torxxx Posted February 10, 2009 Share Posted February 10, 2009 rebuild the top end of the carb this weekend, did the needle replacement, couldnt get the brass seat fitting out of the top of the carb though it seemed to be seized in there. Set float lvls according to rebuilt kit specs. I did leave the lil metal clip deal off the top of the seat because it interferes with the float movement, and I talked to chevy carb gurus about it and they said that piece is just in there to hold the needle in place until after float settings are made. Car runs like a raped ape now, but its still running rich at idle because of this fuel dripping problem. I gotta get this fixed cuz its killing mpg. Please post up. I am pulling the top off my spare carb and I am going to put in the vent tubes and the rest of the stuff into this one, see if this helps it at all.. Thanks in advance Link to comment Share on other sites More sharing options...
naru Posted February 11, 2009 Share Posted February 11, 2009 How high is the fuel level in the sight glass after sustained idling? Link to comment Share on other sites More sharing options...
subiemech85 Posted February 11, 2009 Share Posted February 11, 2009 leave the needle clip ON, it is more important than you think!! I don't care what the fuel level spec is in the instructions, and measuring it is too damn hard, 18mm to what to set fuel level bend tab that needle contacts fuel level is set to the beveled area about 1/2 way up you will see where it transitions from narrow to "slightly" wider on the back wall by the hinge, IIRC set the fuel level to this point, then install gasket and 2 screws to see if fuel runs out! BTDT lats saturday!! also, it is not necessary to have a hollow bolt, a solid one will do just fine the seat did not want to come out Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 11, 2009 Share Posted February 11, 2009 So fuel is dripping from the main nozzle into the primary venturi during idle correct? One of these is true: 1. Throttle plate is not fully closed. 2. Blockage in the air corrector or emulsion tube. 3. Float level too high. 4. Float needle is not sealing. 5. Fuel pressure is too high. GD Link to comment Share on other sites More sharing options...
torxxx Posted February 13, 2009 Author Share Posted February 13, 2009 GD I'ma lower the float lvl some when I install the other top off my spare carb. I got the brass seat out with a blow torch lol. I did some fiddling around with the vac lines and vent crap and got it to run a lot better, but it wont idle unless the screw is ran into to about 1400 RPMS Getting tired of these carbs.. might just buy a SPFI wagon and put my list and mods on it Link to comment Share on other sites More sharing options...
monstaru Posted February 13, 2009 Share Posted February 13, 2009 try the anti diesel solenoid.....it is directly hooked through the idle circuit.if the wire is loose at all it could be making the carb ACT funny.at idle,at full throttle,etc...cheers, brian Link to comment Share on other sites More sharing options...
torxxx Posted February 13, 2009 Author Share Posted February 13, 2009 yah I was looking at changing that because its started to diesel now when its warm.. getting so tired of this car.. been nothing but a money pit the last 3 months.. thanks for the advice fellas Link to comment Share on other sites More sharing options...
Frank B Posted February 13, 2009 Share Posted February 13, 2009 It's been too long since I had a Hitachi apart to remember, but do the auxiliary venturis come out of the Hitachi? If so, there may be a small o ring between it and the inner bore. Use this Weber diagram to see what I mean. http://www.piercemanifolds.com/carbdetails/explviewparts/32_36_DFEV.pdf I'm saying this because I had a similiar problem with a Holley 5200 and the O ring was flat, hard, and not sealing. But it may be something as simple as a warped carb body. Take it back apart and this time put a straight edge(metal ruler) acrossed the gasket surfaces, if it's warped you'll see it. If so, completely break it down, flip it over and do figure 8's on a piece of FINE emory cloth(sandpaper for metal). Make a couple passes and flip it over, you'll see how the outside edges are sanded clean, but the inner area is not, go just untill the inner area is shiny like the rest. You don't want to take off any more than you need to. Thoroughly clean the carb body and re-assemble. It may not be perfect, but it will get you by. Or double up the gasket. Link to comment Share on other sites More sharing options...
subiemech85 Posted February 13, 2009 Share Posted February 13, 2009 GD I'ma lower the float lvl some when I install the other top off my spare carb. I got the brass seat out with a blow torch lol. I did some fiddling around with the vac lines and vent crap and got it to run a lot better, but it wont idle unless the screw is ran into to about 1400 RPMS Getting tired of these carbs.. might just buy a SPFI wagon and put my list and mods on it IT WILL IDLE after the ADS works!!! BTDT!!! ADS will default so that the idle passages are blocked off to prevent idling and dieseling you CAN defeat the ADS by removing the plunger when everything is working, it should be able to idle @ 400 rpm, SMOOTH, mine does if you want, I can post pics of the carb vac. line system I am using with good results Link to comment Share on other sites More sharing options...
