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Big carb problem!!!


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I have su carbs on an l26 and it will start and idle, when I try to rev it up the rpms dont go up and I notice the throttle rail moves so the butterflys on the manifold side of the carbs obviously open.

 

The carb pistons on the side where the air cleaner bolts to do not open!! they will go up pretty easily when I push them up with my finger. So im guessing this is the reason why I run out of gas so fast? theres no air fuel mixture!! no air is coming in because the pistons dont go up!!

 

So my questions are,am I missing a vacuum line to the carbs? is it a damper problem? whats the problem? thanks

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the suction domes move independent of throttle plate angle depending on manifold vacuum present biased against damper oil weight, weight of the piston, spring weight on the piston and any sliding friction present.

the differential between the opening of the throttle plate and the opening of the suction dome exposes manifold vacuum to the CV (constant velocity) section of the cabe where the needle and jet is exposed to the airstream, and pulls gas from the jet and atmoizes it. The size of the needle at any given station determines cross sectional area of the jet exposed to the air and ultimately dictates total fuel flow possible under any condition.

 

Have you read the SU FAQ yet?

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haha this car is really pissin me off I hate carbs so much!! im just gonna put the damn l28et in already.

 

At the risk of coming off as rude;

 

If you cant master dialing in a carb or do not have a clue how they work, how are you going to setup EFI? You gonna just throw it in there and mis-match parts that werent designed to support each other without the knowledge base to re-engineer the fuel delivery and ignition system and hope its a bolt in?

 

Start with your carbs. Familiarize yourself with them and HOW they function.

Tonys reply is a really good summary of SU functionality. If you dont know what he is talking about try the SU FAQ as he suggested and even a simple google or hybridz search will yield the basic info you need to diagnose your carbs.

 

If you were closer to Salinas Id have been glad to meet you and help you out in person. I live right off of 101. SU carbs despite their abnormal style are really easy to work on once you grasp their functions.

search for "setting up SU's" or "rebuilding SU's" and you should find a ton of info. I seem to remember Ztherapy's website having some basic rebuild and tuneup tips that would help you out.

 

Ray

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At the risk of coming off as rude;

 

If you cant master dialing in a carb or do not have a clue how they work, how are you going to setup EFI? You gonna just throw it in there and mis-match parts that werent designed to support each other without the knowledge base to re-engineer the fuel delivery and ignition system and hope its a bolt in?

 

Start with your carbs. Familiarize yourself with them and HOW they function.

Tonys reply is a really good summary of SU functionality. If you dont know what he is talking about try the SU FAQ as he suggested and even a simple google or hybridz search will yield the basic info you need to diagnose your carbs.

 

If you were closer to Salinas Id have been glad to meet you and help you out in person. I live right off of 101. SU carbs despite their abnormal style are really easy to work on once you grasp their functions.

search for "setting up SU's" or "rebuilding SU's" and you should find a ton of info. I seem to remember Ztherapy's website having some basic rebuild and tuneup tips that would help you out.

 

Ray

Thanks ray and Ive been working on cars since I was about 9. all EFI! lol I have very little experience with carbs, its very possible for the easiest thing to be very hard depending on the person.

 

In my case its these dumb carbs but I understand what you guys are saying and im sure with some research, I will come to find out that carbs are actually very easy to work on like I always hear and easier than EFI, But as of right now EFI is all im used to and what I prefer.

Edited by Z31TURBODRAY
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As it is with people who swap from EFI to carbs becuase they are familiar with them, I make the same suggestion:

 

LEARN about the system, it only takes a couple of hours of reading.

 

Spend time reading and learning and less griping about it on the internet, and by that time you WILL understand the setup and will have fixed the problem.

 

Like guys who blame the EFI when they got the car, becuause it was the thing they understood the least, I get the funny sinking feeling you are blaming the carbs for the issues because you don't know what you are looking at.

 

You have given us nothing of substance to go on regarding troubleshooting---because you don't know what to give us. Learn the basics, then you will give us something we can go from.

 

If the car starts and runs, the carbs are working. That it 'doesn't accelerate' doesn't mean NECESSARILY the carbs are the fault. Is the car warmed up? How old is the gas? What oil is in the dampers? Blah Blah Blah...

 

You can't get nothing from nothing, and that is what is going on here now. Educate, do not regirgutitae. When you have a basic knowledge, maybe you can give us something more to go on---frankly you haven't given us anything from an EFI perspective that would solve anything either. It's a crap post. Make it better or give it up and delete it.

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hahaha ya I apaologize again tony its just so irritating to know that if the car was efi it woulda been running along time ago. The car is just stuck right now and this pisses me off, but ill take your advice...Ill try to calm down to allow my patience to go back up and then I will begin reading about useless carbs and then ill get back to you.

