Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

carburetor experts?


  • Please log in to reply
45 replies to this topic

#1 soobiefreak85

soobiefreak85

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Sherwood, Arkansas

Posted 18 September 2012 - 08:14 PM

So, I just finished rebuilding my 87' ea81 motor. I flushed and rebuilt the carburetor as well. All went well, however, I drove it several days with a high idle. It ran smooth, but at about 1500 rpms or so, never stalled and it started quick every time hot or cold.

After some inspection, I found the idle screw was backed off all the way and the accelerator cable was the same, so that wasnt the high idle issue. I found a hard to reach screw at the bottom (I think it is fuel/air mixture) and messed with it...biggest mistake ever!! I managed to lower the idle, however, it runs poorly, stalls at times, and has troubles starting at times also. I adjusted the idle screw as well trying to find the happy medium, being unsuccessful. Basically, it is unreliable now...sometimes it runs like a top or I have several issues. I cant manage to get it back to where it was. I would deal with the high idle for reliability.

Thoughts on fixing this? Do I adjust it with the choke unplugged, or is there a factory setting I can turn it too? A trick of any kind? Help!! By the way, I dont have the money for a Weber right now.

Wes

#2 Mykeys Toy

Mykeys Toy

    Subaru Master

  • Gold Subscribers
  • 1,930 posts
  • South Prairie, Wa

Posted 18 September 2012 - 08:49 PM

Well start with your fuel mix ( my car likes it not quite two turns ). Then readjust your idle. I still haven't plugged in my choke but just finished my swap right before the show. That should get you running right. Your symptoms tell me that is where your problem lies unless you messed with your timing or are in need of of a tune up.

#3 spazomatic

spazomatic

    USMB is life!

  • Members
  • 327 posts
  • castle rock

Posted 19 September 2012 - 06:12 PM

If there's nothing mechanical keeping the idle that high (idle speed screw, or linkage) than I'd suspect a vacuum leak somewhere.

stock carb? are all your emissions doodads still hooked up?

#4 Mykeys Toy

Mykeys Toy

    Subaru Master

  • Gold Subscribers
  • 1,930 posts
  • South Prairie, Wa

Posted 19 September 2012 - 06:19 PM

How tight is the linkage nut with lock plate thing? Mine needed to be backed off one sixth of a turn and all was good.. It will cause the car to idle high and run like crap because it is opening the secondary with any throttle movement.. I wouldn't know anything about that:rolleyes:

#5 mikaleda

mikaleda

    1000+ member!

  • Gold Subscribers
  • 1,329 posts
  • priest lake, Idaho

Posted 19 September 2012 - 07:33 PM

I'm not an expert but it sounds to me like the screw you were messing with is the idle air valve. To adjust that you warm engine up till choke is open and tighten until the engine stalls and then back off a quarter turn. At least that is how I do it.

#6 soobiefreak85

soobiefreak85

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Sherwood, Arkansas

Posted 19 September 2012 - 08:19 PM

Well start with your fuel mix ( my car likes it not quite two turns ). Then readjust your idle. I still haven't plugged in my choke but just finished my swap right before the show. That should get you running right. Your symptoms tell me that is where your problem lies unless you messed with your timing or are in need of of a tune up.


Not quite two turns? Do you mean turn the all the clockwise tight, then back off almost 2 complete turns. Or thread all the way off, then turn clockwise 2 complete times.

I didnt mess with the ignition timing at all. New plugs, wires, cap and rotor. It ran beautiful, but a little high idle until I messed with that screw.

After looking in the haynes manual it is the "secondary fast-idle screw", it says to adjust it to angle, not sure how to measure the angle.

#7 soobiefreak85

soobiefreak85

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Sherwood, Arkansas

Posted 19 September 2012 - 08:22 PM

If there's nothing mechanical keeping the idle that high (idle speed screw, or linkage) than I'd suspect a vacuum leak somewhere.

stock carb? are all your emissions doodads still hooked up?


