Converting to manual choke?

[m87]

I’ve got a carburettor 2Y that seems to be running rich. Idles fine, but falters when given a small amount of throttle, especially under load (eg cruising in third gear). Spits black gunk out the exhaust when revved hard on first start, and idles rough until revved to clear (even when warm?).

Any ideas how I can convert the vacuum choke to cable, or at the least take the choke outta the equation to test the theory?

Edit: revs fine at higher rpm with ok power (for a clapped out 1.8 petrol), it’s just faltering/gutless when the throttles open at low rpm.

[m87]

Update, blasted it with a bunch of carb cleaner, which seems to have helped. Weird thing was that the butterfly on the upper right was open, then stopped shut on start. Is it supposed to do that? Sticky?

also looked in the little window thing... looks either full or empty... I’d guess empty? It’s the same regardless of wether it’s off, idle, or running as far as I can see. Is that normal?

Bunch of videos and photos here https://imgur.com/a/SBcyw

can anyone tell me which hose is the choke? I.e. which hose to pinch off to disable the choke?

[boogieman]

carburetors? yuck...our vans are civilized efi so most are not going to be familar with your setup...from the looks of that carb, a good cleaning/rebuild would be the 1st thing i'd do..a manual choke looks like it would be pretty straight forward...the choke valve should not slam shut, possibly some linkage or the bimetal coil in the circular device that the shaft goes into is faulty...you loosen the screws around the perimeter to adjust that and can just crank the butterfly open to test that is the problem...

[m87]

Thanks Boogieman, I'll give that a shot soon. Yeah unfortunately for Australia, we got the garbage version with carb, even though EFI was available at the time (for years), and obviously shipping everywhere else in the world! Who knows why :?:

Update from today was that the carb cleaner improvement may have been my imagination - still stutters and power dies when a whisker of throttle is applied in 3rd at 35-40km/h...

[boogieman]

so it runs fine up til 3rd gear? i wonder if its a fuel delivery issue, either fuel pump or needle seat/float maybe

[m87]

Could be? It’s not just 3rd gear, it’s the combination of light loading (driving on flat road) at a specific speed for each gear (I.e. rpm) and a light prod of the throttle, like you would to maintain speed. Accelerate past that, and she will get going properly.

Carbies, the mechanical world’s very own version of wifi troubleshooting / voodoo spellcasting :dizzy:

[Burntboot]

Carb's work perfectly fine, like all things, they have gained a bad reputation from people who don't know how to use them or care to learn.
That carb is filthy but you shouldn't tear into it till you know whats wrong.

One word on starting a carb'd engine, blip the throttle a couple of times
This is a mechanical system, the engine was hot when you parked and the choke was fully open.
When you blip the throttle it unloads the linkage and allows all the springs to reset to cold status (choke shut, fast idle engaged)
When you start the engine, the first bit of vacuum hits the "unloader" dashpot and cracks the choke plate open ~1/8in so that the engine doesn't flood.
Then the engine fires and goes to fast idle (~2200'ish rpm) now the choke heater starts to warm up and the spring expands, choke plate rotates open.
The rpm will only drop if the throttle is blipped again, due to spring tension on the linkage.
RPM should drop back to normal once the choke plate is fully open.

First you need to free up the choke (not just the dirty little round thingy) its the shaft it bolts to and everything along that shaft that must be freed.
Good penetrant with straw applicator, get it into where the shaft rides in the housing. there will also be several devices attached to that shaft.
It will be linked to the throttle shaft and the high speed cam before hooking up with the actuator.
Blast everything with quality penetrant, no oil or grease, slightly open the throttle and hold it there while you articulate the choke plate and everything attached to it until it all moves easily without any sign of binding and that link that attaches to the fast idle cam should be able to move independently from the choke shaft once unloaded.
Do not put oil or grease on linkages, it attracts dirt and encourages binding/seizing.

