dr_hunt Posted December 10, 2004 Share Posted December 10, 2004 Sounds like a classic sick quadrajet. This is a very simple carb that few people understand or comprehend. Correctly built and tuned it is a fine performance carb for the street. A completely stock rebuild should get you to where it starts and runs without touching the accelerator pedal or pumping it once to get it started. If you are going to build it yourself disassemble it and completely immerse the carb parts in carb cleaner for several hours or longer depending upon condition. Rinse thoroughly and blow all passages with air. Make sure you remove the air valves in the base plate and blow those as well. Some come sealed, which can still be removed if you drill out the plug. Standard settings on the air valves is 3.5 turns out from lightly closed. Set float level at rebuild specs and use a brass float. Since it is not on an original engine, tuning is going to be required. Adjusting primary metering rod height is critical for cruise enrichment as is the proper primary metering rods. Secondary cam, rod hanger and rods need to be selected based on the plug readings and any hesitations, bogs, etc. The secondary air valve is controlled by a spring that is adjustable. I think it is 1 turn for SB's and 1.5 turns for BB's, but that is stock and you can adjust it from there to remove stumble caused by premature opening of the secondaries. Quote Link to comment Share on other sites More sharing options...
Savage42 Posted December 11, 2004 Share Posted December 11, 2004 I'm not a Quadrajunk fan, have always gone with Edlebrock performer carbs. (now I'm going EFI, of course) Sounds like the choke could be funky. Manual or auto choke can make a difference. If the car sat long enough for the battery to go dead for any amount of time, the fuel in the carb could have turned into varnish or the carb just needs to be cleaned & rebuilt. Nothing major, just a little time consuming but well worth it when it runs right. Congrats on the new ride! Quote Link to comment Share on other sites More sharing options...
Sleeper-Z Posted December 11, 2004 Share Posted December 11, 2004 you should prime the carb before starting, not sure how it is on a mechanical fuel pump. but depress the gas pedal fully about 2-3 times before starting and try starting without getting on the pedal, that should help without waking up the neighborhood everytime you have to go somewhere. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted December 12, 2004 Author Share Posted December 12, 2004 Thanks all, I'll try the pedal pumping first since it's easiest to do, besides, I don't fully understand carburetors yet, let alone doing a complete takedown/rebuild. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted December 20, 2004 Author Share Posted December 20, 2004 Hi again, Today I tried to start the car again with the air filter removed. The car won't start despite [pumping gas prior to start] or [pressing the pedal while turning the key] (Last time the engine will run continuously as long as I [depress the gas pedal about 1/4~1/2 while starting] and then [keep a bit of pressure on the gas pedal]...see previous posts.) So today I was sitting in the driver's seat, cranking the engine trying to start....then I saw a bit of flame shooting out of the exposed Q-jet, I stopped immediately because I knew I didn't have a fire extinguisher handy. The flame is more like a flash in the pan, lasted very short(about 0.4 sec?) and it stopped as soon as I stopped my actions. I then went to examine the carb(not a smart thing to do when your carb was shooting flame 10 seconds ago, but I didn't care if I lose my eyebrow) , I pulled the throttle cable, primaries opened and steamy gasoline vapor came out of them. I looked past the throttle opening (into the manifold?) and there was liquid inside, I guess I flooded the damn thing again. But why is my carb shooting flames? ----------------------------------------- This is a brief timeline of incidents : Mid November : Ex-owner drove the car to train station to have the car delivered. 13 days later : Car delivered to my house on a truck, the delivery guy started the car and back the car into my driveway. THE VERY NEXT day : I can't start the car, battery was weak and then died from many starting attempts. May have flooded the engine. 10 days later : Removed spark plugs from all chambers to let the cylinders dry. Removed battery for overnight recharge at an autoshop. 3 days later : Re-installed spark plugs and battery. The car will start if I depress gas pedal while I turn the key, however the car will NOT stay running if I take my foot off the gas pedal. 10 days later (today) : Try to start the car again with the air cleaner removed. There were some brief moments when I hear the engine roar but it never did ran on its own. Then I saw flame coming out of the exposed carb and I stopped. Steamy gasoline vapor came out of the primaries after I yank the throttle cable. May have flooded engine again. -------------------------------------------- Some discoveries about the fuel system : 1. On the pump-to-carb duct there is a transparent plastic cup with a filter inside, you can see if there's fuel in it. Over a long period of time(like 10 days), the fuel level in the "transparent cup" recedes. Turning the engine will bring the fuel level up quickly(of course, the fuel pump pumps it up). I don't know if the receding fuel level has any bad effect on the carb because even with the cup