OX66 LP Fuel Pumps
- Thread starter fishinAK1
- Start date
ARRRRGGG! Guess my "feeling" was wrong. Not the O2 sensor! ARRRR
I replaced the LP pumps and the O2 sensor. Started in the bucket. fired right up, idled at 600. then slowly brought up to 2000 then 3400. seemed about normal, until about 5 min of running then began surging. Not huge surges...up to 3800 then down to 3400.... Then I backed back down to 2200. again it would surge up to 2600 and back down to 2200.
During all this, I checked the fuel pressure. seemed to stay around 35 PSI. Although at higher RPMs the gage needle would quickly wiggle between 34-36. Question is is this because all the vibrating shaking from the outboard or is the pressure actually fluctuating that fast? Ill post a video of this.
Im also curious if any of this is due to the fact that this is all running in the bucket, using the idle throttle paddle. Honestly, I rarely run this in a bucket. Maybe it would run differently in the water. Have you noticed motors behave different in a bucket vs running on the water?
I replaced the LP pumps and the O2 sensor. Started in the bucket. fired right up, idled at 600. then slowly brought up to 2000 then 3400. seemed about normal, until about 5 min of running then began surging. Not huge surges...up to 3800 then down to 3400.... Then I backed back down to 2200. again it would surge up to 2600 and back down to 2200.
During all this, I checked the fuel pressure. seemed to stay around 35 PSI. Although at higher RPMs the gage needle would quickly wiggle between 34-36. Question is is this because all the vibrating shaking from the outboard or is the pressure actually fluctuating that fast? Ill post a video of this.
Im also curious if any of this is due to the fact that this is all running in the bucket, using the idle throttle paddle. Honestly, I rarely run this in a bucket. Maybe it would run differently in the water. Have you noticed motors behave different in a bucket vs running on the water?
next step suggestions?
what are the symptoms of a failing TPS? I tested the resistance of it wo ignition. BUT maybe testing the actual volts while running is a better idea. any way to do this without the test wire harness referenced in the manual?
Also I was thinking maybe a temperature thing, since it seems to occur AFTER its been warmed up a bit. But all 6 cylinders seem very similiar temp to the touch. Also the Tstats are new last year.
what are the symptoms of a failing TPS? I tested the resistance of it wo ignition. BUT maybe testing the actual volts while running is a better idea. any way to do this without the test wire harness referenced in the manual?
Also I was thinking maybe a temperature thing, since it seems to occur AFTER its been warmed up a bit. But all 6 cylinders seem very similiar temp to the touch. Also the Tstats are new last year.
At this point, I'd get the Yamaha YDIS diagnostic software, older version, I think 2.0, it lets you check a lot of different things, including TPS voltage. Not that expensive on ebay. I bought software and cable for around $100 and it really comes in handy to read codes, voltages, temps, pressures, etc. while operating at any and all ranges. I used it and solve a surging problem with my F150 related to a TPS out of calibration.
OK the latest...
Instead of running in a bucket, I took it down and dumped her in the bay.
The GOOD:
Again fired right up and actually seemed smoother, idled settled around 8-900. idled out of the harbor and got 'er up on step. again seemed smoother and looking at the fuel flow gage, it was almost right back to what was normal around 12-13 gph cruising at 4100 RPM and 25 knts. This was/is a good sign! better than the 17 gph before the new pumps and O2.
The BAD:
At WOT I was still only able to get about 5000 RPM, used to be about 54-5500.
The UGLY:
After cruising around about 3800 RPM for about 15 minutes, I brought her off step and to begin coming into the harbor. As soon as she came off step the surging started again. surging between 32-36ish rpms every 20 seconds or so. The continued all the way back the way back into the ramp.
But hey NO ALARMS!
So where does that leave me? fuel consumption back to normal, generally seems smoother, gained a few top-end WOT RPMS but still missing top 400, and surging at low rpms AFTER warmed up.
Sure sounds like a plugged VST to me! but I swear I just checked it twice in the last 2 days. and it was clean. Would a plugged RACOR, or on outboard fuel filter cause surging?
AND Im still not ruling out the TPS.
Any and all advice sincerely and greatly appreciated!!
Instead of running in a bucket, I took it down and dumped her in the bay.
The GOOD:
Again fired right up and actually seemed smoother, idled settled around 8-900. idled out of the harbor and got 'er up on step. again seemed smoother and looking at the fuel flow gage, it was almost right back to what was normal around 12-13 gph cruising at 4100 RPM and 25 knts. This was/is a good sign! better than the 17 gph before the new pumps and O2.
The BAD:
At WOT I was still only able to get about 5000 RPM, used to be about 54-5500.
