VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 31 Carb problem

My 31 has been starting and running good. Pull choke out some and starts on second try even after sitting for a month.

I was driving today about 2 miles from home and the engine started to die (seemed like a fuel problem). I pulled the choke out some and it picked up a bit and after another 1/2 mile it quit running.
Thought maybe out of gas (still had a few gallons looking onto tank). Added 4 gallons.
Fuel pump glass bowl is full.
Tried starting but no luck. Pulled choke out really far and it started but would die instantly if choke was pushed in any amount.
Tried many times but no luck. Had to get towed home. :(
I cleaned this carb out last year, otherwise no idea when it has ever been rebuilt.
Maybe the fuel pump is not fully filling the carb bowl and with the choke out it will run on the last small amount of fuel ????
I know these updraft chokes are much different than the downdraft chokes.
Looking for ideas.

My experience has been if it runs better with the choke then there is trash somewhere in the carb. The choke causes less air to flow into the carb. If there is trash in the fuel mixture, it will cause less fuel. Reducing the air matches the reduced fuel due to the trash and causes the vehicle to run better. Most likely, with trash in the carb blocking the fuel line, you're running lean (too much air).

One quick thing to try is revving the engine up a slight bit and smothering the carb out with a rag and let go right before it dies a couple times, then smother it all the way out. Sometimes this will suck the trash through.

Trash in the carburetor is a fairly common event. Sometimes a tap on the fuel inlet fitting with a screwdriver handle can shake the needle loose if it is stuck in the seat. It is possible to drive 1-2 miles if the float bowl is full when the trip starts. Generally if the needle is wet with gasoline it will not stick. Once the needle dries out after the engine is shut down polymerized gasoline can glue it either closed or open.

Another possibility would be the idle adjustment screw. Often, the threads are worn, the spring is fatigued, and the screw can back out due to vibration.

The idle circuit is an inverse circuit (the screw meters AIR, not fuel). Turning the screw clockwise (in) makes the mixture richer. If the screw should backout then engaging the choke would artificially richen the mixture to allow the engine to run until the screw backed out further.

I would at least look at this setting (probably should be around 1/2 turn from closed) before doing anything more drastic. Check the easy things first

Jon.

Remove the brass bowl. Check for sediment in the bottom. Wipe with a cloth or paper towel.

Now... The real trick here is to clean out the brass nut that holds it on. Use a wire or paper clip. The metering rod fits inside the back side of the nut. When it fills up with sediment, the engine acts as you described.

Bill B

Found needle valve seat had worked loose which made for almost no gas in the fuel bowl. :)

Now runs great again.

Cool!