Insane air bubbles in fuel line - RCCanada - Canada Radio Controlled Hobby Forum
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Old 11-20-2011, 04:52 AM   #1
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Question Insane air bubbles in fuel line

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So I haven't run my nitro rustler since last year and after overhauling the engine (looked a bit rusty inside), I went ahead and tried to start it. It started just fine but I'm getting lots of air bubbles in my fuel line and I have no idea what's going on.

I already took of the fuel line, pinched one end, attached a bike pump to the other, and pumped it as hard as I could under water and there were no bubbles coming out anywhere so I'm guessing that's not the problem. Then I took the fuel tank out, filled it with water, covered the fill hole and the pressure return hole, and blew into the fuel out hole to see if it might be sucking air in from the top of the tank; it wasn't and the tank was perfectly sealed.

As far as I can imagine there's no other way I could get air in the fuel line. When I'm priming the engine it works great but as soon as the engine starts I get massive air blobs (about 70% air : 30% fuel) in the line which shut the engine off. The fuel lid does have a very bad seal (I need to hold the lid down while priming) but it's been like that since last year (when it worked fine) and I don't see how that could affect it.
Any ideas?
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Old 11-20-2011, 06:36 AM   #2
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Re: Insane air bubbles in fuel line

If the tank has a primer have a really good look at that. They are prone to air leaks.
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Old 11-20-2011, 07:09 AM   #3
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Re: Insane air bubbles in fuel line

Whats the condition of the rubber mounts for the tank, are they isolated from the frame, because of engine vibration causes fuel foaming hence air bubbles in the fuel lines.
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Old 12-08-2011, 12:09 AM   #4
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Re: Insane air bubbles in fuel line

it sounds like you either have a cracked fuel barb or your primer is leaking air.

Only way to tell is to change the tank..Also if you have to press down on filler lid to seal the tank this is also going to lead to issues in fuel flow.
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Old 12-31-2011, 05:53 PM   #5
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Re: Insane air bubbles in fuel line

hey did you try spraying nitro cleaner into the fuel line while holding the throttle open? .. always works for me when I havnt run my car in a while.
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Old 03-16-2012, 09:12 AM   #6
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Re: Insane air bubbles in fuel line

underwater pressure test was ok... but have to hold the lid down to prime?
certainly sounds like the primer..... and the tank lid o-ring
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