Mark79

Hi,
My 1979 is having problems. Shop tells me the carb is bad and they can not rebuilt it, or at least no success so far. The vehicles runs with choke on, when the choke is off, at idle it dies. I thought it might be a clogged fuel filter or water in the gas, it sat over the cold winter in my garage for a few months.
My question for all the SME's, advice? Should I send the carb out to be rebuilt? Where to shop for a replacement? or could the problem be something else and we're focusing in the worng place? Just want to be sure, before I take the next step.
I am the original owner, this is the 1st major issue I have had... any help would be greatly appreciated!
Thanks in advance.
Mark

rx71king

iTrader: (6)

what part of new york do you live ...i like working on 1st gens...

74RX4

iTrader: (10)

Your symptoms suggest a vacuum leak. Check all the vacuum lines. Make sure none are disconnected or cracked.

roondawg

iTrader: (1)

After 32 years, a rebuild is a good idea. The problem is finding someone who will do it right. It takes time and talent.

t_g_farrell

iTrader: (1)

Sounds like a vacuum leak to me but if it sat for awhile and its all original then a
rebuild would be good to do on the carb. Rebuilding a carb is easy just tedious.

You have to make sure you have a nice clean clear area to dissemble and a good
diagram for reassembly. Taking pics can help and don't try to do much while its on
the car. Get it removed from the intake completely before taking bits and peices off.
Also throw some towels in the intake as soon as its off tos nothing falls down in it.

Kentetsu

The first thing I'd check is the fuel jets in the bottom of the float bowls. This is usually one of the first places that buildup will start messing with things...



.

boyee

iTrader: (3)

same thing happened to me. i am currently rebuilding it... taking forever. perhaps the pictures attached might tell why my car only liked to die at any rpm below 2500 (idle circuit) even with the slightest tap to the throttle. anything above 2500 was just normal revving behavior. driving with choke on felt fine too.

boyee

iTrader: (3)

so ive been posting in a few threads regarding nikki rebuilding but i found this one since it seems most relevant.

i finally got the time to put together my original 29 year old nikki. during the cleaning process i tried not to disturb any of the settings.

got it all situated in the engine bay and the engine turned over and fired up strong on the first try! i had leaps of joy... literally! it has been since the end of january since i last drove her.

now my issue is that its getting too much fuel. when i drive it around a plume of smoke comes out of the exhaust as well as a faint yet consistent smoke when idling. also when i step on the accelerator pedal while driving it hesitates and smooths back then hesitates again indicating to me that the engine is getting flooded. the engine eventually flooded to the point where i couldnt start it up anymore. i confirmed this by pulling the plugs. both of the trailing and leading were soaked and black. i deflooded it and the fuel that came out was very dirty like blackish brownish and i saw pieces of metal flakes! i should have purged the gas before i started the engine for the first time in months.

i am hoping its just the float needle/seat assembly is still breaking in. i followed mazda's carb manual and sterlings site instructions which were both awesome. i will continue to follow his troubleshooting guide now. it seems that my earlier hesitation issue is now remedied but now i have created another one.

boyee

iTrader: (3)

So I discovered I did not hook up a vacuum line to the rats nest. I saw the open port on the rats nest but did not notice I pushed the hose aside when I had to take off the carb again to find a washer for the OMP rod (I kid you not that rod is a bitch to install put back on).

Now it doesn't run rich anymore and no more white plumes of fuel smoke angering my neighbors. I believe that vacuum source could have been to vent the fuel bowls although I did have my FuelBowlVentSolenoid hooked up. But I have another problem... my car will not idle. Odd, because when it was running super rich, I could idle at 600 rpm. Perhaps I made something out of whack and created a new problem.. I hope it will run right for sevenstock though lol!

bahlorm

After you fixed the car running rich have you tried adjusting the carburetor? It may be out of adjustment since there was so much fuel going to it before.

LizardFC

iTrader: (1)

You probably just need to readjust the idle mixture via the idle mixture screw on the driver's side of the carb. If you still can't get it started, you can turn the idle speed screw IN until it will start and run on the primary circuit. I wouldn't turn it all the way in because it will cause a cold engine to rev up really high - not a good thing. Just turn it in a bit, try to start, and repeat until it fires up.

boyee

iTrader: (3)

Yea I messed with the idle mixture screw. I think that was a mistake because I messed with it before I discovered the vacuum hose was disconnected. But I do not believe that I messed with it too much that the engine will not idle. I tried turning the idle speed screw in a tad bit in but I do not want to screw that up, pun unintended.