The UGLY:
After cruising around about 3800 RPM for about 15 minutes, I brought her off step and to begin coming into the harbor. As soon as she came off step the surging started again. surging between 32-36ish rpms every 20 seconds or so. The continued all the way back the way back into the ramp.
But hey NO ALARMS!
So where does that leave me? fuel consumption back to normal, generally seems smoother, gained a few top-end WOT RPMS but still missing top 400, and surging at low rpms AFTER warmed up.
Sure sounds like a plugged VST to me! but I swear I just checked it twice in the last 2 days. and it was clean. Would a plugged RACOR, or on outboard fuel filter cause surging?
AND Im still not ruling out the TPS.
Any and all advice sincerely and greatly appreciated!!
Ok. 1 more update for tonight.
I double checked the on outboard fuel filter. Super clean no water.
I again checked the resistance from the TPS. In neural it was 1.4. With linkage to valve #1, ensuring fully closed, Resistance is about .9.
I kept checking and my son slowly pushed the throttle forward. Definitely wasn’t as smooth as I was hoping. At some points the resistance even decreased for a little bit as the throttle was pushed forward. I assume that’s not right?
I also noticed that the resistance will jump around just by me lightly tapping the TPS. Should it be so very sensitive?
The big question I have now is.... I am testing resistance and not actual volts. Which I guess I can’t do since I don’t have the pig-tail harness.
1) Should I expect different results if I were testing voltage?
2)Should I attempt to adjust the TPS? Based on resistance?
3)how does a TPS go bad or out of adjustment? Is it common?
4)is there a way to test voltage WO the special harness?
I double checked the on outboard fuel filter. Super clean no water.
I again checked the resistance from the TPS. In neural it was 1.4. With linkage to valve #1, ensuring fully closed, Resistance is about .9.
I kept checking and my son slowly pushed the throttle forward. Definitely wasn’t as smooth as I was hoping. At some points the resistance even decreased for a little bit as the throttle was pushed forward. I assume that’s not right?
I also noticed that the resistance will jump around just by me lightly tapping the TPS. Should it be so very sensitive?
The big question I have now is.... I am testing resistance and not actual volts. Which I guess I can’t do since I don’t have the pig-tail harness.
1) Should I expect different results if I were testing voltage?
2)Should I attempt to adjust the TPS? Based on resistance?
3)how does a TPS go bad or out of adjustment? Is it common?
4)is there a way to test voltage WO the special harness?
You're right, it does sound like a clogged vst filter. Another possibility that you may as well change are the injector filters. They are inexpensive and will take less than 10 minutes to change. Worth a change as maintenance every few years.
The tps shouldn't change voltage when you tap it. It could be that once it gets hot under the cowling, it begins to malfunction.
The bright side is that once you get done with all of this, you'll practically have a new engine...
The tps shouldn't change voltage when you tap it. It could be that once it gets hot under the cowling, it begins to malfunction.
The bright side is that once you get done with all of this, you'll practically have a new engine...
Thank you Wilton,
The injectors were just cleaned and supposedly recalibrated to spec 3 weeks ago.
Anymore thights on the TPS? I’m at start a TPS thread so folks dont have to read this novel
The injectors were just cleaned and supposedly recalibrated to spec 3 weeks ago.
Anymore thights on the TPS? I’m at start a TPS thread so folks dont have to read this novel
Again, yes it is very sensitive.
Did you decarbon the engine 1st?
I believe these engines have a knock sensor. If the engine was running so rich that everything was carboned over, you could have hot spots on the piston or head. I'll be honest that I dont know what an ox66 will do if it detects knock (btw, one can't always hear knock), but by not decarboning the engine 1st, you might continue to chase this issue.
I can also tell you that when I swapped O2 sensors, the computer seemed to need time to "relearn" before everything was 100%. The fact that your engine is using the right amount of fuel now tells me your O2 was bad.
CORRECTION: only the 3.1 has a knock sensor, the 2.6 does not.
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I did not decarb the engine prior to installing the new O2. I did not want to risk running the engine w an O2 sensor that I strong suspected (and seems like rightly) was bad.
I guess I could (should) do this now?
How long did it take for your computer to "learn" the system after your new O2?
I guess I could (should) do this now?
How long did it take for your computer to "learn" the system after your new O2?
ARG! Im struggling and really at a loss of where to go from here.
Unfortunately, I live in a town only accessible by jet or ferry and dont have may options for outboard shops. The two Yamaha shops in town don't wanna take on my old 2 stroke problems, they're plenty busy with 4 stroke warranty work. And I dont blame them!
Unfortunately, I live in a town only accessible by jet or ferry and dont have may options for outboard shops. The two Yamaha shops in town don't wanna take on my old 2 stroke problems, they're plenty busy with 4 stroke warranty work. And I dont blame them!