 

Oh and im pretty sure all the old gas has been burned up, Ive been puttin lots of gas in and it will all get burned up just from idling for like 10 mins. I also have not even drove it yet, since it doesnt rev up when I go to engage the clutch it just stalls obviously cuz its not gettin gas. I checked the dampers after unscrewing them and when I pull it out theres redish oil on them and theres resistance when I try to push the piston up with my finger, So im guessing theres enough oil in the dampers.

 

 

So its just basically liked I explained earlier... The butterfly side of the carb which is bolted to the manifold is opening when I give it gas because its connected to that throttle rail. So it has no choice but to open, now for the piston side of the carb...The pistons just stay shut at idle and when I gas it!!! therefore letting no air in to have air fuel mixture! therefore burning up all the gas quickly. soooo tell me what you would do in this situation?? I would love to learn about these carbs but really dont have alot of time right now to sit around and read about it, Ive always been a hands on learner!! tell me what do to do or show me what to do and there ya go! I learned somethin new lol

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I might be in your area this week. I wont have much time, but Id be willing to give you some pointers and take a quick look. It all depends on where in San Jose your at. I will be going up to Fremont if your near my path up there.

 

I dont think you would be having any better luck with an EFI setup for what its worth. Even a stock non-turbo basic L-jetronics system requires tweeking to get it to run correctly on an L(tweeking being restoration to the electrical components and tuning both of which you have not demonstrated with with the SUs. Hopefully you can extract my meaning). The systems are just to old and worn down to be thrown on any engine in most cases. The classic AFM and CTS woes would come back to haunt you much like the carb situation now. Despite how much of a "no brainer" EFI would seem to be, I very much doubt it would be the answer based upon the descriptions of your observations.

 

There are several others already in your area that would probably help you out as well.

 

Sit down and watch the Ztherapy video and read whatever you can find. Its worth the effort IMO.

 

I would venture to guess that your carbs are probably untouched as far as cleaning and synching on top of lack of tune. My guess is based upon your demonstration of lack of knowledge and makes me think you would not know to preform these tasks. Simply adjusting the mixture knob on the bottom wont get you very far if these other things have not been addressed first. Choosing an oil for the slide(piston) dampener is also part of the tuning. Sounds like you have ATF in there. Thats pretty common. Both the mixture knob adjustment and oil choice are things to be preformed after the carbs have a basic setup. They are not things you can just go in and start adjusting on an unknown set of SU carbs unless your trying to limp it home.

 

Without knowing a lot more information I dont think you will find even the most qualified SU guru out there that is going to be able to help you over the internet with your knowledge base. You have not even hinted at checking your plugs, synching the carbs, or making sure they are good carbs to start with. The butterflys and the slides move and that is all we are getting from this. Thats good, but not really helpful. If they didnt move then we would have some insight. You could be having non-carb related problems as well. Even compounded problems not related to the carbs themselves. A good example(and only an example) would be like if you fuel system isnt supplying the required fuel volume to the carbs and your ignition timing is off.

 

If you want your car to run you have a few options. The basic options are:

1. Make the time to understand the operation of the powertrain including carbs, ignition system, and basic engine components no matter how you get the knowledge(internet, books, in person). This leaves you in the position of being able to work on your car the correct way and most of the time come up with usable solutions to your cars issues. This requires that for the most part you make an attempt to educate yourself.

2. Pay a shop a lot of money to work on an antiquated(and mostly unknown to the new line of techs that have the spoon fed electronics and dont know a lot about the old cars and old systems) system to fix all your problems and cross your fingers they do it right. You might get lucky and find a shop that knows exactly how to work on your car though.

3. Try the EFI swap(probably more costly than Ztherapy carbs if installing into a non-EFI car).

4. Sell the car.

 

Im a hands on learner myself, but I find unless you have some of the coolest/trickest tools of the trade you just have to read sometimes. I did not fully understand SU carbs until I read a little. Once you understand their operation, working on them is fairly simple. Id take these any day over any 4 barrel I have ever seen for simplicity.

 

PM me if your interested in me stopping by Ill get you my contact info.

 

Ray

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Thank you very much ray, you offering to stop by has steered me away from blowin the damn car up! haha I will pm you my number and everything and if your goin to fremont my car is at a friends house only a couple exits away from fremont, so this should work out well especially since im free all week due to not bein able to find a damn job any where. pm sent!!

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Taken In Turn from a Logical Perspective:

hahaha ya I apaologize again tony its just so irritating to know that if the car was efi it woulda been running along time ago.

Why do you say that---what would you do to an EFI car that would have made it run? Why don't you tell us that, and then we can 'convert to the carburetted alternative'?

 

Oh and im pretty sure all the old gas has been burned up, Ive been puttin lots of gas in and it will all get burned up just from idling for like 10 mins.