I also noticed that fuel was leaking between the throttle body and the plate. Perhaps I will try tightening down the carb more down there. Otherwise I do have silicone and the right gasket from the rebuild kit. If this does not work, then I probably will examine the ACV and replace the hoses.

Thanks for the replies

superbee717

make sure engine is up to operating temperature before you set idle

boyee

iTrader: (3)

I always do. Thanks for the input!

I tightened down the four nuts that attach the carb to the base plate/spacer. This appears to have helped the engine idle and not die immediately. It will idle around 600 rpms fine. I noticed it is still leaking fuel though on the rear side of the carburetor under the throttle body between the spacer. Perhaps this is the reason why when I turn off the engine, it is almost impossible to restart it up. Also it smells as if something is burning and I can tell also by seeing smoke come from between the flanges of the precat pipe connecting to the Bonez cat I have. I think this smell occurs when the engine is running lean.

I talked to Glenn (DivinDriver) at JCCS this past weekend and he said he has a similar hot start problem due to a leak in the transition circuit causing fuel to leak out of the rear bowl and flood the engine IIRC. He recommended to check the gasket between the main body and the throttle plate. Can I leave the throttle plate in the car and just remove the main body and air horn? Or will that just be a PITA and I should remove the entire carb?

I confirm that I do have a very small vacuum leak around the rear side of the carb from spraying carb cleaner and hearing a difference in the sound of the idle when I spray (idle drops a bit but very subtly). I believe this is causing the remainder of my idle/hot start/lean issue.

The original hesitation issue is apparently resolved now from the rebuild of the carb. The huge smoke screen of fuel seems to also be resolved from hooking up a vacuum line I missed.

Man, JCCS really motivated me to get my car running right for Sevenstock on Oct 29 at the Fairplex in Pomona! Thank God I have this extra time to get her running right.

DivinDriver

iTrader: (15)

Was good talking to you, Boyee.

It's not the transition circuit that is my current suspect, but the enrichment circuit: It's one of the few fuel-bearing paths that actually penetrate the gasket between the throttle body and main body. I'm not 100% certain that the issues lies there, it's just my current hypothesis, based on finding gas where gas shouldn't normally be.

As far as disassembling the carb while on the car goes, it can be done (I do it when working on floats) but in my book it's safer to remove the entire carb to the workbench, as if you drop any small bits down the bore and they make it past the butterflies (perhaps because you bumped the throttle), you're looking at possibly having to tear your engine down to get them back.

It's unfortunate that removing/installing the Nikki isn't easier; adds a lot of time to troubleshooting otherwise simple issues. but it is what it is.

boyee

iTrader: (3)

Always a pleasure chatting with you too Glenn (I hope I spelled your name right with two n's).

Anyways I finally took off my carb again. It literally took 5 minutes to get off the engine as always when you get the joy of having to do something over again.

I saw fuel on the threads and the bottom of the long bolt that goes through the center of the carb assembly. Also I ssaw fuel on the top and bottom gaskets on the spacer as well as on the gasket between the main body and the throttle body. I also think I did not tighten the access hole bolt tight enough for the rear fuel bowl because I saw some fuel in that region.

Well I suppose I will re-tighten everything and replace the gaskets on the spacer and between the throttle body and main body and see if I get any more fuel and vacuum leaks.

boyee

iTrader: (3)

A small update:

I discovered my fuel leaking through the access holes for the fuel jets on both sides. Tightened those four screws down and installed a new gasket between the main body and throttle body. I got lazy and decided not to replace the gaskets between the spacer because I did nit want to scrape the old silicone glue off too and then re-apply the silicone make-a-gasket and wait for it to set. I felt the gaskets though and they feel solid hard, not rubbery like I have heard.

My results, my car still has a vacuum leak because it will not idle at all. It only runs with the choke on. I sprayed some carb cleaner around the base and noticed the idle went up slightly. I also took off the spark plugs and installed brand new NGK BR8EQ14. This helped with startup but still had the same symptoms of not idling. I have not noticed any more fuel leaking down the sides onto the spacer anymore though!

