1979 Barn Find - Unable to idle
 

Hey everyone,




I'll give a little back story, as it may be helpful in diagnosing this.


I was lucky enough to find a near-mint 79 SA sitting in an old gentleman's barn. 50k on the odo, 40 on the engine. Hasn't driven since '96 and hasn't been started in 2 years. I currently have an RX8, and have done pretty extensive work on it, be it reliability or other things, and figured I'd give restoring this beauty a go.


After getting it home I pulled the plugs and gave it some idemitsu premix, turned it over and let it sat overnight.

Next day I went to change all the filters (oil, air, fuel), and while changing the fuel filter I found the fuel pump power cable sheared in half, as if it was riding on the small opening in the frame and cut itself. Was told by the seller that the last time he started it 2 years ago he backed it out of the barn and it randomly died, and had to push it back it. I'm assuming this was the cause of that problem. Some soldering later I had it up going and letting the pump do the work for me in draining the fuel tank, though after getting it started with the ignition I just let it gravity drain. Filled it up with 87 octane, as I read that the old 12as were designed around low octane, high quality gas. Wouldn't cut it in my Renesis. :)

All the fluids were brand new, changed right before it went into its final storage. Oil, coolant, brake fluid, etc, completely clean and no need to change. Clutch fluid was the only thing gross, and in bleeding it I found it leaking from the seal inside the cabin near the pedal, so I'm going to replace both master and slave sometime soon. Clutch itself won't disengage, so I'll just assume this is the problem for that.


Anyway, put the old plugs back in and fired her up. Stumbled hard but after awhile I got her up and running strong, though with my foot on the pedal to prevent it from dieing.



Has been started multiple times so far, and while she runs fine when using the choke or babysitting the accelerator, she will die the second or two after either of those go away. Completely unable to idle without assistance. Has been ran up to 7k to be sure all the old fuel is out of the system, or at least I think it is.


I will be replacing the old spark plugs tomorrow, as there is certainly a small misfire under load, but I do not believe that alone would cause it unable to idle.


My question is where should I start with diagnosing this problem - A/F mixture? Idle adjustment? Floats? I have searched plenty about adjusting the above, but I want to know if the carb is the cause of this problem, or if there's some wizardy that I'm unaware of that would be the root of my issue.


Thanks in advance,
alphawolff




TL;DR: 50k mile 79 SA hasn't been driven for 20 years, sat for 2; won't idle without choke or foot on accelerator.

When you rebuild the carb, and you will, leave the stock needles and seats alone! Please leave them alone.

You have no idea how many carbs were essentially ruined by someone who wanted to get their carb back up and running, but ended up causing an unsolvable flooding problem using the garbage quality seats in all rebuild kits.

Do yourself a favor and avoid changing the needles, seats, and float levels. These must remain unchanged or, you guessed it, flood city!

Forget what the instructions that come with the rebuild kit say about adjusting floats. Forget what the FSM (factory service manual) says about adjusting floats.

"Leave yer damn floats alone!"
-- Sterling

The baseplate gasket in these kits is very thin. It is best to use it as a template on some thick paper. I'm talking about the gasket that goes between the main body and cast iron baseplate.

Speaking of baseplate, do not use any of the gaskets that look like they sit between the carb;s baseplate and the phenolic spacer. Most kits come with four. None are useable as the original gaskets are bonded to the spacer and can not or should not ever be removed. The originals don't leak. That should be good enough.

The only few parts from a typical rebuild kit that should be used are the air horn gasket (the 79-80 style in your case), the site glass window rubber seals and gaskets, and lastly the accel pump diaphram. A new one of those always works better than a tough old hard one with the consistency of a leather belt.

If you take the air bleeds out, please try to get them back in their original holes. Same goes for fuel jets.

The new copper crush washers that come in the kit can be used on the jet plug bolts, but the stamping process hardens them so heat them just enough so they glow, then let air cool. This process is called annealing and softens copper so it can be used again and again. But because you have no need to tune your carb, one heat up and one install cycle is all you need.

Hmm, anything else? Oh you might not need to loosen or mess with the banjo bolts up on the fuel rail. There is just a strainer in there that is probably ok. Only loosen them to get at the strainers if you suspect something is clogging them. Otherwise you create far more work for yourself for little to no gain, and the odds of ruining the carb go way up. I've seen lots of ruined threads in carb tops due to this misguided effort.

If you follow my advice, your rebuilt Nikki will work perfectly the first time you fill it with gas and turn the key.

Thank you very much for that advice. I'm assuming the inability to idle is indeed directly related to the old carb.

I'll look into kits and get to rebuilding it, I'll be sure to double check this thread again when I get down to it.


Believe it or not, the previous owner had an actual paper copy of the 1980 haynes manual and the 1979 FSM, which both came with the car. Lucky!

Jeff is giving you some good advise. Also when you pull the top off the carb be careful of the
posts that are the float hinge, they like to fall out. If you remove some of the jets to get better
cleaning make a diagram with the numbers from the jets so you get them back in right. The kit will
come with one but its very hard to read and sometimes wrong based on the carb you are playing
with. The best thing I've used to get the carb clean is soaking it in some carb cleaner and then
liberally dousing it with mineral spirits to get the varnish off better. Modern carb cleaning solutions
just don't cut it like they used to. As Jeff said you probably don't have to adjust anything at all.
Leave the float height alone and leave the idle and air mixture screws alone. Just get it all real
clean and put it back together. I would also take this time to replace all the rubber gas line as it
may be contributing paticulates in the fuel which will end up on the carb screens.

