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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › OS91HZ-PS Fuel Tank Bubbles?
04-25-2009 04:57 PM  9 years agoPost 1
rexxigpilot

rrProfessor

Florida

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OK, was flying my 700N with an OS91HZ-PS yesterday and everything was fine until the 6th flight. All of a sudden a tremendous amount of bubbles started to develop in the fuel tank. The bubbles appear to be coming from the end of the clunk. It looked like the fuel pump was operating in reverse, similar to a fisk tank aerator. The engine won't run right as the problem causes a lean condition. I checked the external fuel tubing for leaks and didn't find any. Can anyone shed some light on this problem? Thanks in advance!

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04-25-2009 05:03 PM  9 years agoPost 2
Auto180_OCMA

rrApprentice

Futaba City Z (Mobara)

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Most likely
You can have a little tiny hole in your pickup fuel line inside the tank. I ve been running couple of os 91 hz pd(s) for almost a year never had ny problem with them.

In the seven hundred i have fuel line drop from the pickup into the fuel tank, holes from carbon fiber cutting into the fuel line.

I ve solved all of them by either using the IM fuel fuel line from japan, or BRU line silicone tubeing. And shield the lines with rubber groummet from the carbon.

Make sure you dont have a hole inside the tank from the pickup line.
That is the common problem.

I hope that was some sort of help.

AMA 334000

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04-25-2009 05:53 PM  9 years agoPost 3
rexxigpilot

rrProfessor

Florida

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Auto,

Thanks for the input. Do you think a hole in the pickup fuel line within the tank would cause bubbles to emanate from the clunk? I didn't find any fuel line problems outside the tank. This is frustrating. I really wanted to fly the 700 today and the day is wasting away quickly.

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04-25-2009 05:55 PM  9 years agoPost 4
Auto180_OCMA

rrApprentice

Futaba City Z (Mobara)

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Yes SIR
I have seen it myself. That is where i would start with

AMA 334000

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04-25-2009 09:22 PM  9 years agoPost 5
rexxigpilot

rrProfessor

Florida

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Update - Problem Intermittent
The problem appears to be intermittent. I took the 700 out for a quick flight a bit ago after verifying there was no leaking fuel tubing, including the lines inside the tank. Bubbling was still there until the 3 minute mark of the flight. Then it suddenly disappeared. Now I'm really lost as to what is causing the problem and intermittent problems are almost always the hardest to solve. What should I look at next? Could this be a defective pump? Engine is almost new.

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