The bimetal spring is only part of the choke story.
There will likely be an electrical heater and/or engine coolant circulated thru.
Resist the urge to adjust anything at this point.

That window you found is the sight glass, clean it and use a flashlight to ascertain your fuel level within the carb.
It should be mid-way between the upper and lower protrusions and not beyond either.
If the level is too low, it will run like crap (if at all) be low on power and run hot (lean)
If the level is too high, it will run like crap (if at all) blow black smoke and run cool (rich)

Once you have freed all the linkages, you need to test and observe.
Cold engine required.

Blip the throttle a couple of times to set the choke, fast idle and give the engine a shot of fuel to aid in start up.
Once running, watch all events unfold as described above and once its up to operating temperature, look for vacuum leaks.
Place your hand over the carb intake to close off the air supply to the engine, you can attenuate the amount of air entering by spreading you fingers.
As you start to restrict air supply the engine should increase rpm a little, like 500 rpm max, anything more would indicate a vacuum leak.
Continue to restrict the air and the engine should die, if its still running, it has a vacuum leak.
Leaks can occur at body gaskets, o-rings, base plate gaskets, vacuum diaphragms ....
Needle nose pliers are handy for pinching off hoses, propane is good for checking gaskets.

The 2nd test for any diaphragm is to pull the far end of the rubber hose off, compress the valve and plug the hose with tongue (or suck it closed) it should hold in the closed position until you release your tongue. You shouldn't taste raw fuel when sucking on a vacuum line, faint scent is one thing but nothing more)
And don't forget to check the the dashpot to advance the timing on the distributor (if so equipped)

Report your findings and we will take it from there.
Hopefully its just a bunged up linkage.

Cheers
BB

[Burntboot]

And please don't get into the bimetal actuator at this point, there is good reason GM starting putting them on with rivets, its not so much that they are adjustable as they are set at the factory, once set further adjustment shouldn't be required.
Springs don't usually only break under normal operation, though I have seen several destroyed by well meaning and ill-informed owners.

Address the other issues first, if you need to go deep its not a problem but there is a proper order to things and failure to follow procedure only makes diagnosis harder.
BB

[nikifix]

I dream of having carbs on my vans.........no more computer ,nasty in the tank fuel pump, fuel injectors leaking ..I would have..carb....points condenser...yeah stepping back to the caveman days....but hey if the beast breaks down you have a chance of fixing it....on the side of the road.

[m87]

LEGENDS.

I'll get going on this this weekend! :dance2:

[m87]

Update is that I spent the weekend setting up cabinets, but next weekend is a long weekend!

It did make 250km without a hitch. Not super strong uphill, and still stumbled at that particular throttle position, but good enough to get the job done.

Also now sporting a truck air horn :LOL2:

[m87]

Decided to confirm fuel consumption suspicions before I went tearing anything apart. I can live a the faltering throttle, but not bad fuel consumption!

Turns out it's burning 14.84L/100km... 15.87mpg on a 1812cc petrol, where most of the actual consumption was highway action at 100km/h. :nono: no es bueno.

Oil seems thin, but it takes thin oil anyway, and there's not really a fuel smell from the old stuff or the dipstick post-new-rear-main-seal. The 2 black catchcans behind the front left wheel (front right for you guys?) smell a bit fuelly though. Otherwise it still barfs black schmoo on cold start when revved, so is probably just running very very rich?

Hmm. Looks like the carb will be dismantled after all.

[m87]

Made some maybe progress today thanks to your suggestions - stepped through it all, cleaned the choke’s spindle thing best I could, and the throttle linkages with carb cleaner.

Starts first go after 5 pumps of the pedal, which is nice, but quickly dies if not given any throttle blips. Observed the choke on cold start, seems to slowly open more and more as the engine warms up (not on/off like I’d assumed. Couple of mins running and it stayed open nicely, both when killed and running. It flickers when revs are dropped, but I’m assuming that’s the throttle linkage?