Oh, and we demand pics as payment. Its easy to post them here or link em.

Good luck.

Hold the phone boys! If the car runs fine and makes power, there’s a reasonable chance you have vacuum leaks instead of a carb problem. Especially since those 14 miles of vacuum hose are now 36 years old and brittle as great aunt Mary's bones!
Start by replacing the vacuum hoses or at t very least, looking for cracked ones! It'll be a lot less headache than rebuilding your carb!
Don't touch the carb at all until you rule out vacuum leaks, or you'll make more headached!

You wouldn't believe how many leaf-covered, rust destroyed cars we've hauled out of the Bush that will idle just fine on 50 years old carbs.

I'll look for vacuum leaks, though I though they usually -raised- the idle to stupidly high amounts, rather then causing it to randomly die.

Had some of the pictures from when I just started working on it. Here ya'll go, please 'scuse the messy work space, but it's all I have for the moment.

- Album on Imgur

Also here's the fuel pump as I found it. It appears to of been repaired once already. I just cut the repair out as well and spiced two new wires in. Works great now, but it's noisy as hell. Not too sure how long it'll last.


Imgur

Vacuum leaks do usually raise the idle. But a correct carb rebuild can help in lots of ways. Plus it gives you an excuse to remove stuff and notice broken little rubber vacuum tubes and other problems you wouldn't have seen otherwise.

And before you get any ideas about modding your carb, please do about a hundred hours of reading up on how to do it well. :) I've recently posted a whole lot on the subject so any of my posts are good ones to search for.

Also be sure to check out posts for how to do ignition upgrades such as DLIDFIS. Find the pros and cons. I recommend an ignition upgrade, especially on SA cars (79-80) because they are really improved unless you still have to deal with emissions where a rich running condition is required for the thermal reactor to function as intended. That's why I like 81-85 cars better because they are better when it comes to ignition. ;)

I'll be replacing the rotor, cap, and wires in the next couple of days.


Is there a current DIY on removing the rats nest? The only one I found has been deleted, which is from the FAQ. I have the diagrams, but am not sure what is fine and what's not fine to remove. Going to be replacing all the vacuum lines while I'm at it.

I'll certainly upgrade to an electronic system once I've gotten her road worthy

Don't do it. Get it running correctly in it's current configuration before removing the rat nest. Don't want to introduce unknowns.

My 84 died at idle because the diaphragm in the shutter valve was shot and leaking. Ran fine out of idle.

Its not part of the carb, but if you have it on yours, its located under the carb. During a fast de-acceleration it dumps fresh air in from the air cleaner to suppress backfire.

(I think that's correct. I replaced the valve and it no longer died at idle.)

Speaking of backfire, it's currently backfiring like -mad- after giving it any substainal throttle.


I'm assuming if it's busted and leaking air, it's also not supressing backfire as it's supposed to. Though I'm not too sure if 79's even have it, according to https://www.rx7club.com/1st-generati...-valve-683769/

I'll give it a good lookover tomorrow, thanks a bunch for the picture. Currently am going down the driveability list found here: http://www.mazspeed.com/diagnosingdr...typroblems.htm

It mentions the shutter valve too, so I'm guessing it's a common issue, but again mentions 81-85 only

I think we're all waiting on pictures at this point...:bigthumb:

Linked an imgur album quite a few posts up, but will upload them on-site as well. These were taken first day I got her home and had just finished oiling up the rotors.

Some updates - after confirming I had no vacuum leaks I decided to go ahead and use the FSM to adjust the idle and fuel mixture. As a result I was able get it t idle by itself for around 20-50 seconds, with a tap of gas when it's about to die will give it another 10-20 seconds of life before dieing again. Starting to believe it just needs a carb rebuild.

Also took it for its first drive today - tach is super spotty, just jumps everywhere; speedo doesn't work. I checked both endes for a connection and cleaner it - no dice. Still am unable to get the headlight to flip up correct, sometimes only one will flip up. Starting to think the fusible link has a spotty connection.


One thing slightly fixed and five more problems pop up ;_;

Update! I'm unable to edit my above posts, so I apologize for the triple post.


Replaced the rotor cap and wires today, and spent the 5$ on carb cleaner - the result: idles like a beauty!

Thanks for the help here guys, now I'm on to other issues. Jumpy Tach, non-working speedo, and headlight flipping issues.

Jumpy tach problem
 

This problem is caused by the bearings under the points baseplate in the dizzy that have worn a groove in it. Either replace the points baseplate or get a new dizzy from an 81 to 85 FB.

The 79 does not have a shutter valve.

The jumpy tach can also be caused by a bad connection a the spade lug that connects the tach to the leading (yes, leading - on an SA) coil.
Best way to check where this problem comes from is to buy/borrow a test tach and clip it to the battery and the coil stud. if the in-dash tach jumps but the test tach doesn't, that tells you to look from the tach connection forward. If both jump, then the problem is between the dizzy and the coil.
A car with only 50k miles on the clock should not have significant wear on the points-plate bearings.

Great information here in the newbie section already, thanks.