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RV6 carburetor fuel leak

jmvolpp

Member
A fuel drip from the drain hole at bottom of the air filter cover looks like it may lead to a carburetor overhaul/exchange - the MS carb is at least 16 years since its last overhaul and a failed float is suspected. Question is, is it imperative to seal the small gaps in the holes (around bottom of accelerator pump and drain plug) in the cover plate bolted to the bottom of the carb? It's readily apparent that even "fuel resistant" sealant is no match for aviation fuel.

Happy Holidays to all!

Mike V
 
"A fuel drip from the drain hole at bottom of the air filter cover"
Do you prime the engine before starting? If so, how much? If over primed, it is common to have fuel drip out of the filter housing drain hole, it would drain back thru the intake & down thru the carb resulting in a messy puddle of fuel in the bottom of the filter housing.

"Question is, is it imperative to seal the small gaps in the holes (around bottom of accelerator pump and drain plug) in the cover plate bolted to the bottom of the carb?"
I assume this is a different issue, unless there is fuel leaking out the sides of the carb in which case a carb overhaul would be warranted.
The seal described is necessary to keep dust & dirt out of the engine, a bit of periodic maintenance in re-sealing it is in order. If the top outside of the filter housing is wet with fuel, yes it's time to re-seal the carb with an overhaul.

"failed float is suspected"
With this would come obvious operational problems, like over rich operation, run on, hard starting & other possible undesirable symptoms... least of your worries would be leaks.

Good luck with your search for solutions.
 
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The fuel drip discovery followed oil and filter change. I didn't notice any indication of fuel drip from the cover until it was time to leak check the screen and new filter. There was no leakage through the gasket between the throttle body and bowl and I couldn't readily see otherwise where it was coming from, so shut the fuel off and drained the gascolator, which seemed to stop what little flow there was. By then it was suppertime, and I let everything sit until the following afternoon when I could take the cover off and look further. The next day, with no indication of further fuel dripping, I ran the engine briefly for leak check, then removed the (dry) cover for a look-see. That being unproductive, and hoping it had somehow healed itself overnight, I cleaned the remnants of old RTV from the aforementioned gaps in the cover plate and resealed with Permatex fuel resistant Orange. Having left the fuel on during this entire time, there was no visible fuel leak down the venturi. Being suppertime again, I left the sealant to cure until the next afternoon. By then the drip had managed to re-establish itself, which brought me to my original question.
I agree that keeping dust out of the intake air, as much as possible, is desirable, but then so it is for remnants of sealant. Whoever last applied sealant had employed the "if a little is good, a lot is better" method, so there was plenty of the fuel degraded stuff dangling in the airstream. While I reapplied just enough sealant to do the job, I'm not fully convinced that the "fuel resistant" label is all it's cracked up to be. The gaps are few and small, so it's a matter of which is least harmful to enter the intake air flow, dust or a glob of RTV?
The fuel drip was very slow, not enough for a messy puddle in the air filter cover nor for any of the operational symptoms described. If it turns out to be a float issue, perhaps it hasn't yet reached that stage.
 
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