Was looking/filming down the barrel while revving, and the one to the right doesn’t seem to actually do anything. The one on the left had fuel coming from down low, in the wall of the barrel, and from the brass thing in the circle. The right hand side? Nada. Normal? Dunno. https://youtu.be/nDWdrIOow_8

i cleaned off the float window, and it’s dry all the time in there, from what I can see. It’s not full, I’d expect more color from the fuel, and for it to distort shadows cast on the float hinge or whatever that thing is in there. No distortion and no color. https://youtu.be/roVSrAeSiTw

When I blocked off the air, it seemed pretty keen to die once my hand was close to flat, and quickly died when my palm rested around the whole rim of the intake, and that’s with loose fingers. It recovered fine from dying to idle with my hand over it. No upwards change in RPM either. https://youtu.be/5Rs3J74m8ZM

Have attached video for each thing - let me know what y’all think?

[m87]

Oh also I got a textbook out and did a test for accelerator pump, couldn’t really tell if it was jetting fuel in (while off) through the full range of depressing the go pedal... couldn’t spot a “strong stream” anywhere, but whisps of atomised fuel could be seen floating up and settling in the throat when I tried it on a warm, off engine. Image of book/accelerator pump test here: https://imgur.com/a/mTl1C

[Burntboot]

Haven't had a chance to look at vids yet but heres a few thoughts in the meantime.

2 bbl carb - most of the time it runs on 1bbl only, the 2nd Barrel is only going to come online with full throttle/hard acceleration.
So I would think your good there.

Accelerator pump - You should be able to see a squirt of fuel, if the pump is failing (common problem) it will create a dead spot when trying to accelerate
(smoking gun found?)
The fact that it takes 5 pumps for a clean start is also indicative of a bad accelerator pump.

The choke should open slowly, idle will only drop when you blip the throttle to reset the linkage.

Fuel is very hard to see through the sight glass, if there was no fuel visible, the vehicle would not run and if it did, would run lean not rich.
I would suspect that the float level is too high, most likely due to a porous float and what your actually seeing is the float bowl overfull.
This too would explain the awful fuel mileage and the black smoke.
Understand that running rich will thin the oil and can cause internal engine damage, best to sort it out sooner than later.

So we know the Accelerator pump is toast and you've got to get inside to action it, I would bite the bullet and get a carb rebuild kit and a new float.

OEM stuff will likely not come as a kit, all pieces usually individual, A/M stuff will be a kit and is usually sufficient, a kit should come come with a new needle/seat and accelerator pump, but not the float. (A/M kits usually come with instructions, which can be handy sometimes)

You should soak the disassembled hard parts overnight in cleaner, then blow everything out with compressed air (many small internal passages)
Have a clean work area and be careful pulling it apart, sometimes theres springs or balls that can fall out if one is not careful.
Its also a good idea to know just where those loose parts actually live, makes reassembly MUCH easier.
Unless that carb was used on many models, you may have to go dealer to get the float (and possibly all the required bits)

Rebuilt units are sometimes available, but I have not had good luck on that road and have learned (the hard way) to action things myself.
BB

[Burntboot]

Oh, and that comment about sealed mixture screws in the last link, is true but you still have to pull the mixture screw to do a proper cleaning.

The cap is thin metal and the mixture screw is right below it, you can use a drill but have to be VERY careful not to go too deep, once the cap is punctured you can use a tool to pry the cap out, sometimes just tapping to one side with a punch will be enough to cock the plug enough to get some purchase on it.
The kit will probably come with a new cap but I never install them.
A preset mixture screw is great when things are new but as the carb wears, being able to tweak the mixture screw, pays many rewards.

I did check the vids, the first one shows a lot of fuel in the top of the carb (outboard of the main venturi) and while I am not familiar with that particular carb I would say that is further indication that the float level is incorrect.

BB

The float bowl is vented, usually into the portion of the carb where yours shows liquid fuel (in the vid), so it would appear that the fuel level is so high that its pushing fuel up the vent tube and its running back down into the carb and the cause of it running rich.

