Re: Marvel Carb Problem
What good would it do to try to help you if you haft to use a lic mechanic. I'm sure he would need to remove
the carb and inspect it to see what's wrong.
Tom Smith A&P/IA
From: 335dave@... [canard-aviators]
Sent: Fri, Mar 15, 2019 3:43 pm
Subject: [c-a] Marvel Carb Problem
I have a Marvel-Schebler Carb MA-3PA in a Long-EZ with a 0-235L2C. 1650hrs, I've had it for over 1000 of those. The carb was overhauled some time when checking for the venturi AD (single piece or two piece). Apart from the idle cut off never working since electronic ignitions went on (maybe 6-700hrs ago) there have been no issues.
3 days ago at 200' climbing out the engine began to loose power. I had sufficient RPM left to climb a little more and return and land without incident. The engine had stopped before I landed, don't ask me when exactly. There was a pool of fuel under the plane.
Its now in a hangar with the head of maintenance for a small flying school He is very familiar with the engine and carb. They have several C152's. I have to use a licensed person as I didn't build this plane.
When adding fuel to the carb it will not shut off when the float gets to where it should be level. We are testing via an elbow in the fuel/water drain on the side of the carb and a tube pointed vertically. A bit like a sight gauge on a boiler. Whatever we do, with the fuel tuned on and fuel pump going the tube fills slowly gets to around the level of the floats and continues until overflowing. Sometimes it hesitates for a second or so as if the floats are catching on the sides internally and then letting go. In other words the carb will always overflow beyond the level of the floats.
We have, in separate operations, replaced the seat, the needle, the floats, the rectangular spring that is a part of that assembly, the finger screen in the fuel inlet, we have done lots of tapping on the sides of the carb during testing to see what that does. The float height has been set carefully per the manual. Of course I cleaned the inside of the carb thoroughly. There was a small amount of rust but otherwise nothing significant.
Short of replacing the carb we are open to ideas please.
and building LE VH-XEZ