"Pretty Sure" isn't sure---there is a drain plug on the tank, take a sample! If you have been putting gas into it that much and you are just idling....do you see gasoline flowing out the carburettors? Jet stuck in the down position, Float Adjustment, Wrong Fuel Pressure, normally using 'that much gas' would have you puffing black smoke out the tailpipe. If you run the car to operating temperature (don't EVEN TRY anything till it's at operating temperature)then try to do diagnostics---small throttle opening no rpm rise at all? Can it be feathered to gain rpm? AT OPERATING TEMPERATURE. Cold right now they will run like crap unless they are pig rich anyway.

 

I also have not even drove it yet, since it doesnt rev up when I go to engage the clutch it just stalls obviously cuz its not gettin gas. Now, which is it, you suck down gas by the gallons or you aren't 'getting gas'---I posit your conclusion of 'obviously' is dead wrong! Quit making assumptions and DIAGNOSE the issues step by step. What is the timing on the car, does the timing move when you move off-idle? What are the valves adjusted to? If you can get it hot, you can adjust the valves. On another post you mentioned doing sometehing with the ignition leads---IS THE FIRING ORDER CORRECT AND IN PHASE WITH #1 CYLINDER??? Two wires crossed in the right manner will let it idle, but it will run like shite anywhere else! And no, it won't necesarily pop out the intake!

 

I checked the dampers after unscrewing them and when I pull it out theres redish oil on them and theres resistance when I try to push the piston up with my finger, So im guessing theres enough oil in the dampers.

Again, you're obsessing on carb minutae, rather than carb performance and giving us precious little to go on as far as real diagnostic meat and potatoes (or fish heads and rice...)

 

 

So its just basically liked I explained earlier... The butterfly side of the carb which is bolted to the manifold is opening when I give it gas because its connected to that throttle rail. So it has no choice but to open, now for the piston side of the carb...The pistons just stay shut at idle and when I gas it!!!

Now for the SECOND TIME are you prepared to LISTEN THIS TIME? Entertain the thought THIS IS THE WAY THEY ARE SUPPOSED TO WORK! Please read this over 100 times so we can dispense with your next jump of illogic, shall we? What you say is 'gas it'---gas it how far? WOT? 1/4 throttle? HOW FAR? the piston will not open until sufficient engine load is present. So far you haven't given us enough specifics to know if this is what it should be doing, or if there is anything wrong. The piston being down will create higher vacuum at the jet and give MORE GAS in an 'accelerator pump action' BEFORE opening to enrichen the main circuit. If you would have taken the time to read the links and research on SU's you would know this and not be stuck in a loop of dispair drawing on faulty conclusions.

 

therefore letting no air in to have air fuel mixture!

Plain wrong assumption. Discard this thought. The car will idle and accelerate just fine from idle speed with the bridge almost touching the jet.

 

therefore burning up all the gas quickly.

But you said it obviously wasn't getting gas! Now it's flooding? Which is it, please realize that to troubleshoot this kind of stuff you have to be specific and keep YOUR conclusions or impressions out of it and just relate the FACTS of the operation. What is your throttle opening. What is the car doing when accelerated. Are you WOT and the car is just bwaaa bwaaaa bwaaaaaaaaaaaaa and sitting at idle without the pistons ever rising? What happens if you DON'T give it WOT and 'feather it'? Sounds like a stuck advance mechanisim at this point--but you haven't given anything much more than your original post. Perhaps the reason you're frustrated is you are continually looking at the SAME THINGS and therefore continue to draw the SAME CONCLUSION. The advice given earlier was to look elsewhere and be more specific. This has not happend as of yet.

 

soooo tell me what you would do in this situation?? I would love to learn about these carbs but really dont have alot of time right now to sit around and read about it, Ive always been a hands on learner!! tell me what do to do or show me what to do and there ya go!

If you are unwilling to take the step to learn about the carbs and expect a spoon-fed diagnosis, IMO you need to go to another site more befitting a beginner. You don't want to sit down and read, but you got all the time in the world to run in circles chasing your tail without an inkling or clue how the carbs work? Please explain that to me so it makes sense, because it just doesn't compute.Seems to me 45 minutes reading a book and learning how the damn things work would pay off FAR more than three hours of beating your head against a wall and swearing and getting frustrated because you're not making any headway! Hint: Your way isn't working, my suggestion is you try something else. The course is plotted, wether you take it or not is up to you. Good Luck.

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Ztherapy has a video on how to tune these carbs, plus other tuneup tips.

 

I guess I have to repeat myself...

 

If you don't want to put in the $20 investment for the video, at least learn how they work by searching online. I'll give you a site I know off the top of my head: http://zparts.com/zptech/articles/mal_land/ml_sucarb2/images4/SUcarb_111601d.htm

 

Listen to Tony.

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