[Burntboot]

One more thing, when your ordering your parts, make sure to get a new base plate gasket (carb-manifold)as it doesn't usually come in a kit.

[m87]

Legend BB, thanks a million for the help. I'll post you some beer if this thing makes its renovation deadline (fitting out for a trip at end of the month).


Am tossing up between getting this carb (https://www.ebay.com.au/itm/CARBURETTOR-CARBY-SUIT-TOYOTA-HIACE-2Y-3Y-4Y-YH53-YH63-YH73-1-8L-2-0L-AISAN/192325657855?hash=item2cc780a4ff:g:6sMAAOSwKZ5Z1iV s) and this kit (https://www.ebay.com.au/itm/MAJOR-CARBURETTOR-REPAIR-KIT-SUIT-TOYOTA-LITE-ACE-YM21-YM30-YM35-2YC-1-8L-84-92/192325491639?_trkparms=aid%3D222007%26algo%3DSIM.M BE%26ao%3D2%26asc%3D20140106155344%26meid%3D244fb6 8ec962425ba7892261c1f1ce3d%26pid%3D100005%26rk%3D2 %26rkt%3D2%26sd%3D151918051199&_trksid=p2047675.c100005.m1851). It's $150 between them, but the thing I'm liking about the whole carb is that there's less likely that I'll roflroflroflrofl something up, and have to tow. Even if the new carb is DOA, I'll have the old one to put back on and limp into the shop...

My engine number is 2y0430627 - think that carb is the right one? Looks similar!?

Scratch that... have ordered the kit so a mate and I can learn a bit, and will hope for the best! :dance2:

Anyone know what kind of fuel filter I should grab while I'm at it?

[JDM VANMAN]

Anyone know what kind of fuel filter I should grab while I'm at it?[/QUOTE]


Here’s your fuel filer part number-

Good luck

JDM

[m87]

Thanks JDM, I’ll check the one I found on fleabay matches the one I have somewhere in there, now I know what to look for!

[m87]

Well well. *sigh*

Did a bunch of internet learning (youtube videos, articles and gifs) to upskill the theory in all things carb. Then pulled the carburettor, tore into it, and cleaned A LOT of roflroflroflrofl out of the accelerator pump, and replaced as many things as I could recognise from the kit, with only a few small bits left unused. Learned that kerosene is a waste of time as far as soaking is concerned. Gets varnish gone, but leaves stains and baked on crud, and does nothing against old gaskets. Enter elbow grease.

Found fuel behind the accelerator pump and the smaller side of the choke pulloff. No es bueno.

Unfortunately, the kit only came with the main side of the choke pulloff, the smaller side with the pin/bellows thing was also dickered in the process of disassembly, so I blocked vac lines to the choke pulloff and the other side, and put silicon around the outside to ensure it holds vacuum. That said, the bimetal spring does a good job still and she warms in a minute or two, running with choke all the way off.

Turns out the full-looking sight window was actually empty all along, but at least with a new float (tweaked to hilux level from youtube because my kit didn't come with instructions :pissed:) there's fuel halfway up the window when she's idling! So I think what was happening (hopefully thats a definite WAS), is that there were a couple of leaky bellows/seals that meant the vac system was sucking fuel through all the wrong places and dumping it into the intake and the charcoal canisters. So it was running lean as hell in the bowl, but sneaking a heap of fuel from elsewhere. Feck!

Put 135km on it last night, seems much torquier at high RPM, probably because the 2nd throttle plate now opens (sometimes? is sticky as hell still). It was SUPER sticky in there, and I'm not sure the large bellows thing that is supposed to move the cam to allow it to open, was doing its job. It still won't accelerate when in 5th gear up a slight (I mean slight) incline, but it does hold speed much better, with less accelerator required on flat. I did manage to notch the throttle cable putting it back in or jam up the throttle plate because now its sticky and won't drop back to idle after having the pedal down from time to time. I did lube the cable but still sticks a bit, which is SUPER GREAT, just what I need.

