One of the fuel tanks was running low so I switched it over to the main tank. Both motors ran fine for a hour or so than starboard motor ran out of fuel. I switched it back to aux, ran fine the rest of the day. The main tank was full. This was two weeks ago. Took it out today same issue. All the filters are new as are the low pressure pumps. The motor is spitting also. So the starboard motor will only run on the Aux tank??? Any ideas ?? Is there a filter in the tank??? Could it be sucking air??? The boat has had all fuel lines changed out with in the past couple of years??? Which would be more reliable relying on NOAA for the weather or flipping a coin--- heads for calm winds tails for gusty conditions??
ox66 trouble shooting
- Thread starter GreatWhite23
- Start date
I'm unsure what "spitting" means.
So the port engine is good on either tank, but the stbd tank is only good on the aux? This eliminates everything from where the the stbd fuel line from each tank comes together and to the engine. The problem is from that union back to tank. Could be a failing fuel line - either externally or internally. Could be a problem with the pickup tube in the fuel tank. You could narrow things down even further by swapping the fuel lines at the tank. If the problem stays with the stbd engine, then the problem is the line. If the problem goes to the port engine, then the problem is the pickup. You can remove the pickup tube and check it and the screen/sock/whatever you want to call it at the bottom of the tube.
So the port engine is good on either tank, but the stbd tank is only good on the aux? This eliminates everything from where the the stbd fuel line from each tank comes together and to the engine. The problem is from that union back to tank. Could be a failing fuel line - either externally or internally. Could be a problem with the pickup tube in the fuel tank. You could narrow things down even further by swapping the fuel lines at the tank. If the problem stays with the stbd engine, then the problem is the line. If the problem goes to the port engine, then the problem is the pickup. You can remove the pickup tube and check it and the screen/sock/whatever you want to call it at the bottom of the tube.
Thanks for your help. By Spitting it is the back fire they seem to do. I shall mess with it next time I am at the boat. I hopefully am going to take her out Thanksgiving week weather permiting (Tuna/Wahoo). Then home she goes for a overhaul. I am going to redo interior, repaint motors, Wax ect, do some maintenance then off she goes into storage awaiting Spring.
Are you saying this backfiring is a normal thing for these engines? I haven't noticed mine doing any type of backfiring. It runs rough and loud when it's on a hose, but once it's in the water and has the backpressure of the water on the exhaust, it smooths right out and is a surprisingly quiet engine (as far as 2-cycles go).
They starboard motor has always back fired with in five seconds of running at idle. Sometimes stalling the motor. Once in gear they run smoothly. (given alittle throttle) Thinking it could be sucking air. O2 sensor is clean, good plugs, new low pressure pumps. The starboard motor has 1300 hrs the port has 60 sense new powerhead. I am hoping once I replace the gas lines and clean the pick up she will run smoothly. Any thoughts???
If the idle is low ( spec is about 700+ revs) the motors may backfire and shudder especially when the air is colder. Bad low pressure fuel pumps can cause a similar issue.GreatWhite23 said:
I'm not an expert on this, but if it were sucking air at idle, wouldn't it continue to suck air and therefore have running issues, too?
As said above, it sounds like the idle is low. If memory serves, mine idles right around that 700 mark, too.
As said above, it sounds like the idle is low. If memory serves, mine idles right around that 700 mark, too.
GreatWhite23 said:
You need to warm up the motor and then adjust the idle speed screw to get to 700 and a bit at idle. It could be that simple or it could be more complicated like a temp sensor or TPS. I have had your same issue on and off for 3 or 4 seasons. Adjusting the idle has helped but not 100%. If you start and notice the idle lowering, use the shift override button on the throttle and increase throttle to maintain 700 or better until the motor warms up a bit. Once mine had warmed up, the problem went away.
I am not sure why this motor idles low when cold. I thought that one of the air temp or water temp sensors was bad but everything tested OK. Replacing the LP pumps didn't really help. Fuel rail pressure is in spec too. It could be sticky injectors. I have never had them cleaned or tested. Each season I check the color and condition of the old plugs before replacing and I have not noticed any signs of rich or lean fuel mix.
GreatWhite23 said:
A clean O2 sensor does not mean anything. You need a test harness ($25) and a DMM to check it to make sure it is operating properly.
fishbust said:
Funny thing about the O2 sensor. There are two parts to it, the oxygen sensor and the heater coil.O2 sensors need to be hot to work correctly so when it is cold a built-in heater runs to warm it up. Most test done check the sensor but not the heater. On more modern engines, the ECU will post an alarm if the heater coil looks open but not the early SX motors.
