Carb fuel drain

Did the first flight on my new-to-me RV-4 yesterday. No squawks in the air. She flies beautiful. During preflight, I found that one of the wing tank fuel drains is sticky. I'll be replacing that soon. Also, I went to drain fuel from the carb and nothing came out. I turned on the boost pump for a few seconds, checked it again, and only got a very small amount. Is that normal for the design?

CARB or Gascolator?

My -4 (like most) has a gascolator on firewall. It wont drain much of anything unless boost pump is RUNNING, or tail is up on a stand.. It is common for the wing sumps to drip/leak if not used much. When I sump my wings, I usually grab the plunger and rotate back and forth to make sure it seats.

Not normal. The bowl should drain the contents readily without the pump on and with the pump on it should gush out.

If you flew without any issues, you obviously have fuel pressure but I would verify that the engine driven pump and boost pump are giving adequate pressure. Your carb drain mght be stopped up. You can remove the fuel line going into the carb and that should drain the bowl. Mine also had a screen inside the inlet.

wilddog said:

Not normal. The bowl should drain the contents readily without the pump on and with the pump on it should gush out.

Click to expand...

Not true in my case. The gascolator on a taildragger is more or less at the same level as the fuel tanks. I don't get much, if any, fuel flow out of the gascolator unless the pump is on.

I rarely get more than a dribble out of mine. It's hard to check as well because of where it is at.
X

Carb drain

Did I miss something? The op said the carb drain not the gascolator...when you pull that float bowl plug it should drain the fuel without the boost pump on or lifting the tail.

Cm

Sorry, I wasn't clear. I meant the gascolator drain for preflight... checking for water.

Fuel Drain

I also have problems with the fuel drains, they stick sometimes. As far as the draining of fuel from the gascolator there is no problem. With the fuel pump on it comes out really fast.

While on this subject..

A couple years ago, I witnessed a Lancair depart our airport, steep climb and engine failure at about 1K AGL, He managed the "the turn" but landed at a high rate of speed and went off runway destroying the plane..he didnt get hurt. He wasnt the builder, and regularly sumped his tanks..the gascolator had no external access, and could only be serviced when cowl off. We pulled it and it was full to the top with water. Plane ran fine as long as attitude was normal, but the steep climb likely got the water flowing...from that day on, I became a fan of checking mine more often..but I have to run the boost pump while doing so.

Wing sumps

FlyFastJP said:

Did the first flight on my new-to-me RV-4 yesterday. No squawks in the air. She flies beautiful. During preflight, I found that one of the wing tank fuel drains is sticky. I'll be replacing that soon. Also, I went to drain fuel from the carb and nothing came out. I turned on the boost pump for a few seconds, checked it again, and only got a very small amount. Is that normal for the design?

Click to expand...

Hey,
Fixinflyinguy is the champ and expert on most things RV, especially-4.

I had similar issue when I noticed one tank sump tinkling post fuel check.

I severely chided her for wetting inside the hanger, then went about fixing her.
Dick Koehler (EAA video guy) has a nice "how-to" video-search him then Curtis Drain repair

The Curtis drains are not field-repairable. They are pretty cheap.
I bought new ones (x2) from Aircraft spruce.
1 for the fix
1 for the traveling tool box= spare

I was apprehensive about the change, concerned that once removed, she would be loose her whole load.

Fear NOT.

I had the new one ready and swapped them in about 10 seconds, and only lost about 2 shots of gas.

My guru suggested I use a thread sealer- Locktite 567.
He says "one small tube =a lifetime supply"

Once the offending part was in my hand a close examination revealed a small tree leaf section, perhaps 1/16" square that must have blown in during a refuel on a windy day. It was caught between the o-ring and the spring.

I'm sure it is still a good "spare".

Daddyman

oh yea

fixnflyguy said:

A couple years ago, I witnessed a Lancair depart our airport, steep climb and engine failure at about 1K AGL, He managed the "the turn" but landed at a high rate of speed and went off runway destroying the plane..he didnt get hurt. He wasnt the builder, and regularly sumped his tanks..the gascolator had no external access, and could only be serviced when cowl off. We pulled it and it was full to the top with water. Plane ran fine as long as attitude was normal, but the steep climb likely got the water flowing...from that day on, I became a fan of checking mine more often..but I have to run the boost pump while doing so.

Click to expand...

Not if it is a carb or a fuel injected model.

Mine has 2 pumps and the location (per plans) does not often fill without boost pressure.
I do check for water.
The same video -EAA -Dick Koehler has significant comment on how to remove, clean , replace it if needed.

Daddyman