Need help tuning carb!!!! please!
My dad and i just rebuilt my carburetor using the mazda rebuild kit. After about 4 days of toying with it we finally got it put back together and back on the 7. Although there is still a few things we cant figure out. I have a hayes manual and it doesnt address the problems either.

Note: this is the 4 barrel 84-85 12a carb. Manu. trans.

1. Below the Fuel send and return is a large vaccum line. Below it and to the left is a much smaller line. That we dont have a hose for. I cant find any digrams of what this line is for, or what goes to it. The vac. line going to Sub-zero assist thing. is open also because we cant figure out what goes to that either. (guess we should of payed more attention when we were taking it all off.) We tried to squezze that house on there, to seal the vaccume but it is a little larger.

2. After we got some fuel up to the engine and got it running, i pulled the choke shut and let it warm up. but you really have to watch the idle because it is not steady at all. it might run for a few seconds at 2-3k. but then it seems like it loses vaccum and will drop to zero. But if you slam down the gas, it might come back up.

the book is pretty vague on how you are suppose to tune this thing. So if anyone can give me any help i would greatly appreciate it. Also, where can i find some better diagrams of the vaccume system?

Thanks,
Shawn

 

you might find something on www.iluvmyrx.com

when it cuts off is it hard to restart, like it may be flooding or does the fuel fall below the sight glass?

peace

 

get your vacuum hose issue straightened out before attempting to tune the idle. here are some pics that might help.

 

stupid internet stalled........

 

2nd pic. this is a 79 carb so there might be a few differences.

 

I cant really see into the sight glass, but the jets do still spray plenty of fuel. After it cuts out, you can start it up just as easy as usual. which does require to give it some gas as you turn the key. Its like its trying to go, but something else is trying to shut it off at the same time. thats why we think its a vacum issue.

 

Ill search thru my pics tonite and see if I can find my rats nest pics (RIP) j/k

peace

 

Thanks jeremy, youve always got an anwser for me. This hose i colored red. Where does it go to? i think that might be it.

 

Mine is back together but not starting for a different reason. If you don't have your answers by tomorrow afternoon CST, I'll post how my stock '84 GS carb is set up with some rat's nest detail shots as well...

 

that is the sub-zero start assist.

 

oh yeah and i pmed you. i'm coming up to louisville saturday to start a new job monday.

 

Hey Jeremy, we got an AutoX Sun. the 25th, me and james should both be there. If you aren't too busy you should come by. Its at Cardinal Stadium.

www.kyscca.org

 

i will hopefully be racing in it with you. thats is if i can scrounge up an entry fee.

 

Awesome, are you going to be living here? i dont know why but i dont have any PMs. email me.

 

Hey Maguire, this past weekend I rebuilt my 80 carb and it's doing the same thing and also yesterday I got it to run at 900 rpm can't go lower it shut off. So 900 rpm it's and as soon I put back the air intake it shut off and it started to the same problems like yours is having also my vaccum is correct so I don't it's your vaccum and the sub zero is for very very cold weather starting {Alaska}. Also what year carb u? Because below the accelerator cable there is a throttle screw which need to be adjust {after the idle speed is been tamper with} according to mazda shop manual. good luck let us know what u find to solve your problem, khris

 

Its good to know that im not the only person that has had this problem. Tonight we worked on it some, we checked all the vaccum hoses, they all seem to be going to the right places. So it must have something to do with the adjustments. Or something internal. When we closed the choke all the way after it got a little warmed up. It would run steady, but at about 2500rpm. If it got under about 1800, it starts to jump, jerk and then no matter how much you pump the gas it ussually dies. although when it is running at 2500rpm the accelerator does function.

rx7aholic, My carb is an 85 so its slightly diffrent than yours. Did you ever get your fixed? I wish i had another car to look at so i could see if im missing something. Where can i find a blown up picture of the whole intake/fuel system?

 

Where exactly in Louisville are you? I live very close to Churchill Downs. If you want, I'd be happy to take a look at it if you want me to. If you can, come out to Cardinal Stadium this Sun. and look for a loud silver 1st gen. My name is Joe, #12 CSP.

 

If you would come help me out that would be the best thing in the world. Im so tired of fooling with this thing. I actually consitered towing it to tachyon just to get it running. I live on 6th on ormsby. Thats about 15 minutes from 10 minutes from chuchhill downs. Email me when you get a chance. Thank you soo much.

Shawn

 

i pmed you. i'll be in jtown right off tailorsville rd. in a complex named boulder creek. they say your not supposed to work on cars in their lot, lol. i'm going to be in so much trouble.

 

Hey Jeremy, remember to pre-register at www.myautoevents.com

If you don't pre-register, you have to get there before 9 to register on-site, or you can't run. If you get pre-registered you have till 10 to show up. Hope to see you there, I'm pretty sure James is coming too.

And Maguire, I'll probably be pretty busy getting my car ready for the AutoX most of this week (my carb is leaking fuel ) But next week I hope to be free. I usually get off work about 5:30-6, and am free most Saturdays. Let me know whats best for you and I can get all my Rex buddies together to come revive a 1st gen

 

Jeremy,
I used to live in j-town right next to the rail road tracks off of taylorsville. But now i reside in old louisville. If it is the place im thinking of right next to the train bridge, then i dont think they stand by there word to much. Theres was always a broken down camaro or some junk sitting in there parking lot.

joe,
Thanks for the offer. I just found a mazda parts manual on iluvmyrx7.com, its the same exact thing they have on microfilm at the mazda dealer. It might be helpful. So im going to continue to work on it and see if i can figure anything out. If i cant, ill let you know something this weekend. maybe ill find you at the autox if i go.

Thanks, alot,
Shawn

 

Hey Maguire did u found your porblem? ANyhow I found my problem I brought a 3 carb from a Rotary shop and and they are 83-84-85 carb. Anyhway I took the 83 apart and rebuilt {not complete run out of gasket} and I notice something with the 83 float where the needle is the is a small silver locking spring which hold the float at idle, now my 80 did not have that because the guy I brought the car from play with the carb and did not put back everything together it suppose to be and the rebuilt kit does not give u every detail. Now back to the 83 carb I rebuilt the 83 half way and put it back into my 80 and the car start up and the choke hold at @ 2000 rpm for 3 minute for warmup, like it should do according to the mazda shop manual. Also after it warm up I fine tune it and set the idle to 750 rpm according to the book. Also now I can start the car from outside. So look into that before U go carzy. Also does your car smoke after 10 minute running {too much gas} running too rich? let me know If u still need more help? ALso when u fine tune the carb u need to removed the gas cap and plug one vaccum line that goes to the air intake cover it'sa the bimetal vaccum line.

 

No i havnt looked at it in a couple of days. I've been doing as much reseaching as i can. I think it might have too much fuel pressure, but i dont know how to adjust that. I did drive it out of the drive way and around the block to get it out of the way so my dad could do some suspension work to his miata. When i was driving it i did do i few very peciular things. for one, when i could get it to idle it would stay at about 2800-3000rpm. But it had abosolutely no power at all. It would almost stall when i shifted gears, at 3k, at about 20mph. i dont fully understand this. And two, i know that there isnt a vaccum leak because before we rebuilt the carb by breaks were very very very weak. If i breaked to fast it would stall at idle, expecailly if i pumped them. And when iwas driving it down the alley, on wendesday the breaks were stiff as a board. i didnt do anything to them, so that was obviously a leak.

Do you know how to adjust the fuel pressure? Thanks for the advice on the spring, ill check and make sure that it is still there.