It used about a 6th of a tank (7L?) driving mostly flat highway speed, over 81km. My back of napkin puts it at 8.6L/100km which is roflroflroflrofling great compared to 15+. Unfortunately, still stutters on light throttle. Did notice the little cam that actuates the pump is a bit worn, could that have anything to do with it? Throttle angle too high, without activating the pump?

More pictures and questions in the photos here: https://imgur.com/a/SxFOj

TL;DR: Rebuilt carburettor. Blocked choke pulloff. Maybe solved fuel consumption. Still stutters on low throttle. Still gutless in 5th gear up *any* hill. Throttle now sticky. Progress.

[Burntboot]

Well, see, that wasn't so hard :)

So, 1st things 1st.
I go out of my way to avoid "modifications" especially when dealing with drivability issues.
That said, it would appear that your pull-off mod is at least not causing a vacuum leak but here is no way of knowing if it is impacting any of the other issues you are experiencing. Personally I would be looking for a replacement diaphragm and settings things right. Toyota doesn't generally install unless redundant systems.
Not saying it will cure all your woe's but there

That big black hose should be the canister purge pipe.
Fumes are collected and stored in the canister and when appropriate, the carb will suck the excess vapours into the carb to be burnt off. Canisters should never be exposed to raw fuel, vapour only, a (raw-fuel) saturated canister will cause all sorts of drivability issues.
Theoretically, one is supposed to replace any contaminated canister, but carbed vehicles are much less sensitive and should be just fine once dried out.

Then there's the orange silt in the bottom of the float bowl.
That is RUST from the fuel tank.
Tim had a similar issue on one of his vehicles that he actioned, IIRC, with an extra filter as FI is far more sensitive to contamination issues than carb's.
That said it will still cause havoc and needs to be addressed.
Adding a extra filter will keep the orange death out of the carb but won't solve the issue.

The easiest fix is of course replacing the tank, that is also the most costly and quickest fix.
2nd option would be to remove the rust with electrolysis, the great internet Gods Google and U-tube, can provide many examples of how to do said.
Once the tank is clean and the lines flushed and the filters replaced, life should be good.
I would fully expect that your fuel supply issues were directly related to the rust contamination, that stuff is murder on needle and seats and also very efficient at blocking small ports (and filters).

As to the 5th gear downshift on inclines, I suspect that once you sort all the issues it will become less extreme but is nature of the beast.
When I first started driving "Red" I was always shocked at the number of hills that would necessitate downshifting from 5th to 4th and sometimes even to 3rd.
Then I got my Suzy (4spd auto) and it occurred to me that even with 60% more power on tap, the damn thing downshifts like crazy at any hill.
You wouldn't ride a bicycle down a hill in 1st gear or up a hill in 10th, they have gears so that you can select the correct gear for the load.
Once I hoisted that tidbit and started aggressively downshifting (before the engine starts to struggle under the load) both of us were much happier.

The good news here is that you have made significant progress and a little more tweaking should yield a reliable ride.
Cheers
BB

[Burntboot]

Forgot about that sticky linkage - first you have to sort out WHY its sticking.

1st find out under what circumstance it sticks (part throttle, full throttle etc), once you can replicate the sticking, remove the throttle cable from the carb and try to recreate the problem without the cable attached.

If you cannot replicate, the issue is in the cable.
If you can replicate, the issue is in carb.
Being that the shaft runs thru the housing, care must be taken during assembly to ensure that all screws are evenly torqued including the base plate nuts.
It doesn't take much to cause a cross-shaft to bind, there could also be contamination on the shafts where they pass thru the body, or if you disassembled the butterflies from the shafts you may have reinstalled it "upside down" and now its binding inside the bore, that would require a full teardown so hopefully not the case.
Unfortunately the only way to discover what is causing the binding, is to keep disassembling till the problem disappears.