Guess my laziness kicked my *** because I will attempt to take off the carb again and replace the gaskets for the spacer included in the kit with silicone.

boyee

iTrader: (3)

I took off my carb once again (seems like I'm getting pretty good at this)! My problem is that the engine will not idle still. Any RPM above 1500 and the engine performs splendid!

I also removed the spacer in between the carb and intake manifold. I plan to remove the gaskets and put the new ones that came with my rebuild kit along with some silicone gasket sealant between the spacer and gaskets. I am hoping that my vacuum leak lies within the spacer and corresponding gaskets.

Anybody have any tips to scrape off 29+ year old hardened gasket/sealant?

I noticed, again, that the long 14mm bolt in the center of the carb had fuel on the bottom of it as well as on the threads when there should not be, as I am told. I also noticed some fuel seeping through the fresh gasket I installed last week between the main body and throttle body. Hopefully by separating them again, wiping the gas, let the gasket dry, and re-install with more force on the four bolts to better secure the two bodies will cure that slow leak. Although, I worry that if I put too much force on those 10mm bolts, I will strip the threads, and then securing the bodies together tightly will be impossible. Is that possible?

I swear I feel I am very close to getting everything running right so I can take my car down to Sevenstock. Thanks for reading and for your replies.

boyee

iTrader: (3)

Before I get to how my re-re-re-installation of the carb went... I should mention that before I took it off to redo the spacer, I did not connect the accelerator pump linkage as well as the secondary throttle diaphragm linkage. I also did not have the teeter totter hooked up in the right location.

Ok so the answer to scraping off old and hard gasket+sealant is a very sharp blade. My results also included beat and cut up fingers. After I scraped off the old gaskets, I bought Type 2 gasket sealant. It was this black goopy substance that I spread carefully with the tip of an X-Acto blade. Then I placed the two gaskets supplied in the rebuild kit. I also blew out the vacuum lines with carb cleaner to clean any junk inside.

As for the seeping leak between the throttle body and main body, I tightened the four 10mm bolts some more as they were loose. So, to answer my other question, it is not possible to overtightened and strip the threads of the hole if you know how much to tighten the bolts. Otherwise I suppose it could be possible to damage the threads by overtightening.

So the end result of regasketing and resealing the spacer part was a complete success!!! NO more idling issue as it idles and purrs ever so smoothly!

But unfortunately, I seem to have encountered another problem... any reply to help with my issues is much appreciated.

1. I have a horrible stumble again from idle to about 3000 rpm. When I give it a little gas, the engine would appear to cut out and drop rpms and then I would have to keep feathering the throttle until it climbed to 3000 rpm or higher and the hesitations will go away. I fear this may be another vacuum leak? Perhaps my shutter valve needs replacing? I will also check my ignition system again. I will also put the gasket sealant on the high altitude compensator gasket since the rebuild kit did not come with this gasket and the original gasket is hard and dry like my old spacer gaskets.

2. My choke will not stay out by itself. I see the linkage connected properly and is moving the plate to be closed when I pull on the choke lever. I also know the check relay is working because I can hear it click when I take out and put in the 15amp Engine fuse with the key in the on position. The dummy lights also are on when the fuse is in and off when the fuse is out.

3. Another thing with my choke is that even when I manually hold the choke lever out, I do not notice any change in rpm from idle. It is like my choke system is not working at all! But it is interesting that the plate on the top of the carb moves still.

Well after connecting the AP bracket linkage, secondary throttle diaphragm linkage, teeter totter, regasketing and resealing the gaskets in the spacer, and adjusting the idle speed and mixture, all AFTER I rebuilt my carb for the first time ever, I am finally about to drive her around even though she is still running with some power and choke issues as described above.

I feel even closer to getting her to run super! And Sevenstock is getting closer as well...

Oneiros

Check that the accelerator pump is working correctly. Look down the barrels while opening the throttle by hand, you should see a little fuel come out as soon as the throttle starts to open. It sounds like you either need to fix up the adjustment nut, or the AP circuit may not be working properly at all due to lost check ***** etc.

The choke system includes a "fast idle" arm, which pulls the throttle open when the choke cable is pulled out far enough. Do some searching and you will find pics, or check the carby manual. You probably need to adjust the fast idle arm so it pulls the throttle open earlier when the choke cable is pulled.

boyee

iTrader: (3)

Thank you for your reply Oneiros.