empty, squirts of gasoline shooting into the carb can be seen and heard with every pedal pump. The fuel ducts seem to be good, not cracked because when I squeeze the plastic cup a bit I can always hear a tiny hiss coming from the carb. 2. The long rectangular valve on top of the primaries (is it the choke valve?) ....someone before me stuffed a section of tubing into the choke control arm slot to keep the choke open at all times. Since it's intentionally done for a certain reason unknown to me, I left it that way. ------------------------------------------------------------------------ What puzzles me the most : What puzzles me the most is the fact that the delivery guy, knowing nothing about the car, fired the car right up after 13 days of inactivity, backed into my driveway, got out of the car, and the car stayed running. On the very next day it won't start, then battery ran out of power . 10 days later I installed a completely recharged battery and the car will start but won't keep running unless I kept my foot on the gas. Another 10 days later the car won't start at all. I have not changed any settings at all, whether it's the carb or the car itself. Gents, I appreciate your help, I am in an embarrasing(I've only driven the car for 3 feet in reverse) dead lock here. The auto service shop I usually go to won't even deal with carburetor cars, and they refuse to come over to do diagnosis. I just received 2 books on Rochester carburetors(one by Doug Roe, and another from Haynes), I'll read as much as I can once finals exams are over. It's very frustrating, but I know many years later I'll look back at this and laugh, afterall, who's going to forget his first Q-jet diagnosis if it ended up with flame shooting out of his Q-jet? Quote Link to comment Share on other sites More sharing options...
Sumo Posted December 20, 2004 Share Posted December 20, 2004 If flames are shooting out your carb, check your wires for the correct firing order. You may have inadvertently switched a couple of wires when you took out the plugs. That's all i can think of for now unless you skipped a tooth on the timing chain which is doubtful but probable. Hope it helps. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted December 20, 2004 Share Posted December 20, 2004 Thats was what I was going to say. I did that once.. reversed the firing order ..well.. put every plug off by one location on the distrubutor. (Basicaly, instead of 1-8-4-3-6-5-7-2, I had 2-1-8-4-3-6-5-7) Oops.. had some good flames leaping out of the carb!! You may want to check out the distributor cap and rotor.. they may be in need of replacment. I think the choke could be causing part of the problem though.. Even though it may be a mild temperature outside (for people I mean) it's still a 'cold' start for an engine, if only for the first few mins. Just from my expiriance with my backyard built RX7 V8, I had to play with the gas a bit to start it up and keep 'bliping' the throttle a bit till it warmed up. I never had a proper choke setup, but it was the middle of the summer and warm up would take about 2 mins so I just delt with it. Just curious.. have you contacted the previous owner? Not saying he 'screwed you' but if he drove/built the car he may have some advice for you, or a better idea what 'may' be going on with it. My 75 is pretty stock, but if I sold it I'd have to spend a good 2 hours explaining evrything to the buyer.. how this works, what to do if, ect. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted December 21, 2004 Author Share Posted December 21, 2004 I read your comments about firing order and choke, and went to check again. I followed the distributor cables and it was correctly installed. I did make sure the lines go back to their original places when I pulled the plugs last time, but who knows? I checked it anyway...nothing wrong there. Then there's the choke, I just read about chokes in the carburetor book yesterday and what it told me was that choke is really important for start-up. After finding no error in the firing order, the rest of my hope went into freeing up the choke valve. I pulled the piece of rubber tubing out of the choke control arm slot to free up the choke...I expected the choke valve to shut immediately once I freed its movement, it didn't, then I yank the throttle and the choke valve shut right off. With the choke on I went into the car and tried to start it without air filter and without pumping the gas pedal. Two tries and it fired right up. YES! I left it running for 5 minutes and then I turned it off, put air filter back on and tried again. It's like she wanted to start !!! When I finished working on the car the sky cleared up and the sun actually came out, it was beautiful, lol. One question about the choke though....when will it fully open? I left the car running for 5 minutes and noticed no change in its position...it stays slightly open. I thought the engine heat will open it up but it didn't. I thought the vacuum break will open it up....it didn't have any effect even when I was revving the engine. I've yet to actually drove the car on the road. Do I have to put the car in gear and drive it for the choke to open? If the choke is having trouble resetting itself to a fully open position, maybe that's why one of the ex-owners had the choke stuck open intentionally. Thanks for all your help, she's alright for now. All that much trouble from a tiny piece of rubber tubing. Quote Link to comment Share on other sites More sharing options...
