3W150 carb-fuel problems-good one
05-09-2005, 09:35 PM
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3W150 carb-fuel problems-good one
Okay guys here goes. I picked up a used plane with a 3W150 the other day. Went to run it for the first time and started right up. The transition was horrible and the needles made absolutely no difference. I took the carb off and noticed that the previous owner was turning the butterfly backwards (beyond full throttle to the other extreme was closed-low throttle). I discovered this at home and corrected the problem. The next time out at the field the motor was a little more difficult to start. But once it did it didnt want to idle.
Now once it was running the transition was excellant.....absolutley perfect. The previous symptoms were that WOT was fine yet low to half throttle was terrible. When you increased to half ffrom low it was unresponsive, yet when you reduced to half from WOT if seemed fine. And I seem to recall that it would idle just fine.
But for what ever reason now I cannot get the motor to idle for any length of time before it dies. It just acts like it starves for fuel no matter where the low and high needles are. One thing I discovered when reinvestigating was that the screen was pushed in and wasent doing its job. I pulled it out and reset it but Im wondering if trash had passed by at some point and is causing my problems.
Supposedly this engine had been sent to Cactus Aviation last fall and was given a tune up and clean bill of health. I can tell this engine is super strong and is gonna be a great running motor if I can just figure out what is causing me this little problem.
Im also a little curious about the small brass jet just behind the high and low needles. It's got a hole at the bottom with 4 small holes around the lower edge. The hole in the bottom has a small spring loaded ball that acts as some sort of regulator/vavle from what I can tell. Im wondering if this could be causing my any problems if its getting stuck.
Also, all of the rubber in the carb looks great, the diaphram *** is properly hooked into the pump fork, and everything else from what I can tell is normal.
Maybe I just have a piece of trash somewhere causing me problems on the low end since it just acts like it starves at low throttle.
PLEASE HELP ME!
Now once it was running the transition was excellant.....absolutley perfect. The previous symptoms were that WOT was fine yet low to half throttle was terrible. When you increased to half ffrom low it was unresponsive, yet when you reduced to half from WOT if seemed fine. And I seem to recall that it would idle just fine.
But for what ever reason now I cannot get the motor to idle for any length of time before it dies. It just acts like it starves for fuel no matter where the low and high needles are. One thing I discovered when reinvestigating was that the screen was pushed in and wasent doing its job. I pulled it out and reset it but Im wondering if trash had passed by at some point and is causing my problems.
Supposedly this engine had been sent to Cactus Aviation last fall and was given a tune up and clean bill of health. I can tell this engine is super strong and is gonna be a great running motor if I can just figure out what is causing me this little problem.
Im also a little curious about the small brass jet just behind the high and low needles. It's got a hole at the bottom with 4 small holes around the lower edge. The hole in the bottom has a small spring loaded ball that acts as some sort of regulator/vavle from what I can tell. Im wondering if this could be causing my any problems if its getting stuck.
Also, all of the rubber in the carb looks great, the diaphram *** is properly hooked into the pump fork, and everything else from what I can tell is normal.
Maybe I just have a piece of trash somewhere causing me problems on the low end since it just acts like it starves at low throttle.
PLEASE HELP ME!
05-10-2005, 06:05 AM
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RE: 3W150 carb-fuel problems-good one
If it was mine, I would tare the carb down and clean it port to port. Blow out all ports, bleed holes, check and clean the fuel regulator.
Check the point of your low end needle and the seat. Sometimes someone will screw the needle in too far and mess up the seat and point. This will cause the same symptoms you are experiencing.
Check the point of your low end needle and the seat. Sometimes someone will screw the needle in too far and mess up the seat and point. This will cause the same symptoms you are experiencing.
05-21-2005, 06:43 AM
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RE: 3W150 carb-fuel problems-good one
Which model 150 is it? Does it have the phenolic, or black carb mounting block?
Is the block flat, and are the gaskets sealing properly?
There are a ton of threads on this subject here, and on the Scale Aerobatics board.
That's a yahoo board, but lots of the gas fliers use it, and it's a great source of information.
Do you have a Walbro or Tilottson carb?
Is the block flat, and are the gaskets sealing properly?
There are a ton of threads on this subject here, and on the Scale Aerobatics board.
That's a yahoo board, but lots of the gas fliers use it, and it's a great source of information.
Do you have a Walbro or Tilottson carb?
05-22-2005, 11:37 AM
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RE: 3W150 carb-fuel problems-good one
Yeah I'm the guy that posted the question on the Scale Aerobatics board. Absolutely incredible the amount of quality assistance that I recieved from those guys. But to answer your question, yes it's the phenolic block...yes it was warped....Walbro WGA-7 carb that has now been replaced. And the good news is that I think I've got the problem corrected. Im going to share my findings when I get home and back to my email.