Hesitation issues:
Today I tinkered with her for a bit. Turns out, I missed connecting a vacuum hose unless it popped out by itself which seems a little unlikely. That helped my idling issue a bit, but I still have a slight stumble from idle to 3 grand. If I am not careful with the throttle, the engine may still stall. Lesson learned again and again that it is crucial to be very thorough when working with the carb and emission system! But she is a lot more driveable now especially starting from a stop. I will double check the accelerator pump, but my gut feeling is telling me I still have a vacuum leak.

More sources indicating a vacuum problem other than the idle to 3 grand issue is that sometimes there is air coming out of my ACV constantly and it makes a honking noise when I keep increasing the RPMs. Sometimes this happens, other times it doesn't. In both situations, I still experience the stumbling. Also, if the engine is at or under 3000 RPM, and I am driving, if I let off the throttle completely and then put my foot back on it again, I get a very noticeable hesitation or cough of power. Sometimes it is more smoother than other times but regardless it happens consistently. Also, I connected my teeter-totter to the right position and definitely feel a lot more power, but I don't feel my secondaries coming on as strong as before. So I am not sure they are even opening, thus adding more to my gut feeling that I have a vacuum leak.

I found out why my choke was not working:
One of my No.1 temperature switch wire was broken. So I cut the other one and jumped them together. This allowed my choke to stay on all the time. I noticed that after the car has warmed up, I need to disconnect the switch/plug because that causes an even worse hesitation that I cannot even bring the engine past 1500 RPM. After disconnecting the plug, the engine is back to its current state with the hesitations happening until 3000 RPM. Also I tightened my choke cable which helped the my-choke-does-not-do-anything-even-when-manually-pulling-out-the-rod problem.

I think I might bite the bullet and hand her over to Paul at Rotorsport to have a look because I really miss driving her and only have a few hours to work on her during the weekends. I also really want to drive her to Los Angeles for her third Sevenstock in a row. But I gotta say, driving her even if I had to limp her home because of the iffy hesitation/might-stall issue, felt great.

Again, all help is much appreciated!

boyee

iTrader: (3)

Well a brief update:

Confirmed that my leak is not coming from the shutter valve as it is operational as well as there is no air being sucked in from the hole in the air canister.
Also for some reason, my ACV is working properly and the air honking noise has decreased in sound such that it sounds like how it used to be IIRC.
I also applied gasket sealant on the High Altitude Compensator just to make sure I was not getting a leak there since the carb rebuild kit does not come with this gasket.
Turns out I got nowhere to resolving my slight hesitation but at least I knocked off a few items of what wasn't causing my issue.

I found a way to make the hesitation issue go away 99%. Keep the jumped plug from the broken No.1 temperature switch plugged in and pull out the choke rod such that it is idling around 900 to 1000 rpm which is just slightly higher than idle. the choke rod will always be in this position and so will the performance of the engine.

Regardless, I have ran out of time to work on her. Although I feel I got really close to getting her fully operation (I have not driven her regularly since January ) I will take it to Rotorsport and have Paul take a look. Hopefully I do not have to cough up a lot of dough as hopefully the remainder of my issues are minimal at this point. Plus, aside from the hesitation issue, I need my temperature switch fixed, my differential and transmission gear oils changed (I have bought the Redline fluids years ago and they have just been sitting on the shelf in my garage).

Thanks for reading!

boyee

iTrader: (3)

Just spoke with Paul at Rotorsport and he said he found a couple things that weren't working: float bowl vent solenoid, accelerator pump circuit, and the "modified" spacer I made as a patch for my vacuum leaks.

So the accelerator pump diaphragm that came in the GP Sorensen rebuild kit was replaced with a genuine Mazda part. My spacer and FBVS was replaced by used working units Paul had with his spare parts. My timing, fuel mixture, and speed (at idle I believe) were adjusted. My temperature switch is on its way from Los Angeles (8 left in N.A.). I dropped her off before they closed Monday, Paul finished yesterday, and I'll be picking her up tomorrow. Great work and fast turn around keeps me coming back! I can't wait to drive her from NorCal to Sevenstock!

boyee

iTrader: (3)

Wow is all I can say about how she feels after picking her up last night engine performance-wise now. I could not have done it without everyone's contributions and support and of course Paul, Kevin, Judy, and everyone else at Rotorsport! They did not only manage to fix my issues but made her unleash a lot more power than I remember! See everyone at Sevenstock!