Sumo Posted December 21, 2004 Share Posted December 21, 2004 It sounds like that the previous owner kept that tube because that's how he set the choke. After running it for 5 minutes when it's warm, try holding the choke fully open with a paper clip or piece of wire and see what happens. All this trouble your having could be just because of a faulty choke. What model Q jet does it have on it? Quote Link to comment Share on other sites More sharing options...
waynekarnes Posted December 21, 2004 Share Posted December 21, 2004 glad to hear you have 'er running ... always a thrill ... when the car was backed in, a bit of dirt may have gotten in a jet, plugged an orifice, has since worked out ... pumping the blank out of the carb, should have shot enough fuel in there to get it started, even without a choke, feathering ( lightly running the gas pedal up and down ) the gas should of kept it running. but, you are correct ... no choke, runs lean, misfires ... pops out the carb ... so you have the manifold heated thermostat or electric ??? manifold heated, would have two tubes circulating heat from the intake manifold ( conductive heat from the exhaust of the engine ). the electric has a metallic tab sticking out from the side of the carb, for 12 volts to attach to ... both sort of work the same way ... coil of wire ( like spring in a watch ), heats, and causes the choke to open. as long as all is fine ( i've seen where a fool, knowing little enough about carbs, has removed or broken the spring or retaining tab, that holds the spring ), anyway ... on the side of the carb ... grab your book ... on the side of the carb, you will see a black disc, has incremental lines drawn on it ... with a line up the middle ... one side says rich, one says lean ... you can loosen the 3 screws around the outside of the disc ( engine warm), and adjust the position of the choke, so that the quadrajet is actually one of the best carbs ever made and one of the worst ever understood. i surely don't claim to be an expert ... i own books ... i read, i ask those who have been there before. the quad works off of the amount of air the engine needs, unless it's jetted wrong, it's hard to over or under carb with the quadrajet ... my understanding is, it is a close to fuel injection as one can get with a carb. check out this web site ... you may find it useful ... http://vetteworks.tripod.com/Qjet.htm this site is much more involved, but if you have a q jet, you'll benefit from reading the info there ... http://www.442.com/oldsfaq/ofcrb.htm#Carbs you may want to bookmark these sites ... GM had been using the Q jet for years, before replacing em with F.I. they don't spend money year after year, if it's gonna cost them money fixing em .. holleys, carters, are all good carbs, most edlebrock's are reworked rochester carbs, the big spreadbores are reworked q-jets ... i'm running a edlebrock performer 795 cfm on my 350 chevy. it's a reworked q-jet. Q-jets are more complicated for the back yard mechanic to figure out. holleys are fairly simple, and now that they have better throttle body valves ( don't shrivel and die after a backfire and flood your engine, as easily as they used to ), they are a good choice for the novice. but it's hard to beat a good running q-jet for overall performance and gas mileage. grab the HP q-jet book, and with a little experimentation ( changing metering rods, ect ), you can have a kick ass carb set up. good luck with it ... glad Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted December 21, 2004 Share Posted December 21, 2004 This might be kind of off the wall, but you said... "I got my Chevy 383ci V8 240Z couple days ago. My first American V8 car, also my first carbureted car. I asked questions about the car on my first post here :" (dead link) So tell us where this car came from. Did it sit for a long while? Has it ever ran right? Did you test drive it? Who did the swap? Can you tell us what kit it was or how it was done? How about Carb type, fuel delivery (Electric or Mechanical) set up and ignition type? Sounds to me like you got it, Tried to fired it up, it back fired and died, and stayed dead. My first instict is that it flooded and you killed the battery trying to start it. Why did it flood? You said you might have touched the peddle but don't know. The reason I'm asking is when I put my Carbed v8 it did similar things with starting and flooding and deing. If it ran at all it ran like crap. Turns out I needed fuel pressure regulator. By the time I got that figured out and installed I had to replace my Quad carb because too high pressure had blown out some gaskets (Accel pump). I'm sure it wasn't in too good of shape before hand, but