[jrvssgl]

I was doing maintenance on My RV today when I noticed something very odd, with the cowls off. I had the boost pump turned on for some other thing I was working on, and I could start to smell avgas from inside the aircraft. Upon examination I noticed fuel running at a fairly good rate out of the FAB. The aircraft has not flown for about two weeks, however flew fine when I parked it. So I shut the fuel pump off and turned it on again, and tapped the carb, and bingo the fuel quit running out. Now I am thinking I should pull the carb and check the float, however i was wondering if you can pull the bowl just by removeing the screws that hold the bowl on or if you have to totally remove and overhaul the carb. Any thoughts or advice is apprecieted.

 

[scard]

This is important stuff, don't take risks. That is a stuck float. Pull it and have it gone through. The alternative is engine stoppage in the air. Not worth it.

 

[Mitch757]

Jarvis,

Volare Carburetors has a Service Bulletin dated March 13, 2009, concerning float clearance. The carb will have to come off since the clearance must be checked with the carburetor on it's side. I'd let a professional do the precision stuff.

While off, you might as well check to see that you have the latest floats (smurf blue in color) to comply with another bulletin (Volare SB-2 and Precision MSA-13).

I attached a copy of the bulletins to an email to you.

Mitch Garner
RV-4 flying

 

[MrNomad]

Fortunately, you discovered this on the ground

Jarvis:

Scott is right. Nothing is worth taking risk in an airplane especially when it deals with such a volatile substance as fuel. It could be a stuck float, but the source of the problem could be further upstream.

A leaky float is not going to mysteriously heal itself after you tap on the carb. Once the float is filled with fluid, the carb will flood no matter how hard you bang on it. Or, the float is hanging up on the sides of the bowl because the float is distorted.

Some dirt that got past a ripped/deteriorated membrane in the gascolator and the carb filter could be keeping the needle valve off its seat allowing gas to pour thru.

My guess would be the float but I would not stop there.

If trash caused the needle to remain off its seat, where did the trash come from? Fuel lines (especially flex lines) deteriorate over time and deposit trash further downstream. If the inline gas filter that sits in the carb was improperly installed, it may not be working, or some of the fine wires that comprise that filter could have broken off causing the needle to NOT return into its seat.

So not only must you take the carb apart, but also all of the systems that feed into the carb. There are some special tools required for carb work so don't just clean it and call it a day.

One of the better places to get carb parts is http://avstardirect.com. I'm sure there are other good vendors, but these folks seemed compenent during the last carb repair we did.

Finally, consider yourself lucky that this problem expressed itself on the ground.

 

[jrvssgl]

Thanks Guys.

The carb is coming off tonight. Will try a few engine shops tommorrow to see if they are capable of doing the overhaul and have the parts.

Thanks again

Jarvis

 

[RV7AV8R]

I agree you need to take it off to inspect. Somewhat related to this issue about 2 months ago I replaced my float per the Service Bulletin. Yesterday I noticed on the rear of the bowl gasket there is blue fuel dye. It is just on the edge of the gasket with no signs of fuel dye running down or anywhere else. This is a tail dragger, is this common since the bowl sits tilted back all the time in the hangar. All the srews on the bowl are still tight with torqu paint still in place.

 

[Jeff Vaughan]

I experienced the same thing after I had reinstalled my carb after the Float SB was completed by Volare carbs. I sent it back to them and they replaced the gasket and float needle. Took about a week.

The carb was leaking without the boost pump on.

 

[N941WR]

Thanks Guys.

The carb is coming off tonight. Will try a few engine shops tommorrow to see if they are capable of doing the overhaul and have the parts.

Thanks again

Jarvis

Don't go to an engine shop, go to a carb shop!

Call AVStar in the morning. They did a great job on my carb and I have heard nothing but positive responses from the people I have sent there.

A full overhaul will cost around $700, including shipping. When you get the carb back, you will check the serial number to make sure it is the same one you sent in. Of course, they do have an exchange program for those of you have more common carbs.