Svengouli7 Posted February 14, 2009 Share Posted February 14, 2009 subiemech-- pls post your vacuum set up. I was reading this thread as I have just rebuilt a hitachi and did ok, but am axing all non critical lines.. As Frank B suggested there are o-rings where fuel enters into the venturis.. set screws on opposing sides fix them in place. Couldn't hurt to check.. Link to comment Share on other sites More sharing options...
autopia Posted February 15, 2009 Share Posted February 15, 2009 I've also got a hitachi carb (dch340 on a different car) and guess what?......It's also dripping gas at the primary venturi/nozzle. The symptoms are the same: can't idle except at very high rpm. I disabled the anti-dieseling-solenoid (removed the plunger) and it had no effect. The fuel bowl level is ok and I also haven't located any externel vacuum leaks yet. Any ideas? I'd like to eliminate the simple stuff before rebuilding the carb. thanks btw - I've been driving with one foot on the gas and one foot on the brakes when coming to a stop......hope I'm not the one behind you at a stop light. Link to comment Share on other sites More sharing options...
DR DLEX Posted February 16, 2009 Share Posted February 16, 2009 check the slow-jet.Its under the brass cap behind the acc. pump.The litte hole at the bottom is most likely clogged.Also,while the jet is out blow back through the hole to back-blow the primary circuit.I use a clear BIC pencase,the taper fits inside the hole.This 5-min fix works great for me. Link to comment Share on other sites More sharing options...
autopia Posted February 17, 2009 Share Posted February 17, 2009 Thanks Dr Dlex - you're on to something! The hitachi dcp-306 on the subaru is somewhat different than the dch-340 on the isuzu. The slow-jet is inside the air-horn/throat and not accessible w/o removing the choke/air-horn chamber. Nevertheless, there were 2 air bleeds I could spray with carb cleaner: the primary main air bleed jet and an adjacent hole which appears to be another air bleed - maybe for the slow jet. Anyway, squirting either of these forced cleaner out the other as well as out the primary venturi nozzle (so they're all connected).....and, and......it can now idle again at a low rpm. The venturi nozzle is dry at idle (as I think it should be) but at higher rpm (open throttle) the venturi nozzle is now mostly passively spraying gas but still dripping somewhat, although not nearly as badly as before. Maybe I just dislodged some dirt/obstruction a bit. I'll next try removing the idle mixture screw and the anti-dieseling solenoid so I can spray and/or apply vacuum to all the primary passages and see if that clears any dirt. I'm assuming that the venturi nozzle should never drip (only spray) under all rpm/throttle openings. Is this right? thanks! Link to comment Share on other sites More sharing options...
Frank B Posted February 17, 2009 Share Posted February 17, 2009 I'm assuming that the venturi nozzle should never drip (only spray) under all rpm/throttle openings. Is this right? thanks! Yes, just a fine spray. the fuel needs to be atomized to burn. The very fine mist increases the surface area of the fuel, allowing more vapors to be created, and burn. Liquid gas will not burn, just the vapor. It's kind of like starting a fire in a woodstove, if you toss a big log in it, it will not catch flame. But if you were to split that same log into 50 pieces of kindling, it will flare up and burn hot. You really should have cleaned all passages when you had the carb apart. Link to comment Share on other sites More sharing options...
torxxx Posted February 17, 2009 Author Share Posted February 17, 2009 I cleaned out the vent tube on the primary venturi when I tore the top off. I didnt want to get too into tearing it down cuz it was on a sunday, had my kid at the shop with me. I will pull mine in the shop today and pull out the air bleeds and blow some air through them and clean the bleed jets.. see if that helps.. Kinda wondering if its my power valve not fucntioning properly is why its leaking? possible? Link to comment Share on other sites More sharing options...
autopia Posted February 18, 2009 Share Posted February 18, 2009 Yes, just a fine spray. You really should have cleaned all passages when you had the carb apart. Thanks. I suspected that even a little dripping was too much......but just had to ask...... Actually, I was able to get to some of the primary passages w/o taking the top/choke-chamber off. It's my daily commute chariot so I can't tear it apart and really clean it up until the weekend. BTW - Now that it's idling at low rpm ok again, I noticed that the idle mixture screw no longer has much effect - even when lightly closed it will still run (although barely) whereas it should really sputter to a stop. Maybe this is somehow related to the primary venturi nozzle still dripping a bit - but I can't explain it. thanks Link to comment Share on other sites More sharing options...
Frank B Posted February 18, 2009 Share Posted February 18, 2009 You may have to adjust the idle speed screw, close the throttle plate a bit. It may be open too much and running off of the primary venturi, instead of the idle circuit. It's a balancing act, and by the time you get it right, you may be ready to toss the carb acrossed the shop...... Link to comment Share on other sites More sharing options...
torxxx Posted February 19, 2009 Author Share Posted February 19, 2009 tore the top back off cleaned the passages installed a different top off another carb on it. Idles smooth as hell now, still drips a bit but runs 100% better Link to comment Share on other sites More sharing options...
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