My reasoning for running the old O2 and decarboning was because the engine was already running rich, why not put all that fuel to good use with a bunch of seafoam in it! My 2nd thought was why risk contaminating or damaging a new sensor. Doing a shock treatment under load removes a LOT of carbon. Why take the chance.
As for the learning, I would say several operating cycles from full cold to warm. How many minutes or hours, I can't say. Reading the service manual one could conclude that the ox66 system is very much like any automotive system. It runs in open and closed loop modes and will make adjustments based on sensor input.
As for the clogged vst, why would your engine surge throttling down from a clogged filter?
I just ran in the bucket again. Interesting that it didn't start doing the surging until after it warmed up, 10 min or so.
also seemed interesting how oily the bucket water was after 15 minutes. Pic attached
Is this an indication Im running way to rich? Checked the oil rod lingage and am less than a 1/8" from stop...
triple checked VST and filter. Again spotless.
also seemed interesting how oily the bucket water was after 15 minutes. Pic attached
Is this an indication Im running way to rich? Checked the oil rod lingage and am less than a 1/8" from stop...
triple checked VST and filter. Again spotless.
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Toothpick 10
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You know I have been thinking the same thing about possibly bad gas. But i have drained the VST into a jar 4 times now. And it looks good to me, at least no water. And it were bad gas it seems like it would be surging at higher throttle too right?
As far as the injectors, I sent them to Brucato FIS (seems highly recommend in many forums). He said that they were very clean, but yes, all 6 were running rich. One was 6% two were 4% and three were 2%. He said it is very uncommon for all six to be rich... but he was able to recalibrate them all and after retesting they were all at spec. But why were they all running rich in the first place? I think that is the root of our problem.
This afternoon I but the boat in the water again. Ran the same. I was careful to see when the surge occurred 90% of the time it’s between 3000 and 3600 RPMs (surges of 300 rpms). A few mini surges (+100rpms) at less than 3000 and almost no (Only once) surges above 3800 rpms. Seems like a pretty specific throttle position where it’s occurring. But still not surging regularly, at that position.
...It still seems like it could possibly be a TPS issue, to me....
Like a bad resistance spot. Also seems weird that TPS volts was only 3.5 at WOT. Shouldn’t it be 5.0?
thanks again for all the thought you guys are giving this. When we get this figured out I’d really like to send ya something from AK as a Thank you!
As far as the injectors, I sent them to Brucato FIS (seems highly recommend in many forums). He said that they were very clean, but yes, all 6 were running rich. One was 6% two were 4% and three were 2%. He said it is very uncommon for all six to be rich... but he was able to recalibrate them all and after retesting they were all at spec. But why were they all running rich in the first place? I think that is the root of our problem.
This afternoon I but the boat in the water again. Ran the same. I was careful to see when the surge occurred 90% of the time it’s between 3000 and 3600 RPMs (surges of 300 rpms). A few mini surges (+100rpms) at less than 3000 and almost no (Only once) surges above 3800 rpms. Seems like a pretty specific throttle position where it’s occurring. But still not surging regularly, at that position.
...It still seems like it could possibly be a TPS issue, to me....
Like a bad resistance spot. Also seems weird that TPS volts was only 3.5 at WOT. Shouldn’t it be 5.0?
thanks again for all the thought you guys are giving this. When we get this figured out I’d really like to send ya something from AK as a Thank you!
A timing light could be a useful tool. If you could run the motor around 3500 rpm under a load with it hooked up, watch the to see if the timing changes when it surges. If the tps is not working correctly, the timing will fluctuate and mirror the surge. If you try hooking it to each coil wire individually while surging, the light will go out if you have a bad coil. If you also hook up the fuel pressure guage at the same time, watch to see if the fuel pressure mirrors the surge.
Can someone else verify: my understanding is that the O2 sensor is useless at higher RPMs, it is only used for lower rpms. With the LP fuel pumps, take the hoses off and then try and suck and blow in each end you should be able to do one but not the other. I don't think that is the problem for you since you have greater fuel burn. I had one of the two on my HPDI go and the only symptom was that the motor felt like it was cutting out at higher rpms (a mechanic diagnosed it as "losing a coil when it heated up") Actually what was happening was that above 4000, the VST tank was getting sucked dry and the motor was starving for fuel. As soon as I brought the rpms below 4000, the remaining, good, lp pump was able to keep up with demand and refill the vst tank and the motor ran perfectly. The cut out and kick back in was so instantaneous it was like a cylinder (electrical) shut down. Like I said, probably not your problem but when I replaced both, the bad one would allow me to suck air back and the good one wouldn't.