Now if the sensor is clogged ( but still electrically working) the more will run rich. At speed than can lead to fouling but when a cold motor is idling it actually can help. My experience is that the O2 does not have in most cases a profound effect on idling. Of course in the rare cases when the sensor portion of the O2 sensor is disconnected or open, the motor can run lean. Under load that can lead to detonation and possible serious damage. You can check the heater coil using an ohmmeter and you can check the sensor section using a digital volt meter and a flame.
Regardless, if the idle is in the 500 to 600 range, the SX motors will shutter, backfire and often stall.
i know zero about these engines, but sneezing usually means the engine is running lean, and sneezing and low idle without other symptoms in gear or at higher rpm in an efi engine would make me think a dirty injector is blocking the spray pattern. if you had an air leak i'd expect a rough idle in gear.
at 1300 hours cleaning the injectors is not a bad idea anyway, so you have nothing to lose.
at 1300 hours cleaning the injectors is not a bad idea anyway, so you have nothing to lose.
That is possible and I would like to hear back if anyone has tried just cleaning the injectors to solve this specific issue with SX motors. Unfortunately, often the mechanic or 'mechanic' ends up doing many things and it is impossible to know what changed whatsuzukidave said:
With respect to this model motor, I would guess that if you took a perfectly OK running one and lowered the idle to 500 to 600 it would shudder and 'sneeze'.
I don't care for the flame test. Personally, I like the DMM better because it shows specifically how the O2 sensor is behaving with the engine running.
Both of my OX's ran bad/idled bad (to me) but yet passed a survey with flying colors, somehow.
1 O2 sensor was totally clogged beyond belief and even had to drill out the draw tube to clear that. The other was clear, just dirty. I cleaned out both with combustion cleaner and seafoam, reinstalled and tested them. Both sat at a fairly steady .7 VDC at idle = both were bad. They need to be jumping around rapidly at idle.
I replaced both (tested again and passed) and immediately noticed a great improvement, motors (and me) were happy. If those sensors are not right, the motors will never be right. My point is folks cannot just clean them and call it good. They need to be tested/verified working properly.
Both of my OX's ran bad/idled bad (to me) but yet passed a survey with flying colors, somehow.
1 O2 sensor was totally clogged beyond belief and even had to drill out the draw tube to clear that. The other was clear, just dirty. I cleaned out both with combustion cleaner and seafoam, reinstalled and tested them. Both sat at a fairly steady .7 VDC at idle = both were bad. They need to be jumping around rapidly at idle.
I replaced both (tested again and passed) and immediately noticed a great improvement, motors (and me) were happy. If those sensors are not right, the motors will never be right. My point is folks cannot just clean them and call it good. They need to be tested/verified working properly.
if this was a car i would doubt it is the o2 sensor given the symptoms are at idle.
on the other, it's probably worth replacing them anyway. if it was a car i'd do it. the ox66 is a cruder efi system than in a car. it looks like it has no air flow sensor so it estimates air flow from rpm and depends exclusively on the o2 sensor for real world feedback. if i have that right, you want the o2 sensor running well.
it is common for o2 sensors on high mileage cars to be "bad" to the point of causing fuel consumption issues or rough running without throwing a check engine code. the ecu throws a code when it sees excessive variation in voltage readings from an o2 sensor but it's not very sensitive because a fair bit of variation is normal and it cannot necessarily spot sensor degradation. i suspect the ox66 ecu allows more tolerance than a car for a bad o2 sensor given the extreme operating conditions.
on the other, it's probably worth replacing them anyway. if it was a car i'd do it. the ox66 is a cruder efi system than in a car. it looks like it has no air flow sensor so it estimates air flow from rpm and depends exclusively on the o2 sensor for real world feedback. if i have that right, you want the o2 sensor running well.
it is common for o2 sensors on high mileage cars to be "bad" to the point of causing fuel consumption issues or rough running without throwing a check engine code. the ecu throws a code when it sees excessive variation in voltage readings from an o2 sensor but it's not very sensitive because a fair bit of variation is normal and it cannot necessarily spot sensor degradation. i suspect the ox66 ecu allows more tolerance than a car for a bad o2 sensor given the extreme operating conditions.
I did replace the O2 sensor off a extra motor I bought for parts Thew I never tested it. The sensor was very clean. I will have them tested. I was thinking off replacing the injectors this winter as well. Not related to this issue but just as a safe guard do to the age.
Don't replace your injectors. They're quite expensive (at least the ones on my engine) to just replace for no reason. However, a GREAT thing to do is to send them out to get cleaned and reconditioned.
definitely. most large towns will have an injector cleaning shop that will do it for about $20 an injector. i would think it would be an easy diy to remove injectors off any outboard, but you will need a manual or an internet search to see how.