It is the stock carb, I eliminated all the emissions crap prior to messing with the screw. It ran great without all that ************, and cleaned up the engine bay :)

Everything is capped off with new caps, and I put new vacuum lines on there. The few that are left.

#8 Mykeys Toy

Mykeys Toy

    Subaru Master

  • Gold Subscribers
  • 1,930 posts
  • South Prairie, Wa

Posted 19 September 2012 - 09:25 PM

My mistake I assumed with your previous post that there was a weber swap in there. So to amend my previous post I agree that there is a vac leak somewhere. I have picked up the wrong caps in the past and had to go back for a smaller size.. 1/8th I think

#9 soobiefreak85

soobiefreak85

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Sherwood, Arkansas

Posted 19 September 2012 - 09:45 PM

They seem darn tight on there. I dont think there are to many vac leaks, they may resolve the high idle issue, not the adjustment screw issue

#10 ferox

ferox

    King of the Echo People

  • Members
  • 796 posts
  • Portland, Oregon

Posted 20 September 2012 - 01:34 AM

I found a hard to reach screw at the bottom (I think it is fuel/air mixture) and messed with it...biggest mistake ever!! I managed to lower the idle, however, it runs poorly, stalls at times, and has troubles starting at times also.


Sounds like you messed with the fast idle screw and you are correct, fooling with it is at least one of the biggest mistakes on a Hitachi (assuming it's a Hitachi). To adjust it back to spec according to the FSM you have to remove the carb and adjust the screw while measuring the clearance from the throttle valve to throttle bore. I scanned a page out of my FSM but I can't attach PDFs, so I will try to scan it in a different format this weekend. It's a pita. The clearance is like 1.38 mm. I have done it once and filed a piece of wire and measured it with a micrometer to make a wire gauge for the adjustment. Even then the adjustment wasn't terribly accurate but close enough.

I agree with the other responses that it sounds like you have a vacuum leak. It might not be at the carb itself. If you have your charcoal canister hooked up, the valve on top of the canister could have easily failed or other things that your vac lines are hooked up to could be leaking.

What's you timing set at?

#11 spazomatic

spazomatic

    USMB is life!

  • Members
  • 327 posts
  • castle rock

Posted 20 September 2012 - 08:36 AM

Its my understanding that the hitachi will not work properly without the emissions junk hooked up and working right. I may be wrong there.

Do yourself a favor...consider a weber swap. Mine runs better now than it ever did when it was stock.

#12 Gloyale

Gloyale

    It's a sickness

  • Members
  • 8,557 posts
  • Corvallis, OR PNW

Posted 20 September 2012 - 09:59 AM

Its my understanding that the hitachi will not work properly without the emissions junk hooked up and working right. I may be wrong there.

Do yourself a favor...consider a weber swap. Mine runs better now than it ever did when it was stock.


They work fine without "emmissions" stuff.

What they don't like, is when you remove the Air Control valve that feeds air to the emulsion tubes. Those are the 2 large lines that looped into the UFO looking deal.

Those lines have metering orifices in them. If you cap off those lines, you get rich mixtures, and poor or no idle. If you leave them wide open, you get lean mix, high idle....but no power.

What you need to do is "T" those lines toghether, and hook them into the airbox. Each line needs to be restricted down to about a .5mm orifice inside.

Taking out a perfectly good carb, and replacing it with off the shelf generic "weber" won't make the engine run any better. It's still a carb, and requires tuning........and most importantly, an understanding of HOW a carb works.

#13 ivans imports

ivans imports

    1000+ Super USER!

  • Members
  • 2,902 posts
  • lumby bc canada

Posted 20 September 2012 - 11:04 AM

TBI TBI TBI works very good

#14 Loyale 2.7 Turbo

Loyale 2.7 Turbo

    The Mighty "BumbleBeast"

  • Gold Subscribers
  • 5,385 posts
  • Roatán, Honduras.

Posted 20 September 2012 - 04:43 PM

Please excuse my ignorance, but... What is the Meanin' of TBI? :confused:

Also, I Agree that a Weber will Simplify things and increase the Engine's performance, but if your Subie has to Pass Emission Test, forget it.

