yamafisher767
Cadet
- Joined
- Sep 14, 2009
- Messages
- 6
Ok,
So I have been experiencing an intermittent loss of rpm @WOT (5400 rpm) on my outboard. This problem first started about 2 years ago and was a relatively rare event. I immediately took the boat to a very reputable Yamaha technician who checked the boat six-ways to Sunday in a tank. He was unable to replicate the problem, didn't charge me a dime (thankfully) and said to just wait until it became a consistent problem. Well, at the beginning of this year the problem started to happen more frequently. At this time, I get the behavior on every trip...
The problem is very similar to those previously described... a drop from 5400 to 4800-5100, very immediate, sometimes it will jump back up to 5400 and may hold for 5-10 minutes and then jump back down. I also have noted that my fuel consumption seems higher than usual.
Checked compression, had injectors cleaned and tested, Checked low pressure fuel, VST high pressure fuel (35.5 psi invariant under all conditions, even during the loss of rpm event), Cleaned the O2 sensor, Checked link & synch, checked TPS. observed the O2 sensor output during idle in the water (~0.47V) start to push the throttles up and watch the O2 sensor start to lean-out (down to ~0.3V), approaching WOT and the O2 sensor starts to come back up and stabilize (0.4-0.5V). When the loss of RPM occurs, I can see the O2 sensor quickly start to climb up (0.67-0.7+ Volts). when the rpm comes back online, the O2 responds by heading back to the mid-range again.
Now here's the twist. When I was checking the TPS, I noted a nice smooth voltage output response and a constant 5.0V input. However, I also heard a buzzing sound when I advanced the throttles. It seemed odd, so I relayed this information to a trained Yamaha Mechanic friend who said that I should not be hearing any buzzing and that I must have a short in the TPS, even though I did not see any spikes in the input/output. Furthermore he had seen this before and suggested that I get a TPS. I spent the $100, dropped in the new TPS and guess what... still buzzes! So I look a little further and discover that it is not the TPS that is buzzing, it is the fuel injectors. With the key in the "on" position, motor is NOT running, when I advanced the throttles very slowly I can get to WOT without the injectors going off, but, if I move the throttles at what I would call a normal hole-shot, all 6 injectors will fire simultaneously for a half-second or so,... almost like an accelerator pump! The length of fire seems to vary and the throttle position at which they fire also seems to vary and might even be speed dependent... My mechanic buddy says that the injectors should not fire at all without the motor running and now thinks there is something wrong with the ECU... I am at a loss... any thoughts?
So I have been experiencing an intermittent loss of rpm @WOT (5400 rpm) on my outboard. This problem first started about 2 years ago and was a relatively rare event. I immediately took the boat to a very reputable Yamaha technician who checked the boat six-ways to Sunday in a tank. He was unable to replicate the problem, didn't charge me a dime (thankfully) and said to just wait until it became a consistent problem. Well, at the beginning of this year the problem started to happen more frequently. At this time, I get the behavior on every trip...
The problem is very similar to those previously described... a drop from 5400 to 4800-5100, very immediate, sometimes it will jump back up to 5400 and may hold for 5-10 minutes and then jump back down. I also have noted that my fuel consumption seems higher than usual.
Checked compression, had injectors cleaned and tested, Checked low pressure fuel, VST high pressure fuel (35.5 psi invariant under all conditions, even during the loss of rpm event), Cleaned the O2 sensor, Checked link & synch, checked TPS. observed the O2 sensor output during idle in the water (~0.47V) start to push the throttles up and watch the O2 sensor start to lean-out (down to ~0.3V), approaching WOT and the O2 sensor starts to come back up and stabilize (0.4-0.5V). When the loss of RPM occurs, I can see the O2 sensor quickly start to climb up (0.67-0.7+ Volts). when the rpm comes back online, the O2 responds by heading back to the mid-range again.
Now here's the twist. When I was checking the TPS, I noted a nice smooth voltage output response and a constant 5.0V input. However, I also heard a buzzing sound when I advanced the throttles. It seemed odd, so I relayed this information to a trained Yamaha Mechanic friend who said that I should not be hearing any buzzing and that I must have a short in the TPS, even though I did not see any spikes in the input/output. Furthermore he had seen this before and suggested that I get a TPS. I spent the $100, dropped in the new TPS and guess what... still buzzes! So I look a little further and discover that it is not the TPS that is buzzing, it is the fuel injectors. With the key in the "on" position, motor is NOT running, when I advanced the throttles very slowly I can get to WOT without the injectors going off, but, if I move the throttles at what I would call a normal hole-shot, all 6 injectors will fire simultaneously for a half-second or so,... almost like an accelerator pump! The length of fire seems to vary and the throttle position at which they fire also seems to vary and might even be speed dependent... My mechanic buddy says that the injectors should not fire at all without the motor running and now thinks there is something wrong with the ECU... I am at a loss... any thoughts?