit is greater than 10% of the cost of the motor!

I'll try taking the whole PS system off and running 12V through it to verify it is broken. It seemed like there was a little bit of waxy residue on the outer shell of the unit. It flaked off and rolled in between my fingers like wax. Not sure how it would escape the housing like that. Thank you both for the speedy responses.