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F90 Yamaha unpredictable starting
My four-stroke Yamaha 90 (bought new in 2005) has quit running while under power (on step), and then won't start again two times in the past two years. The first time it quit abruptly, and when I tried starting it the starter turned over just fine, but motor would never start even though occassionally it would fire off for less than a second and not continue. While I was waiting to get towed back to town I hooked up a fresh battery and tried to start it again, but that did not work. I checked all the obvious things like the kill switch and for bad gas. Good gas was getting all the way to the vapor separator, but when I checked the pressure in the rail leading to the injectors there was not any pressure. There was some sediment in the bottom of the vapor seperator, and I assumed at the time that I was suffering the effects of some bad gas that had gotten into the engine and clogged the injectors a year previous (I had to have the injectors replaced). This was at the end of the boating season, and since we live above the Arctic Circle, the low temps and lack of a place to work inside, made continued trouble shooting unpractical.
The next spring when I hooked up the hose and tried starting it again, to my surprise, it started immediately, but then when I tried starting it again later that day to warm it up for an oil change, it would not start again. Assuming the problem was the vapor seperator since the rail did not have pressure, I took it out and inspected it. The float was showing some wear and there was a fine whitish powdery substance lining the float chamber. I replaced the float, the needle (even though I could not see that it was worn or misshapen), the filter leading into electronic fuel pump, and gaskets. Checked the electronic fuel pump inside the vapor seperator for continuity (200 ohms on the multimeter's 2000 setting) as well as the voltage (12volts or better) of the leads coming into it. I also cleaned everything and made sure the float measurments were as the service manual said they should be. After this the engine ran without even a hick-up for a little over a full boating season.
Then recently while on step the engine started intermittently stuggling, in rough conditions, at which point I throttled back and came off step, and checked to make sure I was not having gas problems. I turned back for town at low speed and would occassionally throttle up to get on step, at which point the engine would nearly cut-out each time. I tried throttling up one last time just outside the entrance to the harbor at which point the engine completely cut-out and would not start again. The starter turned over fine, but engine would not start. Again, gas was getting all the way to the vapor seperator.
There was no sign of any sort of gas problem and the kill switch was in place. I did not have the gauge and adaptor I needed to check the fuel pressure in the rail leading to the injectors this time, but when I disconnected the quick connector leading into the rail and turned the motor no fuel came from the hose coming from the vapor separator. I again pulled the vapor seperator and inspected it and found it to be in excellent condition, and the float measurments were all as they should be. After reassembling and priming the bulb the motor started right up, but I don't know why. Even worse I have not "fixed" anything so I assume it is only a matter of time before it quits on me again.
Having an unreliable outboard is a huge issue here because of remoteness, and our often marginal boating conditions. Anyone have any ideas about what my outboard's underlying problem might be, or any other suggestions? Our town is accessible only by air and by seasonal barges from Anchorage and Seattle so getting an outboard to a service center would be VERY expensive.
Also, does anyone know of a way to clean my old clogged injectors so I can have them as backups?
Thanks in for taking the time to read my post, and thanks in advance for replying.
The next spring when I hooked up the hose and tried starting it again, to my surprise, it started immediately, but then when I tried starting it again later that day to warm it up for an oil change, it would not start again. Assuming the problem was the vapor seperator since the rail did not have pressure, I took it out and inspected it. The float was showing some wear and there was a fine whitish powdery substance lining the float chamber. I replaced the float, the needle (even though I could not see that it was worn or misshapen), the filter leading into electronic fuel pump, and gaskets. Checked the electronic fuel pump inside the vapor seperator for continuity (200 ohms on the multimeter's 2000 setting) as well as the voltage (12volts or better) of the leads coming into it. I also cleaned everything and made sure the float measurments were as the service manual said they should be. After this the engine ran without even a hick-up for a little over a full boating season.
Then recently while on step the engine started intermittently stuggling, in rough conditions, at which point I throttled back and came off step, and checked to make sure I was not having gas problems. I turned back for town at low speed and would occassionally throttle up to get on step, at which point the engine would nearly cut-out each time. I tried throttling up one last time just outside the entrance to the harbor at which point the engine completely cut-out and would not start again. The starter turned over fine, but engine would not start. Again, gas was getting all the way to the vapor seperator.
There was no sign of any sort of gas problem and the kill switch was in place. I did not have the gauge and adaptor I needed to check the fuel pressure in the rail leading to the injectors this time, but when I disconnected the quick connector leading into the rail and turned the motor no fuel came from the hose coming from the vapor separator. I again pulled the vapor seperator and inspected it and found it to be in excellent condition, and the float measurments were all as they should be. After reassembling and priming the bulb the motor started right up, but I don't know why. Even worse I have not "fixed" anything so I assume it is only a matter of time before it quits on me again.
Having an unreliable outboard is a huge issue here because of remoteness, and our often marginal boating conditions. Anyone have any ideas about what my outboard's underlying problem might be, or any other suggestions? Our town is accessible only by air and by seasonal barges from Anchorage and Seattle so getting an outboard to a service center would be VERY expensive.
Also, does anyone know of a way to clean my old clogged injectors so I can have them as backups?
Thanks in for taking the time to read my post, and thanks in advance for replying.
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