Miked85

I recently discovered my aap diaphragm went bad. So I decided to go all the way and have my intake sand blasted and dunked. I then rebuilt the carburetor. Put it back together, tuned it. It starts right up, high idle kicks on. Kicks off when warned up, idles beautifully. Throttle response seems perfect at idle. Once I start to drive it hesitates then picks back and will continue to hesitate as I push in the throttle until 2800 rpms. It seems to run great after that. It seems to me it's flooding until its able to burn what's thrown at it. Sight glass is at the middle top range. Anybody have any ideas? The truck ran fine before rebuild.

slow-mo

Did you re-use the existing main jet or did you replace it with the carburetor kit?

Confirm that the distributor vacuum lines are correct going to the correct vacuum source.

Confirm that the main mechanical Accelerator Pump is squirting fuel into the primary barrel when operating the throttle linkage by hand.

Miked85

The kit did not come with jets, the accelerator pumps good. I looked back at the schematic on the carburetor and started question the spring for the aap diaphragm. Took it apart tonight what do you know, put it on the wrong side on the diaphragm.. It picks up and goes as it should now. It did give me crap for a second when I put my foot to the floor in 2nd gear doing 20mph. Why do you ask about the main jet? Thanks for your advice, I appreciate it.
- mike

Miked85

It still does my original complaint. I'm wondering if I put the float needle vale in improperly.

slow-mo

The main jet between California & Federal is a different size, not a lot but different. I was checking to see if you had you had used the main jet in the carb kit and that was causing this issue.


Once the engine coolant reaches normal operating temperature the Bi-metal Vacuum Switch Valve (BVSV) that routes the vacuum to the AAP would shut off. So that's probably why the spring on the AAP did not correct the issue. Once the carburetor kick down high idle to normal idle, the AAP is non-functioning.

If the fuel level is in the middle of the sight glass while the engine is running and stays there, then float needle valve is opperating correctly.


I suspect, but you will have to confirm, your main Accelerator Pump is malfuctioning. Either by the same incorrectly spring installtion or maybe by a clogged passageway within the carburetor itself. From your description, it sounds like the engine is not getting enough fuel at the moment of acceleration. That's why I had stated to confirm that there is fuel coming out of the accelerator jet in the primary barrel.


Can I assume you installed the Power Valve & Power Piston correctly?

slow-mo

OK, I missed this statement before I posted the one prior to this.

Skip what I said above since you have already verified that fuel is squirting out of the accelerator jet.

Miked85

Its a california truck, there were no jets with the kit. Toyota or napa cant get new jets either, but there isnt anything wrong with the jets. I blew out all of the passage ways twice after rebuild. After two weeks, i had realized i did not set the spring on the metering needle. I havent driven the truck pass the drive way, but it did not buck on me once i put the engine under load. Will say soon if i have solved the original problem. I also had replaced the choke diaphragm and now it wont kick down off of high idle. Been trying to find a schematic or some type of explanation as to how to set the spring within the electric choke with the choke arm assembly. I have figured out four ways on how its not supposed to be assembled. Lol. Hoping to find a solution soon, i dont have 100s of dollars for the local mechanic dick to take me in circles. lol Any help would be appreciated.

slow-mo

You can check it by applying vacuum from a vacuum hand pump and seeing if it holds the vacuum.

The only other thing besides a faulty vacuum diaphragm is that when the engine coolant reaches operating temperature, the Bi-metal Vacuum Switch Valve (BVSV) does not switch the vacuum to that Choke Pull Off mechanism to physically remove whatever is left of the choke setting. You may have a faulty BVSV. The way to check for it operating correctly is connect a vacuum gauge to that rubber hose going to the Choke Pull Off (the choke diaphrgm) and start the engine cold. After the engine coolant reaches a set temperature, vacuum is supposed to be routed to that hose, therfore you'll see the vacuum gauge register a vacuum.

That choke diaphragm does two things, both at the same time as the linkages are interconnected. One is to remove what is left of a progressively openning choke and two, it removes the Fast Idle Cam. The choke coil itself will slowly begin to open the choke plate via 12 volt power going to it. But may not be fully opened when the set operating temperature is reached. That's when that BVSV forcibly kicks off the rest of the choke.


Yep, that's where taking lots and lots of pictures prior to the disassembly pays off.

I'll see if I have any, but it wont be untill I get home from later today. I'll see if I can post up something later on today or tomorrow.

Miked85

Everything checked out. I was able to assemble the electronic choke, apparently the arm coming off of the choke butterfly wouldn't sit properly due to improper installation on my end. I recommend not messing with that stuff after having worked a 9 hour day. I was in such a rush to finish, i was forgetting to think things through before i acted. Truck runs great now though. Minus when its warm, i have to put my foot to the floor in order for it to start. From what ive read, i shouldnt have to do that. It also seems to take alittle longer then normal to get past 3rd gear. I wouldn't say its hesitating, but just a little slow. But they are gutless wonders. lol That may just be the butterfly angles on the carburetor though. Not entirely sure, i would like to do an efi swap this coming summer. Just need to find me a donor. Thanks for your help slow mo. I appreciate it.

slow-mo

What's common after a rebuild is that the carburetor will leak fuel into the intake manifold causing hard restarts as a result of the engine being flooded.

The way your restarting the engine is correct, press and hold the gas pedal all the way to the floor to allow maximum air into the cylinders until it wants to start.



There's a guy over in forum 116 (1986+ trucks) who bought a new carburetor from a Chinese manufacture off eBay. So far he seems to like it.

https://www.yotatech.com/forums/f116...t-carb-263287/

Miked85

Interesting, wonder why it would automatically leak. You would think after replacing all of the gaskets, there would be no leaks. Yea I thought about a new carburetor, but I'm into wheeling and carbs and steep angles don't get along. So I am going to keep a look out for a wrecked efi. Swap everything over.

timothy47129

I'm the guy that bought the new carb from china and I have no complaints.its a stock replacement carb not an Asian but an exact duplicate .i have heard the stock carbs do pretty good at off road angles if the floats properly set.but idk.i was gonna do the efi swap but it wasn't cost effective for me.having to find a good gas tank.a ecu , wiring harness ,gas lines and all the sensors.the junkyard wanted an arm an a leg for all of it.your best bet would be to find an individual or buy a whole truck and part it out when your swaps done . Good luck

hashwin

I've had an '86 22r almost forever. Very reliable, just as you'd expect. But lately, she's developed a sort of random stutter in the fairly low rpm where these motors torque & even a stumble just starting out (it's 2wd & I'm not a 'secondary' type driver). Doesn't really matter if acc or steady throttle, it can completely spaz out.
It starts up fine (well, the float bowl drains overnight, what's that about?) and the choke/fast idle aspect works fine. Once it's half warm, the trouble begins. My acc pump works, and I neutered the AAP years ago, didn't need it. I took off the carb top and blew out everything I could find. There wasn't anything significant in there.
There doesn't seem to be a lot of info on the power valve/piston thingy, it's often mentioned as a sort of third accel pump, but it looks to me like it's playing, even at a constant throttle opening, since it's controlled by vacuum from a port under the throttle. As slo-mo mentioned, it's the only primary fuel that doesn't go through the main jet, and I'm wondering if I might have missed some goop in the passage that leads to the venturi. It appears that the spring in the piston holds it open, and more vacuum tends to close it.
Although it's possible that it's actually an ignition problem, the temperature thing makes me suspect the carb, unless the ignition is so frail that it can't fire once the mixture leans out. Once it's completely warm, the stumble is less, but there's still a lack of strong firing. Could this be a power valve thing?
Thanks, folks!