Kind Regards.


#15 djellum

djellum

    Eat, Live, Breath Subaru

  • Members
  • 556 posts
  • Vancouver WA

Posted 20 September 2012 - 04:52 PM

I first had it set up like Gloyale said, with the front and back ports connected and a hose to the airbox, but it wasnt running right and would die at odd times. it turns out that the back port was dribbling liquid gas into the hose and when it built up or I turned right it would suck it up into the other port and kill the car.

I ended up just plugging them. it works well this way, though I dont know if its another carb problem that caused the raw fuel in the line or if its normal. I would say it does run a little rich, but rich is better than lean, and I have no power, idle, or driving issues. I still get 28 mpg highway and it runs smooth at all rpms so I dont think it is too far off.

I liked the vac gauge method. hook up a vacuum gauge to manifold vacuum (i used the port below the carb) turn your mixture screw in all the way, then turn it out 2 full turns. screw in the idle screw till it touches, then just a little farther so you know it will idle a little high, then start it. turn down the idle to 750, tweeking the mixture a bit to smooth it out if it starts to stumble. you should try to achieve a smooth idle at 750. once you do go to the vacuum gauge. adjust the mixture and idle screws to attain the highest and smoothest vacuum reading at 750 rpms with the leanest mixture. it should end up where your 20+ on the gauge, with very little needle wiggle, at 750 rpms or lower, and turning in the mixture screw in will cause the needle to move around. You will be very close at this point, I then went behind the car and tweeked the mixture a tiny bit to eliminate any bad smells from the exhaust.

#16 spazomatic

spazomatic

    USMB is life!

  • Members
  • 327 posts
  • castle rock

Posted 21 September 2012 - 11:16 AM

Taking out a perfectly good carb, and replacing it with off the shelf generic "weber" won't make the engine run any better. It's still a carb, and requires tuning........and most importantly, an understanding of HOW a carb works.


While im not very familiar with hitachis, i do understand carbs and how they work. My weber took a fair amount of fiddling to run properly. No off the shelf carb is a bolt on and go affair. But tuned right, it runs circles around the hitachi. Just sayin

#17 soobiefreak85

soobiefreak85

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Sherwood, Arkansas

Posted 21 September 2012 - 08:48 PM

I have heard raves and raves about weber...after fiddling with the hitachi for a week now, I can see why. I have been working on cars for years, but I have limited experience with carbs. That is my problem. I had it running great, with all the emissions crap off including the UFO thingys, but just at a higher idle. Then I messed with the bottom screw and have has problems since. After all of you guys help, I adjusted it all the way down and then backed off 2 turns, it has troubles starting at cold (sometimes it starts with no problems), but eventually starts. Runs great and all of the sudden out of the blue, it dies. If I adjust the bottom screw a little while it is running, it dies and it wont start again till I let it cool, then I can barely get it started...it warms up and dies. I have to get the idle screw a little high to keep it running for a short time.

I am so frustrated, I just want to get it running again. I dont even care about the high idle haha. I had it running (at a high idle) and starting on a dime everytime, but ever since my ********************* messed with that bottom screw it either wont start, runs great and randomly stalls after a few mins or runs like ************...I never know. I wish I had the money for a weber, I have heard so many good things about them. Simpler and easier to tune up. I think I oughta just take to a shop, I just cant figure it out on my own. I am getting tired of adjusting back and forth with same results, I am staying in that 1.75 - 2.5 range grrrr:banghead:

#18 Gloyale

Gloyale

    It's a sickness

  • Members
  • 8,557 posts
  • Corvallis, OR PNW

Posted 21 September 2012 - 09:10 PM

Have you opened it up and blown out the Emulsion tubes?

If not, you should.

In my experience, all the hitachi issues trace back to clogged emulsion tubes and jets.

#19 soobiefreak85

soobiefreak85

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Sherwood, Arkansas

Posted 21 September 2012 - 09:24 PM

If those are the UFOs looking things, I took those off a week or so ago. It ran great until I messed with the bottom screw.

