mike55

I have narrowed my empty fuel bowl to the accelerator port in the main barrel. I cannot figure out why tho. Seems to come out a LOT faster when hot. Diagram seems to show the accelerator pump weight(or needle) with a spring. There is no way to remove these though. I am wondering if these are not seating and allowing fuel to siphon out by capillary action. Can some one please tell me how to remove these springs and needles(balls or maybe even a rubber gasket)
Will post pic when I figure out how

mike55

These springs have caps on top, not screws. Just smooth caps like the idle adj screw<br/>

mike55

Picture with airhorn removed. Passenger side of carb. Tube at top left is acc outlet into barrel.

mike55

Also, it's a 1987 22r, rebuilt carb. Soaked overnight, fuel bowl was emptying BEFORE I rebuilt it. Was hoping to get lucky and fix that with a rebuild, by no dice. Truck runs great after it runs a few seconds(30 or so) and burns off all the fuel that leaked into the intake manifold.

mike55

Any ideas of this would cause fuel to seap out of the bowl? Or how to remove the springs to check it out? Anyone?

slow-mo

That has been the $64,000 question (for those that know that game show) on this forum. Very frequently after a DIY rebuild, the stock carb will leak fuel from the bowl. It did with mine, and many others on this forum. After many hours pondering why this happens and considering how this could happen, after opening up the carburetor, I gave up.

I also thought of the capillary action too. The reason why I dismissed those ports is that the fuel would have to travel uphill, against gravity, to exit out the respective port in the carburetor. So that would be from capillary action or some kind of percolation action.

What I also thought of was some kind of residual vacuum under the throttle plate that caused enough pressure differential (low pressure/vacuum) to allow the fuel to continue to flow out of the bowl. And then once it continues to flow, it acts the same way as siphoning fuel out of a fuel tank with a garden hose.


As you've found out, those caps are pressed in. No servicing available.

mike55

I know everyone has the same problem. Mine was doing this before the rebuild also. BUT I have definitely verfied that the fuel IS coming from this acc port with the engine off. It is worse when hot, it actually will drain in a few minutes. I have not saw where anyone pinpointed the source of the draining. Now that I have it pinpointed I was hoping to find someone smarter than me for guidance. I guess no one has ever drilled these caps out to inspect the spring/seals under them. I will try and locate a old busted one and do a test drill on it.
Thanks

mike55

Just to update my own post. I never found a solution. The OEM carb would drain into the intake and flood the engine over night, within minutes if engine was hot. I removed the plugs in the above picture. There is a very light spring and bb under each cap. I drilled a small hole dead center of the cap and then pried it out with a sharp tool. I installed a soft rivet the same size as the hole i drilled. The carb ran fine after, but still leaked. I tried different size BBs to no help. Anyways i recently swapped to a weber 32/36 and am currently working on tuning it correctly.

old87yota

Thanks for the update!

Too bad you couldn't figure out the problem. My carburetor also has this fuel bowl drain problem, although my drain problem takes hours when hot, not minutes, so not as bad as your problem. I recently bought a used Aisan carburetor to play around with and will rebuild. Maybe I can do some experiments to try to get an understanding of this problem.

This is the major elusive downfall to these carburetors. Other than that, I think the factory Aisan carburetors are great carburetors!

Happy Holidays!