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Hello I have a 1985 rx7 with the 12a. Every time it starts it needs the choke and jumps up to 5k rpm’s before it goes down to 3k to 4k and when the choke goes back in and it drops to under 3k it sputters and dies. I have done a rats nest delete but not sure I got everything figured out. Help is much appreciated
Before the delete it would again die under 3k so I decided to do a rats nest delete to see if it was a vaccum leak that was causing it. I took off the rats nest and capped all the lines from the carb and intake.
I tested compression on both housings and it stayed and held at around 110psi. I also took apart the distributor and it looked to be timed right(with the 1mark on the pulley lined up with the point, the arrow on the distributor was pointing toward the oil cap). I also took off the exhaust and ran open headers to see if the cats were clogged and was causing pressure but it still didn’t idle. I adjusted the mixture screw and turned it 4 times out after it was tight. The carburetor seems to be working correctly.
I checked over the carb linkage again and everything looks good. Right now I am running a cheap pump and regulator, one time it overfill the bowls and was leaking out at 2psi and then it was fine at 3 psi. I am not sure if this was just the floats sticking inside or if the pump or regulator is malfunctioning. Should I just get the right pump and get rid of the regulator or is the problem something else.
Not sure a new pump will fix this, but I always try to run a factory pump. The 1984/1985 pump is not available any longer but the 1981 to 1983 can be made to work. This is what I did on my 1985. The bends off the 1981-1983 factory Mazda pump are a little different. I've also ran a non-factory replacement and it didn't live very long.
Here is a video of it for you guys. I am new to rotary’s and know that they sound different especially with idling but it sounds off to me, but does this sound right?
From what I can see the linkages look alright for the most part. One arm is rather bent but that's not terribly uncommon on them as it's used to adjust the engagement point.
One thing that does stand out is that the dashpot looks like it's threaded in really really far. From the tiny bit I can see of the idle speed screw it also looks really far in, although I can't confirm that from your photos nor can I see the throttle blades in any of them. When adjusting the idle mix screw which screw were you turning?
The mixture screw is the one under the omp lines, and the idle screw I turned it 6 turns out from seated
Alright, well you've got the screws right which is good. I don't really suggest setting the idle screw by turns from seated. Rather, unscrew it until it's no longer contacting the linkages and then tighten it maybe a turn or two. The primaries should be barely open at idle.
Also I believe you said you set the mix screw at 4 turns out, that's full turns, correct? The factory baseline is 3.5 full turns from seated, but 4 works just as well as a starting point.
The next thing I'd check is the fast idle linkage since the engine is running to 5k (assuming for now that it's not a vacuum leak). This also assumes the butterflies are closing properly. When the choke is pulled the throttle should open just a little bit, take a photo of the butterflies at idle position and then the primaries with the choke linkage pulled.
I had a similar issue on a new to me 85. If you haven’t already done so, be sure to clean out those jets airbleeds etc. It took me doing that a few times as crud kept coming out of the fuel system.
Also had a bunch of junk stuck in the inlet outlet wire filters on the carb so could be worth checking.
I ended up replacing all fuel lines and made sure I didn’t have any vacuum leaks etc. Now the car idles and drives much better. Just wanted to mention those things since I couldn’t tell if you’ve already done that.
I had a similar problem, I was going to do a rats nest delete, but people here advised against it, and most said it was probably a vacuum problem, so I got a vacuum gauge/pump: https://www.harborfreight.com/brake-...kit-63391.html, and checked the vacuum system everywhere I could and it seemed pretty tight, so then I blew smoke at the top of the engine and hoses while it was running with the choke on and the leak seemed to be coming from under the carb so I pulled it and checked all the hoses there with the vac pump, then put the carb back on making sure it had a good seal and then it ran good after that. that's the best I can remember anyway.
Hello everyone, I’m here with an update. I took the carburetor completely apart and got it ultrasonic cleaned, I put it back together and it idles!!! The problem is it starts at 500rpms and slowly works it ways up close to 2k where it holds steady. Looking down at the carburetor there is a little bit of gas dripping out but the bowls are only half full and don’t see to be overflowing. I think this is the cause. Any suggestions? Attached is a video.
10-31-22, 11:33 AM
