swampedout

I'm rebuilding a 1980 20r and I'm almost done. As with many things on this truck, I'm working with what the previous owner did and didn't leave me with.

1. On the stock Aisin carb, looking at it from the front, to the right of the main fuel inlet is another pipe pointed down. The previous owner had this routed back to the valve attached to the charcoal canister. Is this right? Anyone know what the pipe on the carb is called?

2. There is a hard line that comes up the frame from behind the charcoal canister and elbows under the bracket with all the VSVs on the fender. Previous owner had this capped. Anyone know what this one does? I'm going to trace it tomorrow but the mosquitoes are out so I'm done for the night.

old87yota

I am not that familiar with the 20R vacuum routing, so I am not much help.


Maybe you could post some pictures so we can see what you are working with, and someone might be able to see if you are missing anything.

One of the lines of the charcoal canister probably runs (or should run) to the fuel tank. The charcoal canister is supposed to store fuel vapor from the fuel tank and release it into the carburetor under certain conditions so the vapor is burned in the engine rather than vented to atmosphere.

13Swords

That pipe is the Fuel Vapor Return Port, and does route to the charcoal canister. It should be a pipe coming off the Fuel Bowl Cover.

The capped hard line coming from the rear of the truck is a Tank Vent/Fuel Vapor Line from the fuel tank. It is also supposed to be routed to the canister. I have no idea why this was capped off. It's supposed to send fuel vapors to the canister to be stored, so they can then be sent to the carb via vacuum line to be burned, under certain conditions, like cold start/running when a richer mixture is required.

swampedout

Theres plenty of "weird" things from the previous owner. Its a hard line that comes up along the fender and Ls between the battery and the shelf for the smog valves. Could i route it to the middle vacuum port on the charcoal canister?
Motors running fine. Slight misfire but i gotta let this project sit for a couple months. Moving out of state. And i gotta redo the timing cover. Something in theres dropping oil.

Btw 13swords ive watched (all) your videos. Very helpful for me working thru these gremlins.

13Swords

These trucks always have some weirdness from P.O.'s & some gremlins, but nothing that can't be put right. I am not exactly sure what you mean by "middle vacuum port" on the canister, but if you mean one of the larger ports on the canister, sure, you can do that. There should be 2 larger ports on top of the canister. One is for the vapor line from the carb, the other is intended for the vapor line from the tank. It doesn't matter which one you use for either, as they are both "intakes" so to speak, for fuel vapors to be stored in the canister. You are correct, the hard line on top of the fender is the tank vapor line. Also, just to clear up any confusion, when working properly, the "return lines" on these trucks only return fuel vapor, NOT any liquid fuel. If there is liquid fuel in those system lines there is a problem. Anything else you need to know about that system just message me. Also BTW, it can work just fine even without the electro/vacuum valves working. My truck is proof of that.

No idea about the misfire; done anything with the ignition system yet? Valve cover leaks - make sure you get the COMPLETE valve cover gasket set, which will have the 2 "half-moon" gaskets that go in the front & the back of the cylinder head. Most people overlook those. It would also be a good idea to completely replace the rubber grommet gaskets under the hold-down nuts. If you haven't already, don't forget to adjust your valves while you have the cover off. I adjust mine cold 2 thousandths bigger than spec because it's easier than doing it hot like the manual says to do. No valve noise & no problems doing this ever for me.

Thanks for the good words about the vids & I'm glad they helped you out. I don't consider myself an expert or a pro, but my posting those to Youtube was so others didn't have to go through what I did. I very glad that that was the result!

Good luck with the move & stay safe. Let me know in future if I can be of any other help.