Lots of fuel leaking below air intake on lower front cowl

drskyking · Post by **drskyking** » Fri May 04, 2007 23:30

after recent major overhaul and carb rebuild. Now have 27 hours on my rebuilt engine and carb. After about 20 hrs seems like a lot more of the greenish blue liquid dripping down bottom of air intake duct. Has always dripped a little but lately seems to be more. Can't really tell where it coming from, rear-top and entire bottom of the air intake seem to be wet, dry around seal from carb to air intake duct on front and side. Burning about 3.9 gph. Any comments if this is normal or suggestions as to cause, engine starts and runs great.

Thanks.

Captgrumps · Post by **Captgrumps** » Fri May 04, 2007 23:55

Sounds like the needle in your carbureator is not seating properly. Try shutting the fuel off to see it it stops. Could be trash or the needle was not seated properly at overhaul with the proper head pressure.

Doug

Mikek · Post by **Mikek** » Sat May 05, 2007 06:05

Grumps wrote:Sounds like the needle in your carbureator is not seating properly. Try shutting the fuel off to see it it stops. Could be trash or the needle was not seated properly at overhaul with the proper head pressure.

Doug

I agree 99.99%

Mikek

Post by **joea** » Sat May 05, 2007 09:42

Had the same thing on mine from time to time. I just shut the fuel off.

Nathan K. Hammond · Post by **Nathan K. Hammond** » Sat May 05, 2007 15:38

Ditto.

FYI: The green-ish/blue liquid is the coloring/dye left over from the evaporated fuel. Carefull because it will stain what ever it lands on. (Another one of those "been there, done that..." moments)

nkh

MikeB · Post by **MikeB** » Sat May 05, 2007 17:02

Joe,
What did you figure out with the lean or 'flat spot' on your Chief?

Mike Berg

drskyking · Post by **drskyking** » Sat May 05, 2007 17:09

I forgot to say that it only happens when engine running..Seems dripping out of the low speed mixture screw.

Ron Babos · Post by **Ron Babos** » Sun May 06, 2007 15:41

drskyking: I can't see it leaking out of the idle mixture screw because it's under vacume when engine is running. If the engine is belching smoke, running like it has a full race cam in it and slow to accellerate off the idle the needle is leaking at an extreme rate. Fuel will puddle at the back of the carb heat box and then drip into the lower cowling. It could be junk stuck at the needle not allowing to seal. If you have access to an air compressor, remove the fuel line, and this is important........ remove the drain plug on the bottom of the carb. Failure to do this will cave the floats in due to a pressure build up in the bowl. Give it a good healthy blow-out and see if it brings it back to what you were accustomed to .
Ron

MikeB · Post by **MikeB** » Sun May 06, 2007 17:10

I guess the easiest way to check would be to ground run the engine for a short time, shut if off and see for sure where the leak occurs from. Before Ron responded I was scratching my head and trying to think how the fuel could come out the idle (air) screw. Not that it couldn't if the engine was shut off, but not too likely (at least I haven't seen it before). I expect either the needle/seat is not seating properly or you're seeing 'normal' fuel dripping through the intake after the engine is shut down. I say 'normal' because it's a updraft system and some fuel will always run down the intake after the engine is shut down.

Mike Berg

drskyking · Post by **drskyking** » Sun May 06, 2007 22:59

Thanks guys, it only happens in flight. It is a thick greenish blue liquid that seems to be dripping off the mixture screw although maybe it comes from higher up, then drips on the back of the carb heat box, then down the bottom of the carb heat box out the lower cowl then blown back by the prop. It did used to happen before the carb and engine rebuild but seems like a little more now. Is it just plain normal to happen?

Post by **joea** » Mon May 07, 2007 00:01

mikeberg/wi wrote:Joe,
What did you figure out with the lean or 'flat spot' on your Chief?

Mike Berg

Mike,

No I did not. Went back to the hangar and pulled the cowling off. Then took the finger strainer out of the carb, hoping to find it full of varnish or debris and nothing, it was clean as could be.

Was running out of time and had to stop there. I did a flow check on the fuel coming down to the carb and it appears to be good but who knows.

Am out flying now, in Houston today and Tuesday to Atlanta for a few hours then home on Thursday. The 15th head overseas so not sure I will have time to fuss with it while at home but sure wish I could figure it out.

Joe

drskyking · Post by **drskyking** » Mon May 07, 2007 07:07

Reading top of this thread, what do you folks mean by " the needle may not have been seated with the proper head pressure". What is the proper head pressure? Again, is it normal to get some of this leakage, some other owners here say that there is some leakage out of the float chamber, there are some overflow ports or something. I have never seen the whole carb out of the plane so hard to see everything from the sides with the cowling on. Thanks.

Ron Babos · Post by **Ron Babos** » Mon May 07, 2007 16:41

drskyking: Unfortunately the world has accepted the Stromberg as a dribbler. In my world, they shouldn't and don't leak. I've given up trying to convince people otherwise. (Right, Nathan?) For what it's worth, the three Champs at my strip don't leak. One is injected, so he don't count. For the accepted norm the carb will have a slow drip with the engine off and the fuel valve on. (one drip every 5 seconds or so) Once the engine is started, fuel burn is in eccess of this and it's a non issue. Standard proceedure is to turn fuel valve off when not running engine.
Now back to your problem. Since it can't leak at the idle mixture screw when running, it must be leaking at a higher level and travelling down to the screw and dripping off the knob. Look for porosity in the spider, loose primer fitting in the spider, or a bad base gasket.
The mentioned needle and seat leakage will always leak into the throat of the carb and into the heat box. It can also seep between the gasket between the upper and lower carb halves.
Clean the whole area up and ground run it until you can determine the highest point that is wet with fuel or dye. Let us know what you found.
Just noticed your comment on the thick greenish stuff . On some engines due to valve guides, blowby, leaky intake valve or whatever, oil will actually drain back into the intake tubes. It will mix with fuel and produce the substance you mentioned. To stop that annouying slobbering after you shut the engine off, which happens about 5 minutes after, try running it out of fuel before parking it. Since doing this, I've never had to clean up anything afterwards. It's caused from the fuel vapour in the runners condensing back into raw fuel and dripping out of the throat and carb heat box. Seems happen all at once, giving the impression of a major leak. Only lasts a couple of seconds, usually.
Ron

Nathan K. Hammond · Post by **Nathan K. Hammond** » Mon May 07, 2007 22:08

Ron, I'll get to it eventually. Promise

nkh

Ron Babos · Post by **Ron Babos** » Mon May 07, 2007 22:18

Nathan: Cool. I know what it's like for time. Just bought a new Harley softail, and can't seem to find the time to fly much, although I did tonight for a change. I was wondering if maybe I got a bit anal on that thread and you don't love me any more?

Ron