How much torque for carb fuel fitting.

[redtim]

I just pulled the carb and cleaned it out, despite being brand new, there was a ton of crap in there.

The reason i have a nice brand new carb...

PO had tried to cure a fuel leak by cranking down on the fitting as hard as he could, and cracked the old one. He had installed this one (without hose clamps )

My question, how much torque should I be applying? I was only able to get about 2 full turns in by hand, and was getting a lot of fuel leaking out.

Ordered some of this stuff
http://www.permatex.com/products-2/p...sealant-detail

and hoping that helps but i'm a little nervous to really tighten the fitting down too much due to the POs experience. Any thoughts?

[BunnyPlanet169]

Two thoughts:

There is some variation in fitting geometry. Assuming the female threads are clean, take the carb to the hardware store, and see if you can't find a fitting that threads in a little deeper.

Given the cast aluminum body, I wouldn't go more than about an extra 1/2 or 3/4 turn past hand tight, based on wrapping the male end about 2 or 3 times around with Teflon tape. You kinda have to get a feel for it.... With a goopy goop compound, I'd do less.

[JOHN COOKSON]

The old fitting may have been cross threaded a bit and the PO tried to fix the problem by excess tightening. If you can figure out the tap to use it might be a good idea to clean up the threads. Or maybe you can use the new fitting as a tap. Aluminum is soft stuff so go easy. Alternate 1/3 turn in and 1/4 turn out.

TRUE GRIT

[JOHN COOKSON]

Originally Posted by redtim

I just pulled the carb and cleaned it out, despite being brand new, there was a ton of crap in there.

Did you ever figure out how the "ton of crap" got into a new carb carb?
I would not install a new carb until you can be assured you are delivering "crap free" fuel to it.
What do you have for filters? Does the tank have a lot of KRAP in it - possibly loosened by ethanol in the poor excuse we have for gasoline these days?

TRUE GRIT

[The Garbone]

Usually just snug up the fittings, too tight can be bad.

I usually put a single wrap of the yellow teflon tape on the threads. It really is not needed for a seal but does help smooth fitment and act as a dielectic against corrosion on the dissimilar metals.



Edit..
Oh , I basically just repeated Jeffs post. My bad.

[redtim]

Originally Posted by JOHN COOKSON

Did you ever figure out how the "ton of crap" got into a new carb carb?
I would not install a new carb until you can be assured you are delivering "crap free" fuel to it.
What do you have for filters? Does the tank have a lot of KRAP in it - possibly loosened by ethanol in the poor excuse we have for gasoline these days?

TRUE GRIT

I cleaned out the whole fuel system, replaced the racor filter, cleaned out the sediment bowl, pretty sure i'm getting clean gas now

[67c&ccorv]

Originally Posted by The Garbone

Usually just snug up the fittings, too tight can be bad.

I usually put a single wrap of the yellow teflon tape on the threads. It really is not needed for a seal but does help smooth fitment and act as a dielectic against corrosion on the dissimilar metals.



Edit..
Oh , I basically just repeated Jeffs post. My bad.

Generally speaking teflon tape of any type should not be used with fuel fittings and components;

How to choose thread sealant for fuel applications

"To choose the appropriate thread sealant, look for it's chemical resistance to fuel (diesel or gasoline) or oil running through the line. Backyard mechanics will tell you they've used regular old gas resistant teflon tape (yellow stuff) with success. This is not recommended because it risks breaking free. Liquid or paste type thread sealants are kinder to sensitive components down stream. Mechanics repairing injectors, fuel pumps and carburetors can tell you first hand it is not uncommon to trace fault in the fuel component to clogging from a piece of teflon tape that washed off the ends of the threads, clogging in the first tiny micron orifice it encounters, if not the fuel pump then an injector or carburetor gallery. Either way it's a costly repair. Liquid or paste type sealant won't clog. For gasoline, regular old gasoline resistant Aviation Form-a-gasket Number 3 is the best option. Another product also offered by Permatex is the High Temperature Thread Sealant. Tech data on this sealant says it has medium solvent resistance and is recommended for fuel sender type applications. With the advent of ethanol present in modern gasoline, I favor Form-a-gasket No. 3 which specifically states solvent resistance to gasoline, especially on modern engines that use injectors rather than carburetors such as the E-TEC and HPDI (high pressure direct injection) and any diesel engine.

Whenever making these connections from a threaded port to hose barb connection, ABYC guidelines call for two hose clamps at each connection point of fuel line over hose barb. Be sure the clamps are a marine grade stainless steel type with even sealing tension. Doubling up the clamps does requires a hose barb long enough to fit both clamps. If you are installing fuel tanks or repowering a vessel, be sure to consult a professional or at minimum have your finished work inspected to be sure there are no siphoning and fuel leak hazards. It is a good idea to have the system pressure tested by a professional anytime you make alterations to a fuel line assembly."

[Al Schober]

Red,
If you're only getting two turn by hand, there may not be enough thread in the hole. Time for a tap drill (5/16") and a 1/8" NPT tap - a good hardware store should be able to help you out (probably not HD). Run that thread in a little deeper.
I generally figure I can go 1 turn with a wrench from finger tight to get the fitting aligned the way I want. If finger tight is almost there, I may push it a bit and go slightly more than one turn with the wrench.
Pipe threads need a sealant. The male and female threads make contact on the flanks of the threads, leaving a leak paths at the root and crest of the male thread.
My sealants of choice are a) the brown aviation Permatex for fuel/oil connections, and b) the blue silicone from Permatex for water systems.

