carb rebuild...stumped...problem solved????

[trm]

Re: carb rebuild...stumped...problem solved????

Hey Medic,<br />You've come a long way baby. Now you know the intricacies of rebuilding your carb and the importance of earmuffs in the summer A little frustration for us weekend mechanics now and then, but with all the help here and many saved bucks is the bank I like the challenge. I think you do too.<br /><br />Hope the impeller is OK... Hoot's advice above is good.<br /><br />Best of luck,<br /><br />Swabbie

 

[galaxy]

Re: carb rebuild...stumped...problem solved????

I second what hoot and swabbie said. Don't throw in the towel yet. Step back and take a breather. You'll get your second wind... then you can jump back in the fight. Summer will be over by the time I get my boat where it should be. But that's ok, I'll have it ready for next spring.

 

[medic]

Re: carb rebuild...stumped...problem solved????

Thanks for the boost of confidence. I really need it. Talk about frustrated. Just got off of a 16 hour shift and this has bugged me all day.<br /><br />Hoot, you say that gas DOES get to that area (of the idle mixture screws). Is it supposed to and how does it? How does air get to those screws? I was thinking that maybe something is up with the gasket under the venturi assembly and that maybe I rearranged the screws. I went and bought a manual and was looking through it and realized that I missed removing and cleaning one part. The "main well tube". They are plastic tubes that sit down inside the carb and the venturi tubes sit down into them. Could that be the problem? I cleaned them while they were in the carb. I did not know they came out. Looked like part of the carb to me. So I did not think twice about them being seperate from everything else. Also, in the the exploded view that came with the rebuild kit, I see a couple of items that I do not see on my carb. Is that typical? They look important but I don't see them. One has to do with "vent valve" and the other with "hot idle compensator".<br /><br />Anyways, I plan on taking it apart again and checking the gasket under the venturi. If this is how air gets to the idle mixture screws then I was thinking that maybe gas is crossing over there. A guy at work says I should try switching the idle mixture screws around.<br /><br />Sorry for rambling. Keep the help coming. I am on vacation next week and this is going to kill me.<br /><br />Medic

 

[magster65]

Re: carb rebuild...stumped...problem solved????

How much are they weeping? If they're just a tiny bit damp I'm not sure I'd be too worried but if they're dribbling... that's trouble. I've seen some Rochesters with small cork gaskets in the idle mixture slots above the threads. It keeps the screws from turning and seals them up better. They must be awfully loose if they're leaking badly.

 

[medic]

Re: carb rebuild...stumped...problem solved????

No they are not dripping. Just enough is seeping out to notice a wet ring around the screws (on the body of the carb) and not while running, but after it is shut off. More so around the right side screw. It seems to evaporate after some time. At least that is how I noticed things. Hoot says that gas does get to those areas and it only makes sense because they are called idle mix screws and not just idle air screws.<br /><br />Our mechanic at work says that he has some teflon paste that I could put on the threads. Sounds good to me if gas does indeed (supposed to) get to those idle mixture screws and the threads are the problem. I plan on getting some muffs today so I can run it longer, without damaging anything. I can wiggle the screws back and forth. I may try stretching the springs on them to make them tighter and switch the screws around.<br /><br />I am open to all ideas and solutions here and I appreciate all of the help. When I get this fixed I will be sure and let all know so that no one else has to go through this.<br /><br />Does anyone think that the problem may lie in the gasket just under the venturi assembly?<br /><br />Medic

 

[magster65]

Re: carb rebuild...stumped...problem solved????

I wouldn't put any kind of sealer on any carb... that's a big no-no. The idle mix screws regulate the amount of fuel that dispenses in the idle slots by the throttle plates. They don't gravity feed, they only pass fuel when vacuum is present. If those screws 'wiggle' they will weep a bit of fuel and probably go out of adjustment with the engine vibration. Put an appropriate sized o-ring in the hole the idle screws go in to seal it up. Your bottom gasket will have a bearing on this also because if it has a vacuum leak it'll cause irratic power valve operation.

 

[medic]

Re: carb rebuild...stumped...problem solved????

Ok. No paste. Instead an o-ring of somesort around the screw. So gas is supposed be there, just not weeping out of the screw holes? Which gasket are you referring to? The one between the throttle body and the manifold or the one between the throttle body and the bowl?

 

[galaxy]

Re: carb rebuild...stumped...problem solved????