Oh and the reason for the 2 attachment points for the cable.
That "2nd" bell crank would be for the kick down cable if it had an automatic transmission.

BB

[m87]

Legend! Thanks for the answers BB.

I redid the numbers on my short trip by filling up (instead of guessing via the gauge), turns out it used 8 to 9 litres over 52km... far out. Also noticed that the exhaust smells different now, kind of tangier, less fuelly, which would be great if it weren't for the mysterious missing fuel. Dipstick still smells like oil, so I hope it's burning it. Loves being redlined in the lower gears now, possibly that's the only time it's getting enough air?

Warm idle is higher too, so I've decided to take it into the shop next week to let someone with 30+ years xp have a look over everything, and check the timing. From our short convo yesterday, it's likely that it's running rich, idle is high and timing is well wound back and possibly not advancing properly to boot. If they have PCV grommets I'll get them to put in the one I bought on ebay - the one that's in there is rock hard, and just won't yield the valve.

I also have a suspicion that if it's been this way for much longer than I've had it, the cat will be caked full of garbage, or nonexistent - so might have to solve for the new tank and back half of exhaust at the same time. Wouldn't mind getting something with more than 42L in the process :LOL2:

[m87]

Update: The shop is looking into it, and in checking the timing they've found that it's 'not resetting' - either properly or at all, I didn't ask, but from what I can Google up on the subject, it would explain why it loves higher RPM ranges and hates just a little touch of throttle. Heck yes, it seems we have a symptom beyond just "drinks like a fish".

Does anyone have experience with timing being out on these vans? Think it would account for the nasty 15L/100km consumption?

[Burntboot]

The distributor uses 2 sources to provide advance. The first being the mechanical weights/springs, as distributor speed increases, centrifugal force makes the weights move outward (retained by the springs), the 2nd portion of advance is provided by a vacuum operated dashpot (much like the one at the choke)
Now mechanical weights can very well seize if the system isn't regularly serviced. And if the vacuum pull-off isn't working, not only will it cause a vacuum leak but will also fail to provide advance at lower engine speeds.
I don't know if blocking off the secondary choke pull-off would have an effect on your current problem but that is also why when trying to solve a problem its best NOT to "modify" the system from original spec.
You will have to trace vacuum lines.... and figure that part out.
Lacking sufficient advance will hinder performance and may increase fuel consumption but don't know if it would explain 15L/
Sounds like you buggy has been neglected and working thru all systems will be required to sort it out.
That said, while it sounds onerous, it isn't really so bad.

Another thing to consider on timing would be to verify that the harmonic balancer hasn't slipped, the rubber bonding can let go and allow the outer ring of the balancer (with the timing mark) move in relation to the inner portion which is located to the crank via a woodruff key. While its a rather common problem on all makes (exacerbated by oil leaks on the front of the engine) for some reason most will fail to verify its integrity prior to making other diagnoses.

This is also the reason to do the detective work yourself.
A garage is always under the gun on time management, which makes a full interrogation difficult.
And because they are always aware of time, they may not dig as deep as you might, especially on a vehicle that they are not familiar with.

Everyone talks about how hard it is to work on our vans.
It is as much myth as reality.
While there are some things which are extremely difficult to access it is no more or less difficult the more "normal" designs.

Changing out the idler pulley (including time to press bearings out and in) took nearly an hour on Red (and about $50 parts)
When I did my wife's RAV4 idler, it looked easy and only took 4 hrs & $250 to swap out (theres a frame rail right in the way of the lower bolt so you have to either raise or drop the motor, lots of fun. And the "idler pulley" a non-serviceable assembly).