it did run in the vehicle it was in before. - Just a thought. Oh, and I was never much of a car guy until I bought my Z. Five years ago I hadn't even changed a starter on my own. Once you master the ability to read and understand a Haynes book, you can do anything. (Especialy when your model car is mentioned as an afterthought in the appendix.) Anyway, I think Zs have brought alot of people into the "Car Guy" world. Welcome, you are now one of us. You said... I've only became interested in cars recently, few months ago, before that, I don't really know anything about cars, I dont' know much now neither. Now I read about car stuff everyday if not too occupied by college work. What I am reading now is a book by David Vizard, "How to build max performance small block chevy on a budget." Very good book, now I got the V8 it's even better. I also read tech magazines, and have several maintainence books, they usually help, but not always. ... See you already got what it takes. Just go buy a good v8 Chevy book, a Haynes for the Zs, and what ever other technical book that might have something to do with your car or parts. (ie. If you got a camero motor get a Haynes for that, if you got a Holley Carb, MSD Ignition whatever.) -Tony Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted December 22, 2004 Author Share Posted December 22, 2004 Thanks for the replies, to answer some of your questions.... The choke : After letting the engine ran for 5 minutes that day, I actually got out of the car to mess with the choke valve. The engine ran with a higher rev and a sharper sound if I flip open the choke valve. That probably means the engine no longer needs the choke and the choke is robbing power and stealing gas. The choke is mechanical...I don't recall seeing any electrical wires going into it. Maybe the choke is not opening because thermostat coil is not getting exhaust gas...I'll have to check again. Tony...the car starts fine now, I just got to figure out how to make the choke reset to full open. The car had start-up problem because one of the ex-owners intentionally stuck the choke open. "Once you master the ability to read and understand a Haynes book, you can do anything. (Especialy when your model car is mentioned as an afterthought in the appendix.) " Heheh...that basically speaks for all 280Z owners, the Haynes manual includes 280Z as a model but it only has info on 24Z & 260Z. Thanks again Quote Link to comment Share on other sites More sharing options...
Sumo Posted December 22, 2004 Share Posted December 22, 2004 Buy a new Qjet with an electric choke, it will make your life simpler. If you buy another brand like Holley make sure you buy an adapter because the bolt patterns are different. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted December 22, 2004 Share Posted December 22, 2004 Or get the mechanical choke kit and put a bif frickin spring in it like i did. If mines sticks it'll be stuck open!! Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted December 23, 2004 Author Share Posted December 23, 2004 I am not familiar with getting replacement carburetor parts. Any website/place where I can order replacement parts for Q-Jet? Thanks Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted March 29, 2005 Share Posted March 29, 2005 Just so I don't have to start a new thread...I'll post in this one... Sometimes (most of the time) when I go to start my Z (350 with a Quadrajet) fuel actually spits out of the top the carb...then I gotta pump it a couple of times to get it to start. Once it start it *seems* to run ok...maybe slightly rough, but, I don't know if that's because I'm still running through open block hugger headers. Never owned a carbureted car before, but, I wouldn't *think* this is normal...is it? Or is it because of the electric fuel pump forcing fuel into the carb during startup? Confused in Arizona. (note, while running it DOES NOT spit out fuel from the top of the carb) Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 29, 2005 Share Posted March 29, 2005 The Need for Z The choke is mechanical...I don't recall seeing any electrical wires going into it. Maybe the choke is not opening because thermostat coil is not getting exhaust gas...I'll have to check again.Mechanical choke will have a cable that runs into the car which one can pull to force the choke to close during start up. Releasing this and the choke opens again. Mechanical Chokes rarely get stuck, unless your return spring breaks. This is why I got a mechanical choke.Tony...the car starts fine now, I just got to figure out how to make the choke reset to full open. The car had start-up problem because one of the ex-owners intentionally stuck the