fuel carb mystery on my 135

[Forester Massey]

Rebuilt the massey last winter and summer and she has been running good until it acted like it was not getting fuel. Here is what I can't figure out and why it won't start most of the time. Its as if I have a vapor lock situation without it being hot.

When I turn on the gas at the value (starting with an empty bowel) it only drips into the sediment bowel. If I take off the bowel gas will run out of tank fine. I realize for gas to flow it must displace the air in the line and that is not happening.

Hopefully someone knows what may be causing the problem.

 

[Coyote machine]

Try removing the gas cap. See what happens then. Report back results.

 

[The kid]

Rebuilt the massey last winter and summer and she has been running good until it acted like it was not getting fuel. Here is what I can't figure out and why it won't start most of the time. Its as if I have a vapor lock situation without it being hot. When I turn on the gas at the value (starting with an empty bowel) it only drips into the sediment bowel. If I take off the bowel gas will run out of tank fine. I realize for gas to flow it must displace the air in the line and that is not happening. Hopefully someone knows what may be causing the problem.

Have you recently replaced the fuel cap. The new caps seem to be really tight as far as pressure. I placed a piece of plastic up into the vent hole ( bottom center under cap) to assure if was open and no more problems. If air is not venting into the tank how can it gravity drain to the bowl. It's like a fuel can pouring and without air going in none or little will come our. -kid

 

[namyessam]

If the carborator fuel bowl is full and the float is at its top position, the needle valve is closed so there is nowhere for the air to be pushed out out of the sediment bowl through the fuel line to the carborator.

 

[The kid]

If the carborator fuel bowl is full and the float is at its top position, the needle valve is closed so there is nowhere for the air to be pushed out out of the sediment bowl through the fuel line to the carborator.

The carb doesn't just push air out of the fuel lines what you've described on the float is exactly the way it"s suppose to work. Keep the bowl full till the carb calls for gas by opening jets. Air trapped in the bowl will be pulled into the carb causing a sudden faulter but only momentary till more fuel is dumped into the sump as the float allows it. Air will purge itseft in the fuel line. If there is a restriction as in plugged inlet inside the tank. Faulty needle valve seat can and will cause a failure. Air gets in when no flow from the tank and the carb is starved this creating a void of no fuel in the bowl or line. Air leakage thru gaskets in the carb at the bolting point could lower the vacuum that creates the pull for more gas and causing gas starvation.

 

[Forester Massey]

The carb doesn't just push air out of the fuel lines what you've described on the float is exactly the way it"s suppose to work. Keep the bowl full till the carb calls for gas by opening jets. Air trapped in the bowl will be pulled into the carb causing a sudden faulter but only momentary till more fuel is dumped into the sump as the float allows it. Air will purge itseft in the fuel line. If there is a restriction as in plugged inlet inside the tank. Faulty needle valve seat can and will cause a failure. Air gets in when no flow from the tank and the carb is starved this creating a void of no fuel in the bowl or line. Air leakage thru gaskets in the carb at the bolting point could lower the vacuum that creates the pull for more gas and causing gas starvation.

I think it has something to do with one of the jets, the main jet possibly. I will try removing main jet and blowing air into it and retry. I will post my results.

 

[The kid]

I think it has something to do with one of the jets, the main jet possibly. I will try removing main jet and blowing air into it and retry. I will post my results.

Because of ethanol, a lot of carbs are getting damaged jet seats. The metal become porous and no longer will seal. Especially the float needle valve. I can't remember if mine (Z145) had a neoprene seat for the needle.it's been. A while. You can strip some stranded #12 wire and use a strand to poke down into jet openings to make sure something is not clogging it. If using air use low pressure. If your using a cleaner to clean the carb. Don't use spray carb cleaner. It's main use is to clean off junk on the outside. Use a petroleum based cleaner and a low pressure pressure blow gun.

 

[Jerry/MT]

Rebuilt the massey last winter and summer and she has been running good until it acted like it was not getting fuel. Here is what I can't figure out and why it won't start most of the time. Its as if I have a vapor lock situation without it being hot.

When I turn on the gas at the value (starting with an empty bowel) it only drips into the sediment bowel. If I take off the bowel gas will run out of tank fine. I realize for gas to flow it must displace the air in the line and that is not happening.

Hopefully someone knows what may be causing the problem.

Is there a bowl drain on trhe carb's fuel bowl? If there is open the tank valve fully and then remove the plug from the bowl drain, holding a suitable container under the carb to catch the fuel. The gas should gush out CONTINUOUSLY, like a cow peein' on a flat rock. If it dribbles or is intermitent you'll have to check the tank vent and from the fuek tank pick up to the carb for blockages.

There is filter screen in the sediment bowl but you said you had full flow there so I'd look down stream. Is there a screen at the fuel elbow where it enters the carburtor? The Marvel-Schebler carbs had a screen there. Is the fuel line restricted, bent, or kinked? Is the tank vent blocked? If you can't find anything betweeen the tank and the inlet to the carb, then you'll have to pull the carb and look for a blckage in the area of the float valve and check the float setting while you are at it.