[BunnyPlanet169]

With the advent of ethanol present in modern gasoline, I favor Form-a-gasket No. 3 which specifically states solvent resistance to gasoline

Gasoline, yes. Ethanol containing gasoline, specifically no.

http://www.permatex.com/component/do...ket=automotive

From the data sheet:

Chemical / Solvent Resistance
The product retains effective properties in contact with water, ethylene glycol, non-ethanol containing gasoline, motor oil, transmission fluid, and sea water.

[redtim]

Thanks Jeff, found some of the brown permatex on the boat, that seemed to do the trick.

Went about 3/4 of a turn past hand tight, to get to the position I wanted. No more fuel leak. Cleaning out the carb seems to have cured my lack of idle performance. I'm still stuck with low RPMs.

Next up, check the timing. The low rpms plus blowby when I get past 1500 are giving me hope that my timing might be too retarded. At least this thread is giving me hope anyway

http://www.moyermarine.com/forums/showthread.php?t=6408

All this learning is going to leave me stuck with our little engine for the rest of my life I fear...

[Beyent]

Hi Afourians. I need help again but first I want to say that I received excellent advice and clear answers to the questions I had about my Atomic 4.

I had a gas leak on my 1979 A4 at the carb fitting. I used Teflon tape on the threaded part of the fitting and tightened the fitting as much as I could with a half-inch wrench. Now it leaks worse than ever.How do I find out if getting a larger fitting thread is the solution? Is it possible I cracked the carburetor and need a new carburetor. I am no mechanic and I'm wondering if I should take off the carb and bring it to an service station for repairs.

Thanks in advance for any advice you may have for me.

[Marian Claire]

Beyent.
My experience is the same as others posted earlier. Just a half turn or so past snug should do it. No need to hog down on the fitting.
I do not think getting a "larger fitting thread" will work unless you retread the female part. They just wont match up.
It could be cracked, cross threaded or just have buggered up threads. Only way is to get a good look at all the parts so removal my be your best option.
Are you sure that the leak if from the fitting to carb connection? Or could it be the fitting to fuel line connection.
I am assuming that the fitting is barbed for flexible fuel line. If so how was the old line removed? If you had to cut it off the barbs could be damaged and causing the leak. No amount of tightening the hose clamp will solve the problem. BTDT.
If you have the old copper line it might be time to switch. I found the old copper line a real PITA.
Dan S/V Marian Claire

[JOHN COOKSON]

Originally Posted by Marian Claire

Beyent.
No need to hog down on the fitting.
I am assuming that the fitting is barbed for flexible fuel line. If so how was the old line removed? If you had to cut it off the barbs could be damaged and causing the leak. No amount of tightening the hose clamp will solve the problem. . If you have the old copper line it might be time to switch. I found the old copper line a real PITA.
Dan S/V Marian Claire

Over tightening hose clamps will destroy a hose - pronto.

I assumed that he had flexible line. Now I'm not so sure. Maybe he has a copper tube with compression type fittings at the ends between the fuel pump & carb. That's how my boat came from the manfacturer.

TRUE GRIT

[Beyent]

I talked to a service station mechanic friend of mine, who said to take off the carb and bring it in. He took one look and said the carb is cracked at the fitting and will need to be welded unless I can find a replacement part.

How do I know what kind of carb I have. I assume its a Zenith 68 series because my C&C is a 1979 and I have the original "Blue Book" Manual for the Atomic 4 Medalist Universal which refers to the Zenith 68 series.

However, I don't know how I can find out what carb I really have or how to find out if I can get a replacement part. Can anyone advise me.

Also, there when my electronic Facet fuel pump failed, I installed a new one and left the old one in place because it had what looked like a sensor which had a wire running to the fuel pump. A friend who helped me said to leave in place the wire which connects the senor to the old fuel pump. Is that a good idea. It seems to me that there is no point in having the senor (if that is in fact what it is) connected to the old fuel pump. Any suggestions as to what to do. How do I test the senor to find out if the old fuel pump failed or if the senor is defective. I tried to remove the sensor but it wouldn't budge and I didn't want to break it.

Thanks for any help

[Marian Claire]

Is the carb aluminum or cast iron?
3. To order carburetor parts, you will need to know if your carburetor is made of aluminum or cast iron. Aluminum carburetors were used on late model engines. All carburetors were manufactured by Zenith or Bendix, so the manufacturer does not help in determining your carburetor vintage.
From. http://www.moyermarine.com/faq/11.14.html
Sensor? You may be talking about the OPSS, oil pressure safety switch, found here,
http://www.moyermarine.com/cgi-bin/s...rebuilder.html

Dan S/V Marian Claire

[JOHN COOKSON]

The OPSS is a pressure sensitive switch that closes when the oil pressure is up when the engine is running. The OPSS prevents the electric fuel pump from operating unless the engine is running. Said another way for power to get to the electric fuel pump it needs to go through the OPSS first. An OPSS is a Coast Guard requirement. Look on page 20 of your "blue book" and you will see how it is wired into the circuit.
Testing the OPSS is easy. You can bypass it by running a hot wire to the wire to the fuel pump or short across it with a jumper wire or a screwdriver across both terminals.
Put up a post or send me a PM if you have questions.

TRUE GRIT

[Beyent]

Thanks to all who responded to my questions with such helpful and clear answers.

The carb could not be welded. However, a carb specialist mechanic used epoxy which he says is stronger than a weld in any event. So, I'll be installing the carb tomorrow. The fuel pump tested okay so perhaps it is the OPSS that is at fault. I'll test it tomorrow as suggested by True Grit. I'll keep you posted as to the results. I really need everything to work tomorrow since my boat is scheduled for lift out Sunday a.m.

[brewgyver]

Beyent,
If you have another issue, please try to post a picture. I read through the entire thread, and still have no idea which type of connection you have at the carb: npt x hose barb or compression.