BB

[Burntboot]

Back when I had my Carbed Tercel, it had a little dashpot on the side of the carb, IIRC it was called an IAC valve?, I believe it affected fuel pressure under some conditions, don't really remember. Point being is that sometimes the diaphragm would rupture and allow raw fuel into the vapour system causing all sorts of ridiculous issues and super easy to overlook.
Just one more thing to watch out for.
BB

[Burntboot]

"in checking the timing they've found that it's 'not resetting' - either properly or at all"

Perhaps it is running advanced all the time or could be retarded all the time, but the statement doesn't make much sense to me.
At idle, with the vacuum advance disconnected and the line plugged, the mark should appear at the spec stated for your engine, usually that is somewhere int he 8-12* range but you need to verify what your van calls for.
Generally speaking as long as the advance weights aren't seized and the springs aren't deformed, they should work.
They can be checked with a timing light but significant revving in N is required and I generally try to avoid high revs under no load, especially on older vehicles
Once the base timing is set, you install the vacuum line to the dashpot and verify the timing advances a little (check the specs).


If it were me, I would start with ensuring the balancer is in good nik and not slipped.
If all good there, I would locate the engine at TDC #1 (firing) and pull the distributor and service it.

A timing light will be required but learning how to set your own timing is pretty easy and timing lights are dirt cheap these days (<$50).
I resisted buying one for years but never regretted the purchase, after the fact.

Once the timing is sorted out, go back and recheck the carb settings at idle.
Did you remove the cap over the mixture adjustment screw and how did you set the mixture screw?
BB

[m87]

:dance2:

Progress!

Took your advice BB, and looked into my 'mod' a bit more. Studied it in detail, and was able to jump the vac line instead of plugging it. No change on the running characteristics, but at least now I know it's fine.

After that I decided to get back to basics and delete all assumptions. Started with the air-fuel mixture screw... it was at the very least, 2 FULL TURNS too rich. FECK! It shouldn't have even been running let alone working ok 80% of the time! I had left it alone because I read about them being sensitive, and easy to mess up and given the van's performance under full throttle, I figured it was set fine.

Well, either the Liteace uses a super fine thread, or... I dunno. Either way, I screwed it in until it started to misfire, and then back enough to idle steady. Under this "YouTube tune" it actually SPAN THE WHEELS (accidentally) when I turned out of a laneway today. So much more bottom end, and best of all, it no longer stutters under very low throttle!

It's going back to the shop on Tuesday, I'll see if they have a gas analyser we can use to nail this one down...

Edit: The garage had looked and set the timing, which helped a bit, but it still had low-end issues. Will the mixture screw mess with timing? I guess not?

[m87]

I screwed it in until it started to misfire, and then back enough to idle steady.

So I did some more reading, and some people seem to use idle speed to indicate a good mixture screw setting. Went and played around with it, turns out the best idle is closer (hard to tell exactly) to the original setting, but if I go by the falter-then-back-until-good method, it's much leaner, closer to the point where I got the better low-end power.

Anyone know where I could find the factory "X turns back from gently seated"?

[Burntboot]

m87 - I don't have a manual for your carb so no idea what the right setting would be.
Am a little confused, are you saying that you did not remove the mixture screw while rebuilding?
If so, then the idle circuit has not been sufficiently cleaned, however...

As a general rule of thumb, I would start with 1-1.5 turns out from gently seated.
No, the idle mixture screw has no connection to ignition timing, that said, engine speed does.
Generally speaking getting a carb dialled in, involves a slow dance with all the settings. (base idle, mixture, timing)
The general rule on idle mixture setting is to run it in till the engine starts to stumble then back it till it smooths.
It is very important to make sure you allow sufficient time for everything to stabilize (30-60 sec should be sufficient) after making an adjustment.The easiest way to figure this stuff out is to gently run it home once you pull the plug, then you know roughly where stock was.
Probably would have helped to have that info earlier, eh?
The good news here is that you will know it, once you have it dialled in.
It will be that happy little sweet spot between not quite enough and clearly too much.

