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

[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!

[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

[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. 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 and this kit. 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!

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!