choke open.If the ex-owners intentionally stuck the choke open, it was probably broken first. Re stick it open for now. (zip ties work great) and just pump the gas a bit when trying to start it. My advice at this point is drop some cash on a good new carb. I bet you'll be so much more happier with the car with a good dependable carb on there. (I think I already gave you this advice) "Once you master the ability to read and understand a Haynes book, you can do anything. (Especialy when your model car is mentioned as an afterthought in the appendix.) " Heheh...that basically speaks for all 280Z owners, the Haynes manual includes 280Z as a model but it only has info on 24Z & 260Z.Look at my signature. The 280z is discussed only in the appendix of the Haynes manual. They cram all the new EFI stuff in one little chapter and treat it as though you should already know this. This is one reason 280s are treated as the bastards of the Z cars. And if you own a 2+2... you get no respect. awd92gsx Define "spitting out the top". Like a steady stream spraying? or dripping down the sides? Where at on the top? Does it "spit" constantly? Or only when you move the throttle lever? As a general rule, fuel coming out of places that it shouldn't be is a sign of too much fuel pressure. That said, do you have a pressure regulator for your electric pump? Accurate and reliable fuel pressure guage? (Autozone cheap-o gauges are junk IMO) How much pressure are you pushing? Too much or Too little pressure will make it run rough. What I'm picturing is the fuel coming out of the accelerator pump. Back when I had a quad and an electric pump I had too much fuel pressure. I had fuel leak out of the accelerator pump. I ended up ruining that carb from too much fuel pressure before I got a pressure regulator on there. I assume it is the same situation with you. If it is "spitting" it sounds like you got way too much pressure. Need more info to diagnose further. Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted March 29, 2005 Share Posted March 29, 2005 Hmm...now that you mention it there is a little bit of fuel seeping from the accelerator pump. Now, it's while cranking basically...it just shoots a jet of fuel right out the top...maybe I'll try the fuel pressure regulator...I'm not sure of the fuel pressure, but the pump was rated for 5-7psi @ 35gph, doesn't necessarily mean it's not putting more than that out, though...especially since I rewired my fuel pump with something like 8 guage wire and a relay setup. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 29, 2005 Share Posted March 29, 2005 it just shoots a jet of fuel right out the top !! ...?? ... ... Can you identify the part of the carb it is spraying out of? How high is this jet of fuel? ...maybe I'll try the fuel pressure regulator...I'm not sure of the fuel pressure, but the pump was rated for 5-7psi @ 35gph, doesn't necessarily mean it's not putting more than that out, though...especially since I rewired my fuel pump with something like 8 guage wire and a relay setup.Yeah, sounds like my problem all over again (without the jet spraying carb.) I trusted the rating on my pump also. WRONG !! Get a pressure regulator on there. Jegs sells them pretty cheap if you are ordering other parts to make the 8.99 shipping worth while. I hope your carb is not shot (as mine was) but a fuel spraying carb is definatly not safe. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 29, 2005 Share Posted March 29, 2005 I've only became interested in cars recently' date=' few months ago, before that, I don't really know anything about cars, I dont' know much now neither. [/quote'] You sure picked a good one to start with... I say this both honestly (Z's are great cars, easy to learn and work on, and same goes for small block Chevy engines... don't get much more basic than that) and semi sarcastically, because... well... to learn cars with someone elses already-done or mostly done project... can really be the hard way to do it. Though there are actually books written on the SBC swap into a Z... they aren't usually done 'by the book' or at least, not w/o a lot of variances. The problem is the only real, 100% accurate source of knowledge on that car will be the person or persons who did the conversion... there are no Haynes/Chilton manuals for hybrid Z's.... Luckily you have these great guys here on the forums so chances are you wont ever really run into a problem that SOMEONE wont know where to look or how to fix it.... but still... I wouldn't want that to be the first car I learned about cars on.... Quote Link to comment Share on other sites More sharing options...
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