# F115 problems



## TwoKids (Jan 2, 2013)

Don't know much about the 4S yammies but I have a ton of experience with the 150 2S HPDIs. I'll share my experiences with the intermittent surging/loss of RPM problem.

1) 9/10 times surging is related to a clogged VST filter. I'm in the VST typically once a year, 30min job on the HPDI. However getting to the VST on the F115 looks like a pain but doable. Even if the filter looks clean there is usually a fine powder like coating that you will see if you scrape the filter with your nail and blast with an air compressor. You may have some sucess cleaning it but its worth just replacing. You will need the vst filter and vst o'ring to complete the job.

2) 1/10 times surging is caused by failure of the low pressure lift pumps which feed the VST not being able to keep the vst full at high rpm.

3) Cant say enough how helpful the Yamaha manual has been. I recommend getting one. On the HPDI I can check fuel pressures and vaccum #s in certain areas of the fuel system that help me fault isolate to the trouble filter without guessing and throwing money at parts that dont need to be replaced.

Try pumping the ball next time it starts surging. This will assist the lift pumps to keep the vst full. If pumping the ball stops the surging then I'd say the low pressure lift pumps are bad. If it keeps surging it is probably the VST filter.

Good luck bro.


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## blondmonkey777 (Oct 18, 2012)

Thanks about a month ago that was my problem, I had to do the vst clean and also sent off the injectors to get cleaned replaced racor ,fuel filter at engine ,oil change, thermostat, gear lube, water pump and primer bulb ran perfect after that. I think the problem with the hard start after it being run is what I need to figure out because it has steadily got worse from ever few trips to every trip to last time it did it 3 or 4 times. Also after about 5 seconds of trying to restart the warning buzzer will come on. After that wait 5-10 min to try and restart and it will fire right back up. Makes no sense to me


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## TwoKids (Jan 2, 2013)

If there is anyway you can get someone to hook it up to the YDS that may help. Couple easy things to check is the shift position switch on the shift cable linkage under the cowl, bad switch would allow motor to turn over but no spark. If bad it would explain the hard start condition but not the surging. Another would be the clear bowl filter on the side. Sometimes they don't go on easy cause the plastic bowl expands when removed, you think you have it on but you may not and it sucks air. How many threads are showing above the black plastic nut on that filter assy? Last thing is retrace your steps from a month ago, you did a lot of stuff all at once, could be something stupid you missed.


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## cutrunner (Jun 8, 2010)

Have miguel look at it. It sounds like a bad isc. Dont run it anymore. An isc that is going bad can destroy the ecm and other things. Just did one where the isc killed the ecm and fuel pump. It wasn't cheap... the 115's are kinda k now for isc problems


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## cutrunner (Jun 8, 2010)

> If there is anyway you can get someone to hook it up to the YDS that may help.  Couple easy things to check is the shift position switch on the shift cable linkage under the cowl, bad switch would allow motor to turn over but no spark. If bad it would explain the hard start condition but not the surging. Another would be the clear bowl filter on the side. Sometimes they don't go on easy cause the plastic bowl expands when removed, you think you have it on but you may not and it sucks air. How many threads are showing above the black plastic nut on that filter assy? Last thing is retrace your steps from a month ago, you did a lot of stuff all at once, could be something stupid you missed.


Sounds like you've been around before, all very good places to look.
unfortunately yds doesn't show much of anything on f115's. They have a pretty "stupid" computer, if you will.


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## blondmonkey777 (Oct 18, 2012)

> If there is anyway you can get someone to hook it up to the YDS that may help.  Couple easy things to check is the shift position switch on the shift cable linkage under the cowl, bad switch would allow motor to turn over but no spark. If bad it would explain the hard start condition but not the surging. Another would be the clear bowl filter on the side. Sometimes they don't go on easy cause the plastic bowl expands when removed, you think you have it on but you may not and it sucks air. How many threads are showing above the black plastic nut on that filter assy? Last thing is retrace your steps from a month ago, you did a lot of stuff all at once, could be something stupid you missed.


Thank for the tip, I don't know anyone with yds software or cable, I checked the shift switch and it works as it should, the clear plastic bowl on the fuel filter goes on pretty easy and the o ring in good condition. All of that work I did was at 170 hours, so it's had almost 30 hours of no problems. Pulled the vst filter earlier and was very clean might of had 3 specs in the filter and cleaned it with some carb cleaner. Still lost


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## blondmonkey777 (Oct 18, 2012)

> Have miguel look at it. It sounds like a bad isc. Dont run it anymore. An isc that is going bad can destroy the ecm and other things. Just did one where the isc killed the ecm and fuel pump. It wasn't cheap... the 115's are kinda k now for isc problems


Miguel said he will not work on anything anymore that doesn't have a HB on it...... Hahah he went to the dark side.


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## Creek Runner (Sep 1, 2011)

> > Have miguel look at it. It sounds like a bad isc. Dont run it anymore. An isc that is going bad can destroy the ecm and other things. Just did one where the isc killed the ecm and fuel pump. It wasn't cheap... the 115's are kinda k now for isc problems
> 
> 
> Miguel said he will not work on anything anymore that doesn't have a HB on it...... Hahah he went to the dark side.


That's right biotch, lmao! No I'm not a HB snob! 

No the problem is there isn't a 100% test for the ISC valve. The YDS will only show the signal voltage sent to the ISC doesn't show weather or not the ISC did what it was suppose to do. The ISC doesn't talk back to the ECM. Unless Cut knows a tick that I don't which is totally possible as the F115 isn't a motor i work on very often at all. Maybe 3 in the last 4 years. 

Also in my experience a bad ISC will cause the motor to have an irregular idle at times.  However having to advance the throttle to get her to start is a sign of the ISC going bad.  

Cut Shadowcast777 has my # if he wants my help, I don't even charge him, lol!


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## cutrunner (Jun 8, 2010)

Yea I got a trick for testing isc. Lol swap it with a good one!
If it doesn't make the clicking noise when the key gets turned on its bad. 
Yea I work on about 3 a year as well


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## Creek Runner (Sep 1, 2011)

> Yea I got a trick for testing isc. Lol swap it with a good one!
> If it doesn't make the clicking noise when the key gets turned on its bad.
> Yea I work on about 3 a year as well


Haha, we were texting and I asked him know anybody who has an F115 you can switch it our with. Lol only way to be positive its bad that I know.


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## blondmonkey777 (Oct 18, 2012)

Problem is fixed! I forgot to fill my blinker fluid when I was greasing my muffler sprocket last time.....haha jk thanks for all the help y'all now I just have to convince my buddy with a 2003 f115 that I need to take a part off his engine to see if mine works lol


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