Marvel Schebler MA-3SPA CARB PROBLEMS

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citabrick
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Marvel Schebler MA-3SPA CARB PROBLEMS

Post by citabrick » Wed Aug 29, 2007 4:07 am

Recently the carb on my Citabria with an O-200A had a fuel leak. I sent the carb to a shop and had it repaired. While at the shop a one piece venturi and an atomizer style fuel nozzle were installed. Now my engine is not making full power and runs very rich. On a ground run, if I go full throttle the engine runs very rough and emits black smoke, if I throttle back to 3/4 throttle the RPM goes up and it runs smoother. I have sent the carb back to the shop and they even ran it on a test cell engine and can find no fault. Has anyone here had this problem? If so what was the cure?
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Post by .300 Weatherby Mag » Wed Aug 29, 2007 10:26 am

You may have an induction leak.
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Post by .300 Weatherby Mag » Wed Aug 29, 2007 10:33 am

Make sure you primer is locked and not leaking.
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citabrick
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Post by citabrick » Wed Aug 29, 2007 10:35 am

I should have also mentioned that the only way I can get it to run smooth and produce any reasonable power at full throttle is by leaning out the mixture. My field elevation is only about 800ASL. Sorry for omitting that fact.
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Post by hangarline » Wed Aug 29, 2007 12:14 pm

Are you running automotive fuel (mogas)? If so, try AVGAS. Big difference.
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Post by .300 Weatherby Mag » Wed Aug 29, 2007 4:53 pm

Get rid of that Marvel Schebler piece of shit and get yourself a Demon! :wink:

Seriously, are they sure they put the right needle and seat in? Float adjusted properly? Sometimes they run tops on the bench but the real world is different.
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Post by N2 » Wed Aug 29, 2007 6:27 pm

My Precision carb does exactly as you describe! It's been tested to hell and back a few times as well as the engine. Still to this day no satisfactory answers, even talked to a factory rep at Oshkosh about it and he suggested I send them the carb as he said they are the only ones who can properly flow test the unit.
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Post by Jungle Jim » Wed Aug 29, 2007 7:54 pm

Put the old venturi back in.


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Post by .300 Weatherby Mag » Thu Aug 30, 2007 6:14 am

Jungle Jim wrote:Put the old venturi back in.


Jim
One piece venturi is required by AD.
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Post by Jungle Jim » Thu Aug 30, 2007 7:15 am

Yes, I know about the AD but the two piece venturi works. Also the owner is the one responsible for maintenance these days. I'd rather fly a plane that performs as designed as opposed to a poor running one with a legal piece of paper on the book.

He should be able to state the situation in the log books and defer complying with the AD. ( quite a few champs are flying that have defered the spar inspection holes this way) I had a similar situation with the weight and balance when I bought my Stinson. The calculations done repeatedly over the years by qualified AME's were wrong. I revised them myself, sent the documents to TC and was told that the wrong calculations had to be the ones used because the AME's were deemed qualified persons. I challenged them on this and they did back down and accepted my calculations with my P.Eng. stamp in the end.


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Post by Strega » Thu Aug 30, 2007 11:43 am

This is a very common problem with the SP3A, Keep sending it back until you are satisfied with it. I struggled with your situation several times in the past.

Also good job challenging TC with your stamp!! Ive done the same on several occasions, with mixed response from TC.

Perhaps ask for the "Engineer" that is fixing your carb, to adjust the float level down a bit.
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Post by Hedley » Fri Aug 31, 2007 5:22 am

Shot in the dark: is the float sinking? There is quite the trail of AD's on this.
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Carb trouble

Post by Bulawrench » Fri Aug 31, 2007 8:39 am

I can't beleive a transport inspector accepting an idiot with a pinky ring having any say in an aircraft issue. The ring is there to remind you dumb f@%ks that you screwed up.
Give me a break. Go build a bridge.
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Post by Hedley » Fri Aug 31, 2007 12:13 pm

an idiot with a pinky ring
You mean, someone like a DAR? :wink:
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Re: Carb trouble

Post by Strega » Fri Aug 31, 2007 4:13 pm

Bulawrench wrote:I can't beleive a transport inspector accepting an idiot with a pinky ring having any say in an aircraft issue. The ring is there to remind you dumb f@%ks that you screwed up.
Give me a break. Go build a bridge.
My friend, it is people such as you, that keep this industry in the toilet.

