The motor is a 2001 F115 yamaha 4 stroke. EFI
The problem only presents itself under very specific conditions.
You must do a 5-10 minute+ run on the plane(so 3500rpm+) then turn off the engine immediately and wait 7-10 minutes give or take. Under these conditions the motor will not restart. It will simply turn over and over. After a little while longer it will eventually restart. It has never not re-started.
I have done the following in trying to rectify the issue.
Tested fuel pressure at the rail. Read about 40psi. a little less while cranking.
Removed VST and cleaned filter
Removed injectors and cleaned/flow tested (this was done for a different issue)
Adjusted TPS setting (again, this was done for a different issue)
Ran the motor on a different ECU
Attempted to start the motor with a remote harness.
Checked injector pulses using a noid light.
Checked for spark.
Compression's are good.
Played around with the shift switch because I read about a person having similar issues and his was caused by this sensor. I'm still not quite sure what it does.
Primer bulb looks and feels good. Not getting sucked flat for instance.
Today was my first real break though. I discovered if I unplug the thermosensor on the exhaust plate(?) it will start. Then when I quickly plugged it back in,the motor would just turn over. Does anyone know anymore about this sensor? and why it is affecting this motor?
Thanks for your help. If you need more info ill try to elaborate where possible.
Bonus History: motor was recently serviced. First trip out after the service it had water on the bottom plug. Removed the head and found it heavily corroded. 11 welds later it was back on. First trip out after this work was done it had an oil leak. Found the oil pump to be the culprit. A real issue with these early models I learned. Replaced with the superseded pump. Since doing the head the motor has had the warm restart issue as well as a minor vibration at low revs in gear. The latter is why the injectors were tested and the TPS was adjusted. Neither helped. However both were out of spec.
The problem only presents itself under very specific conditions.
You must do a 5-10 minute+ run on the plane(so 3500rpm+) then turn off the engine immediately and wait 7-10 minutes give or take. Under these conditions the motor will not restart. It will simply turn over and over. After a little while longer it will eventually restart. It has never not re-started.
I have done the following in trying to rectify the issue.
Tested fuel pressure at the rail. Read about 40psi. a little less while cranking.
Removed VST and cleaned filter
Removed injectors and cleaned/flow tested (this was done for a different issue)
Adjusted TPS setting (again, this was done for a different issue)
Ran the motor on a different ECU
Attempted to start the motor with a remote harness.
Checked injector pulses using a noid light.
Checked for spark.
Compression's are good.
Played around with the shift switch because I read about a person having similar issues and his was caused by this sensor. I'm still not quite sure what it does.
Primer bulb looks and feels good. Not getting sucked flat for instance.
Today was my first real break though. I discovered if I unplug the thermosensor on the exhaust plate(?) it will start. Then when I quickly plugged it back in,the motor would just turn over. Does anyone know anymore about this sensor? and why it is affecting this motor?
Thanks for your help. If you need more info ill try to elaborate where possible.
Bonus History: motor was recently serviced. First trip out after the service it had water on the bottom plug. Removed the head and found it heavily corroded. 11 welds later it was back on. First trip out after this work was done it had an oil leak. Found the oil pump to be the culprit. A real issue with these early models I learned. Replaced with the superseded pump. Since doing the head the motor has had the warm restart issue as well as a minor vibration at low revs in gear. The latter is why the injectors were tested and the TPS was adjusted. Neither helped. However both were out of spec.
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