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Old 05-11-2014, 09:01 PM   #1
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Default Air bubbles in my fuel line

Can anybody tell me why there's air bubbles in my fuel lines. my car is an associated rc8.2 with the reedy 121VS. The break in was by the book and I had some good runs then the bubbles.The engine sounds like it's gargling,if that makes sense.
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Old 05-12-2014, 12:49 AM   #2
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Change the fuel tube and check tank output connection for leaks. Also if you have an inline fuel filter fitted (you should have!) check it too for leaks. As a test you can remove the filter and see if the problem still exists if simply changing the fuel tube doesn't fix it.
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Old 05-12-2014, 06:40 AM   #3
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And if none of that works, try a new tank.
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Old 05-12-2014, 09:15 AM   #4
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+1
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Old 06-11-2014, 04:45 AM   #5
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Can air bubbles in the fuel lines be caused by the way a tank is mounted? Have had issues in the past with the KM H-K1 and now similarly the Xray NT1. Yet the same engine and pipe in a HotBodies R10 and no issue.

Curious and appreciate the feedback!

Thanks,
Andrew
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Old 06-11-2014, 03:39 PM   #6
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Couldn't it be because the fuel line between tuned pipe and fuel tank is too short? I heard that if the line is too short, due to the temp, it generates bubbles. Correct me if I'm wrong.
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Old 06-13-2014, 06:42 PM   #7
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I have been running one and a half times the length of the pipe and header as recommended. Also, it is the same bit that was used with the same engine and pipe and manifold from the previous car that had no issues.
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Old 06-16-2014, 12:07 AM   #8
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Use o-ring on Tank mounts to cushion the tank from vibration. And use sealant on fuel hose b/n tank and carb(and fuel filter if used). Also could cause carb not adjusted correct(too rich). It will dissapate when adjusted correctly. Is there actually air inline of Air bubble like fish eggs?
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Old 06-18-2014, 12:31 AM   #9
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Quote:
Originally Posted by Bundy_Bear View Post
I have been running one and a half times the length of the pipe and header as recommended. Also, it is the same bit that was used with the same engine and pipe and manifold from the previous car that had no issues.
I must admit that I had the same issue with my NT1. Get Serpent
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Old 06-18-2014, 01:42 AM   #10
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Easy fix -> Don't buy translucent fuel line!!!

[The pressure line feeds into the tank at the top and the fuel to carby is drawn from the bottom of the tank. For bubbles to form in the fuel inlet tube it has to come from the tank feed, nipple and tubing... Or.... it's a hot carby!!? If the bottom mix is too lean and the carby heats up to beyond that of the boiling point of methanol 65c ( https://www.google.com.au/webhp?sour...nt+of+methanol ) then it could be a backwash of boiling fuel. Since methanol evaporating in the carb will cool it down, try a richer bottom and/or top.

Also something to consider is siphon, as there's not exhaust pressure either the tank may cool and shrink but hey, if it's happy and you're happy a few bubbles wont hurt it, unless there's an air leak and there'd be fuel residue there too.]
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Old 06-30-2014, 11:17 AM   #11
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I like the easy fix but you also have a great description of what's going wrong. I noticed that only the carb side of my fuel line produced bubbles this weekend. I say carb side because I use a fuel filter.

Quote:
Originally Posted by blis View Post
Easy fix -> Don't buy translucent fuel line!!!

[The pressure line feeds into the tank at the top and the fuel to carby is drawn from the bottom of the tank. For bubbles to form in the fuel inlet tube it has to come from the tank feed, nipple and tubing... Or.... it's a hot carby!!? If the bottom mix is too lean and the carby heats up to beyond that of the boiling point of methanol 65c ( https://www.google.com.au/webhp?sour...nt+of+methanol ) then it could be a backwash of boiling fuel. Since methanol evaporating in the carb will cool it down, try a richer bottom and/or top.

Also something to consider is siphon, as there's not exhaust pressure either the tank may cool and shrink but hey, if it's happy and you're happy a few bubbles wont hurt it, unless there's an air leak and there'd be fuel residue there too.]
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