I could try to put them back on (like you said earlier) and "T" them together, if you think it has value

#20 djellum

djellum

    Eat, Live, Breath Subaru

  • Members
  • 556 posts
  • Vancouver WA

Posted 21 September 2012 - 11:28 PM

I would hook up that vacuum gauge. they are great for tuning, but they also show signs of other problems and can help you find and diagnose vacuum leaks, valve train issues, etc. even if you had a weber on there now it may be doing the same things. they arent magic, if you have a vacuum leak, something cloged, etc then a weber would run like crap too.

diagnose the problem, go from there, test equipment is there for a reason. Look up the list of problems that vacuum gauges diagnose, and the way to read them and hook one up.

2 turns is a starting point that will likely run, it may or may not be the proper setting, especially if there are other problems. I think mine is closer to 5 turns to run right, I started at 2 turns, kept backing it out to get better vacuum readings and idle. just turn down the idle to 700, turn out the mixture screw till it smooths out and the idle climbs, rinse and repeat till it doesnt help, then fiddle a little to get it perfect.

#21 ferox

ferox

    King of the Echo People

  • Members
  • 796 posts
  • Portland, Oregon

Posted 22 September 2012 - 01:26 AM

If those are the UFOs looking things, I took those off a week or so ago. It ran great until I messed with the bottom screw.

I could try to put them back on (like you said earlier) and "T" them together, if you think it has value


It will never run correctly until you get the fast idle screw adjusted properly. On the attached JPEG you want to try to adjust G1 into spec.

What is your timing set at?

Posted Image

Attached Files


Edited by ferox, 22 September 2012 - 01:29 AM.


#22 Gloyale

Gloyale

    It's a sickness

  • Members
  • 8,557 posts
  • Corvallis, OR PNW

Posted 22 September 2012 - 10:55 AM

If those are the UFOs looking things, I took those off a week or so ago. It ran great until I messed with the bottom screw.


See this is what I mean.

You don't know what emulsion tubes are. You don't understand carbs.

Do yourself a favor, and check out a carb theory book from the library.

You'll never get it right till you understand what it is you are doing. read my thread in the carb tech section for a bit of an explanation of how to remove the emulsion tubes and clear them out.

#23 Gloyale

Gloyale

    It's a sickness

  • Members
  • 8,557 posts
  • Corvallis, OR PNW

Posted 22 September 2012 - 10:58 AM

It will never run correctly until you get the fast idle screw adjusted properly. On the attached JPEG you want to try to adjust G1 into spec.


Fast idle screw only controls just that. How fast it idles when the choke is on.

after the first ten minutes of driving, it does nothing.

no effect on mixture, or changes to air bleeds.

You could remove the whole choke/fast idle assembly and it would still run great.

This is the last adjustment he should be worried about, unless he's having a cold start/ driving issue.

#24 Gloyale

Gloyale

    It's a sickness

  • Members
  • 8,557 posts
  • Corvallis, OR PNW

Posted 22 September 2012 - 11:01 AM

Soobiefreak85

If you can bring the car down here to Corvallis I can tune the carb for you very reasonably (depending on what type of beer you bring:brow:;):clap:)

Just give me a heads up when you wanna come. PM for my phone # and Address.

#25 ferox

ferox

    King of the Echo People

  • Members
  • 796 posts
  • Portland, Oregon

Posted 22 September 2012 - 02:00 PM

The two UFO things sound like the choke pull-off dash pots. If the choke is still installed, but not completely or correctly, and the fast idle screw is off-spec, then the car can die randomly and not be restarted if the choke engages after the engine is warmed up. Make sure the choke is also getting power to heat the internal spring. The car will run fine without the choke once it's warmed up, but the choke can also prevent the car from running if it is not functioning properly. I recommend reinstalling the dash-pots with the orifice restrictor in the vac line, confirm that the mechanicals inside the choke housing are oriented correctly (it can go back together with the cams and pawls mis-oriented), check that the choke gets switched power, and adjust the fast idle screw to spec.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users