Medic,<br />I still think your fuel leak is a gasket problem. There could be a misalignment or the wrong gasket. Double check your ventura gasket. You normally get a couple of those depending on the model you have.

 

[medic]

Re: carb rebuild...stumped...problem solved????

You know, that is the thing. I did not get any duplicate gaskets. I simply asked for a rebuild kit for my carb. Gave them the carb number off of the side and this is the kit they ordered for me. Triple checked. <br /> <br />I hope to go over there and check that venturi gasket again in a couple of hours. <br /><br />If I don't get something done today, I am going to have to wait a week. I am leaving for the beach in the morning.

 

[galaxy]

Re: carb rebuild...stumped...problem solved????

Did the new gaskets match the old? Anyway... Go to the beach my brother and worry about the carb later. Life is too short for all that we worry about

 

[magster65]

Re: carb rebuild...stumped...problem solved????

Both gaskets will have influence. <br />FYI (if you're interested)<br />Power valves 101.<br />The power valve, when at rest, is open. You turn the engine over and the tiny bit of vacuum pulls fuel in through the idle mix slots and the venturis via the power valve. This provides a rich mix to 'flash' the engine. Upon starting the vacuum created by the engine closes the power valve and the idle slot fuel maintains your idle. When you give it gas and load the engine the vacuum signal starts to drop off, when the vacuum signal reaches a determined amount it begins to open, allowing a richer mixture. The point at which the valve starts to open is often stamped on the valve itself... usually from 3.5 " for an engine with poor vacuum (big cam) to 13.5. Hope this helps.<br />You'll get it fixed today, I admire your determination. Happy boating

 

[medic]

Re: carb rebuild...stumped...problem solved????

Magster65, How do you propose that I will get it fixed today? I sure do hope so. The only thing I know to do right now is check the gasket under the venturi. I am confident that the throttle body/bowl gasket is correct, as well as, the throttle body/intake. But I don't know what else. Unless, it is true that, with gas reaching the point of the screws, like it is supposed to, that either I switched the idle mix screws or the springs are not tight enough or the threads are worn. Is all I need to do is put on some teflon tape, teflon paste or some type of o-ring, even though they are not shown in the parts diagram?<br /><br />I am still waiting for a phone call from a independant boat mechanic in the area.<br /><br />Medic

 

[medic]

Re: carb rebuild...stumped...problem solved????

The problem may be solved here. I went over to the boat. Tore the carb down and removed the venturi assembly and gasket. It was seated right except I noticed that the gasket was not lying flat. I trimmed the outer edge of it and put in back on. Perfect fit. Also recleaned the mating surfaces. I was also looking around and looked for those well tubes... like these and they are not there. No wonder I did not see them before. If you look closely at the pic you can see a what looks like a sleeve on the inside of the hole. That is all I have. What do these things do? Do they keep gas from getting to the two outer brass tubes on the venturi? Think that may be the problem?<br /><br />Anyhow, I put the carb back together. Took out the idle mixture screws and switched them around. Tried stretching the spring some and also put a rubber o-ring on each one. Put them back in (tighter fit) and fired it up. By the way...got some muffs. But since my brother-in-law is selling his house, they water was turned off today. Used the neighbors. Ran it for a min. Shut her down and waited. No seepage from around the screws. No leaks. <br /><br />Do you think that solved the problem? I hope so. Now if it will only run when under load. Read somewhere on here before that you won't notice anything until the engine is under load. Guess we will see. Let me know if you think there is more to this. I am off to the beach. I may try to check just before leaving to see if anyone has posted, but if not, I will talk to you guys in a week.<br /><br />Thank you and take care. Now I need to check that impeller.<br /><br />Medic

 

[magster65]

Re: carb rebuild...stumped...problem solved????

Atta' boy <br />The fun never ends!

 

[medic]

Re: carb rebuild...stumped...problem solved????

So you think that fixed the problem? What about those "well tubes"? Is it possible that my model of carb doesn't use them? Hoot...did yours?

 

[denniz]

Re: carb rebuild...stumped...problem solved????

Must have been a SIERRA carb kit, Ive noticed that gasket is cut wrong. Ive also noticed the accelerator pump hangs because the diameter of thepump is too large. Ive tried to use aftermarket crap and there is always something that doesnt fit right. Do your self a favor buy a MERC kit.