I got a "new" 86 (that had a bad engine and ran like crap) and just put an engine in it. I'm having troubles getting it to run well when hot and/or under load. I noticed that when I rev it, the vacuum line from the throttle body to the charcoal canister jumps. I plugged both ports and now it runs pretty well.

Backing up a bit, when I brought the truck home, on a hot day (and it was running like crap), it had gas dripping feverishly out of the bottom of the charcoal canister. I checked the fuel lines back to the tank to ensure that the lines were hooked correctly. I will check the canister tomorrow according to the FSM, but does this sound like the symptoms of a bad canister?

 

Too tough?

So far, it appears that the charcoal canister had problems. I grabbed another one, cleaned it per the FSM, stuck it on and reinstalled the vacuum lines. The engine now runs like a top.

I haven't tested the old canister. I set it upright against the wall, and it dripped gas out of the bottom for quite a while.

 

good deal, sounds like you figured er out. Did you happen to find any reason in particular why the canister was plugged or you just figure it was old??

 

sounds like the canister sucked some gas out of the fuel tank somehow, and the engine ran like crap cause it was too rich sucking too much vapor or raw gas form the canister. I think there might be a valve back by the fuel tank (or in it above the fuel pump on the mounting plate-best to check the FSM)to prevent raw gas going up the char canister lines . . . maybe the tank was filled over the level of the charcoal canister hard line inside the tank . . .

 

I haven't checked it yet. I figured I would wait for the canister to clear of gas a bit first.

This truck has an extra tank (gravity feed) on it, and it had just been filled so maybe the extra pressure contributed to the problem?

 

I'll have to check into that. The dumb gravity feed tank could possibly make the main tank too full.

I've never run into this issue before except once on a vehicle where the lines at the tank were reversed.

 

The gravity feed tank makes a difference. I just bought one a while ago but still haven't installed it. The factory evap fitting at the fuel tank needs to be plugged, the line going to the charcoal canister goes to the plastic "dome" thing on top of the aux tank. That way the canister only gets vapors since it's connected to the highest point of the system. You might want to go through the rest of the line connections to make sure it was hooked up right.

Here's the instructions I recently got from them for my '88 4runner, you want to look at steps 15, 16 & 17 - wish they had pics or diagrams . . . . I'm trying to work out a system to use a pump instead of the gravity feed with the fitting on the bottom of the tank - looks like a 2 or 3 psi pressure switch (from Summit) on the pressure side of the pump controlling the relay, I can get that minor pressure with a slight restriction before the main tank - so when the aux tank is empty, pressure drops and the pump turns off

 

Thanks for the info. I'll have to check the auxiliary tank to see if it has a fitting on the top. I think the tank was made by Auxiliary Fuel Systems or something like that from Hemet, CA.

 

I checked and the evap fitting on the top of aux. tank is tied into the fuel fill vent hoses. Oops. The evap fitting on aux tank runs back and tees into a small fitting (fuel fill vent) on the side of the tank, which then runs up and tees with the main fuel fill vent hose.

 

Update: the evap fitting is on the top rear of my aux tank and unfortunately is lower than the fill vent fitting. Of course I saw this only after unhooking the hoses to "fix" their routing. I said screw it and reattached the hoses as they were.

I am thinking of replacing the fuel hose at the canister with a longer one with a couple of loops with the thought that it might make liquid less likely to enter the canister. For now, I'm just trying not to store gas in the aux tank.