BB

[m87]

Thanks BB, I didn’t take it out. Haha amateur move number 243! Found a place in Sydney that can post me a replacement mixture screw when I get a sec to pull it right out and snap some photos/check for erosion.

ive set it a turn back from where it was stumbling at idle for now, and have a new temp gauge sensor on the way because the old one is either on 0 or halfway up - no in between. I figure if I’m accidentally running lean, I’ll want to catch those temps before they get too high (almost summer here!)

stopping by the shop for the diaphragm (that I don’t need now I can see it working) and to fix up the bill tomorrow, I’ll see what they make of it. In particular I’m interested in the solenoid here. If it is sticking closed, it would lean out idle, explaining why the rpm-based tune of mixture is actually so rich.

it did click when the ignition is turned to run, but I’m not so sure it’s actuating. It’s the only other thing in the idle loop thingy that I can think of re malfunction that would cause lean idle, balanced running.

good news is that I drove in city traffic and didn’t notice the fuel needle drop (yep, every 20 minutes at 15l/100km will drop the needle on a 40l tank! Yuck!).

[m87]

Oops, would help if I linked to the pic. http://members.toast.net/ahines/CARB3.gif

Not my exact carb, but close! Source and some good information here http://members.toast.net/ahines/Carbie_notes.htm

Mine is actually much closer to http://farm9.staticflickr.com/8025/7665311266_9ce49eb1df_z.jpg without the colors. From https://www.yotatech.com/forums/f116/86-22r-wont-start-unless-you-pour-fuel-carb-but-theres-fuel-carb-262743/

Good to have some visual indicators of this complex web of tubes!

[m87]

Well, guys at the shop are the nicest bunch I've met. No charge! We agree that it's likely that the idle circuit was running lean due to blockage/crustyness in the old carb, and so the previous owner may have tweaked the mixture on a lean circuit to highest RPM (or it simply rattled out, which is less likely thanks to the spring).

It's not pinging at high RPM, so it's not too lean for now, which is nice to hear, but I'll keep an eye on those temps just in case. See how we go over 150km later tonight.

For anyone else with a carburettor'd liteace, the '22r' pickup sold in the states appears to have a very similar carb setup (maybe these are 'Hilux' downunder?). You'll notice the similarities here Tuning Toyota PickUp Carburetor.
(https://www.youtube.com/watch?v=qn52mCTwOCY)
Also the mechanic said that tuning mixture screws to highest RPM is a good tweak for something you know 100% is running smoothly, but should never the way to set mixture when you don't know what condition the carb and most everything else is in. Good to know :)

[Burntboot]

Glad to hear its mostly sorted at this point.

You asked about solenoid valves, been awhile, but IIRC there are 2 types, some carbs have only the one solenoid, others have 2.
Generally speaking, if they click with 12V applied then they are good.
The O-ring on the end is indeed crucial to operation and have had a few where just installing a new O-ring solves the issue.
There are indeed two different types, one being a fuel-cut solenoid that shuts off fuel supply during deceleration, the other is to provide fuel to the idle circuit.
On the later style, I did have one that I couldn't source a replacement so we drilled and tapped it and ran a screw in to force the value into the open position.
Car did run a bit rich but no other real issues. Not saying you should modify yours, that was merely a stop-gap solution until we could source a replacement.

Given the amount of time this thing was running overly rich I would highly recommend doing a seafoam flush at next oil change.
All that excess fuel will have caused carbon build-up and that can cause other issues, so getting that potential issue out of the way is a good plan.

BB

[Burntboot]

As far mixture settings we always adjusted to the highest RPM (assuming idle stop and timing are correct) then dialled it back in 1/4 - 1/2 turn.
As you run thru your adjustments you will find the point where it runs best and noticeably worse, the set point should be somewhere in between but a little closer to "lean" setting than at max revs setting.

Essentially it is a coordinated dance between timing, base idle and idle mixture.
If the hardened cap was still over the mixture screw then no one has messed with it.
If the cap was missing, then theres a REALLY good chance someone was in there.
Back in the day, it was pretty standard practice to pull the cap and richen the mixture a tad, they are set as lean as possible at the factory which works great when its all new, but after things run in a slightly richer mixture makes for a much better driving experience.