Go and get an education.
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Post by hoptwoit » Wed Sep 05, 2007 10:26 am

This is not directed at anyone here but since we are on the topic.

Do not confuse an education for intelligence as they are not interchangeable.

By the way since the owner is responsible for maintenance did he submit an SDR to Transport regarding the carb problem?
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Post by twotter » Wed Sep 05, 2007 10:52 pm

I personally would send the carb back and say nice try, but this time do it right. I just had a carb on our 172 that is for employee use back to the shop 3 times before it worked right.

And bula, buddy, lighten up a bit.. Maybe I should bring you some medicine... :wink: :P OK.. We'll just go to the Beav and I'll let you buy!!
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Post by Strega » Wed Sep 05, 2007 11:13 pm

you are correct, intelligent people pursue higher education.
hoptwoit wrote:This is not directed at anyone here but since we are on the topic.

Do not confuse an education for intelligence as they are not interchangeable.

By the way since the owner is responsible for maintenance did he submit an SDR to Transport regarding the carb problem?
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Post by hoptwoit » Thu Sep 06, 2007 10:55 am

Strega wrote:
you are correct, intelligent people pursue higher education.
Kinda thought this might happen so in you're case we may have to apply the universal language of math. Let's see how could we write this formula?

(Strega's comment + attitude) / Higher education = Arrogance

You're comment smacks of it.

There are many intelligent people that have not sought higher education.

Perhaps a more appropriate statement would be. Intelligent people seek knowledge. :D

Please don't seek to elevate yourself by putting other people down. It's not becoming of the "Higher educated"
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Last edited by hoptwoit on Thu Sep 06, 2007 2:06 pm, edited 1 time in total.
People should not have to fear both the government and the criminal. It should be that the criminal fears both the people and the government.

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Carb trouble

Post by Bulawrench » Thu Sep 06, 2007 12:31 pm

Yeh, i guess i need to lighten up twotter . I think something struck a chord. My brotther has a pinky ring and as far as i remember his sh@t did stink when i was a kid. After all this is only for fun. Thanks Twotter.What day is cheep beer night anyway?
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Post by Strega » Thu Sep 06, 2007 10:59 pm

hoptwoit wrote:Strega wrote:
you are correct, intelligent people pursue higher education.
Kinda thought this might happen so in you're case we may have to apply the universal language of math. Let's see how could we write this formula?

(Strega's comment + attitude) / Higher education = Arrogance

You're comment smacks of it.

There are many intelligent people that have not sought higher education.

Perhaps a more appropriate statement would be. Intelligent people seek knowledge. :D

Please don't seek to elevate yourself by putting other people down. It's not becoming of the "Higher educated"
My point is not to put people down.
The grammar police here at avcanada can do that.
Im just saying that because of my education, training, and acomplishments, I am in a position to render an AME's calculations as incorrect.


S
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Post by twotter » Thu Sep 06, 2007 11:24 pm

It's cheap beer night every night when you work where I do!! We'll find a night that works.. Too bad you don't use Western, you could have had fun with us on the golf course tomorrow.. See Ya..
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Post by citabrick » Mon Sep 10, 2007 6:15 am

Here's a new development with my carb. I was doing some troubleshooting this weekend and pulled out my spark plugs and found something rather odd. The plugs of the front two cylinders were very light in colour and the plugs of the rear two cylinders were black. Seems like the fuel is not atomizing very well. Carb is going back to the shop today. Has any of you ever seen this? I'm getting really tired of this damn carb!
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Re: Marvel Schebler MA-3SPA CARB PROBLEMS

Post by JackNapier » Mon Mar 05, 2018 7:38 am

citabrick, did you resolve your problem with the carb and fouled rear plugs? Was the atomizer fuel nozzle free of clogs and was it matched to the type of float in the carb?
I saw a similar problem expressed on the shortwingpipers forum; although his nozzle was a home made peppermill and he detected the problems with cylinder temp probes.
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