Sdb8100

Hello All,

Here's the truck details:

• 1985 Pickup 4x4 22r engine 12K on miles fully rebuilt.
• Emission equip still installed and all vacuum lines checked and correct.
• New wires/plugs/ignitor & coil 1yr old +/-
• Remanned Aisin Carb purchased and installed 5+ years ago [not by me].
• Replaced aap diaphragm 1 year ago [small breech]
• Fuel pump replaced 1 year and works fine.

Initial Symptoms:
I would start truck [very easily] and it would run for 3 seconds and cut out. It would then be a hard start [many cranks] and it would fire up. No issues after that. Drives well/idles well/ Gets me home. Next day or two or a week, [it varies] go to start truck in the AM and immediately it would fire up fast then cut out after 1 second. Then it wouldn't start. Crank-crank-crank. Nothing. What I did.

• Fuel window is on center line.
• Pump working just fine.
• Looked at each spark plug and cleaned. Cyl # 4 only was a little wet and gassy smell, the others not as bad. I'm getting spark.
• Hooked everything back up and after some cranking it fired up! Then ran fine and started fine for a week.

Then it happened AGAIN. Went through same process. Couldn't start it.

• Let it sit over night. Noticed fuel bowl empty from the half way point. Assumed it was leaking into manifold as there's no external fuel leak.
• Finally got it started after a lot of cranking, airing out cyl and plugs.

Now it ran like complete crap. Rough. Backfire from carb. Fuel window when running is now almost full. Won't drive.

I took carb off vehicle to investigate. Will post more info on investigation efforts, but let me know your thoughts.

Sdb8100

UPDATE:
When I pulled the carb off the manifold I did notice the insulator block was wet on one side [signs of leakage, maybe?]. I also didn't notice any separate gaskets on the insulator block top or bottom. I know they exist as I've seen replacements and images online. Would my insulator block have integrated gasket material? It's not obvious if it does.

I filled the float bowl and let it sit for half a day on the workbench to see if 1) any gas drained out and how much. 2) what was the source of the leak. After testing and retesting, the float bowl did leak gas. I have the upper most portion of the carb separated. The top surface of the carb was damp with fuel all over [see image]. The slow jet had fuel pooled in the recess. The one barrel pointed out in the image had fuel coating the walls and butterfly. I could not tell the exact source. How would fuel get from the float bowl to the top surface just sitting there? I don't understand all the different routing.

user 82300

I will have to dig around for some how tos i wrote up on paper for the oem asian carbs. After some years i upgraded to the weber 32/36 carb. They make a manual choke, electric choke, and a carb, smog legal version of each. I went to that in like 2015-2016 and never looked back. If you struggle with this carb compare the price/work. I sent my asian to be rebuilt and never quite got it to run right even after a skilled yota shop took it and they said hey "the asian carbs run amazing when they run, but when they fail they are hard to get right again" so i went with weber and it was less work/fuss. So just an alternative. LCEPerformance sells the kits that are complete if you are unable to figure out your situation.

Sdb8100

I should also mention that I am building a 5VZFE to swap into this truck... so short-term is to get her back working again so I can drive her until I'm ready to take her off the road for a bit of a resto. That'll prob happen within the next year. I figured that I'd investigate and see if I can pinpoint anything that may help future float bowl leakers.

user 82300

I would replace the gasket between the fuel bowl and throttle plates

Make sure the valve seat for the jet isnt leaking

Worn float needle is actually kind of common

Make sure the site glass isn't leaking too

Also the fuel shut off solenoid can leak

check valve in fuel pump failing allowing gas to gravity feed out

99% you have a leaking gasket or a crack inside though

Sdb8100

• Gasket b/t the fuel bowl and throttle plate will be a next investigation. Good call.
• Fuel pump is fully operational, [tested]
• Float needle taken out of the equation and still leak. Not likely main issue, but will check its condition closer.
• Checked fuel shut off solenoid. Functions fine after testing per FSM. No external leaking. Will replace gasket[s] to take out of the equation.
• site glass not leaking [externally] will change oring gasket to take out of equation.
• How can one check for a crack housing?? [Other than visual inspection]

thanks for your comments/insight.

user 82300

I usually carb clean or brake clean the crap out of it and let it dry then yes feel for ridges/sharp edges and look at it with different lighting etc.

Sdb8100

So I could not pinpoint the source of the leak like so many others. I’m still investigating but my time has been adjusted to focus on installing a new carb and doing some emissions delete.