I've got a 22RE and when I go to start it, it turns over for a while before actually starting. Once it starts I have to keep the RPM's up a little to warm it before it will idle by itself. Let it run for 10 minutes turn off and immediately try to start back and it seems to loose prime that fast. Once starting again have to pedal for a second to get it going. Seems to run and drive fine but it does idle between 11-1600 RPM's once running. Any ideas on what could be going on?
Also it builds up pressure in tank and leaks fuel out of the drain tube from bottom of charcoal filter. Only way to get it to stop it loosen gas cap and relieve pressure.

 

Here is how to check the canister & TVV: http://web.archive.org/web/201003261...76evaporat.pdf

Also, make sure return line from the FPR to the tank is not clogged

 

My 1979 pick-up evap CC is SOAKED with fuel and was draining into the chassis rail where the bottom vent Is routed. I removed the CC, the TSVS, plugged the vac line and capped the plenum and put an in-line fuel filter on the vent pipe from the gas tank. After shutting down (running for 10 minutes) gas bubbled up the tank vent pipe and about an ounce of gas spat into the filter. Did the same with gas cap off - nothing happened. What’s going on? Quick temp fix: drilled small hole in cheap replacement gas cap.

 

Your gas cap allows air to vent IN (to keep the tank from being crushed as fuel is pumped out), but does not allow fumes to vent OUT (The HC in gasoline fumes was a huge contributor to smog.)

So the fumes should go into the Evap Canister where there are held just until the engine runs again. Then the fumes are sucked out through the TVV (Thermal Vacuum Valve) and burned in the engine. The TVV doesn't open until the engine warms up, to limit rough running when cold. That doesn't take long.

My guess is that you have a cross-leak in your fuel tank vent line, so that pressure in the tank pushes not just fumes, but liquid fuel, into the Evap Canister. Or, your line through the TVV is clogged so that the fumes are not getting sucked out of the canister; they condense into liquid there and leak out the canister air-in line at the bottom. Drilling a hole in the gas cap does two things. It allows you to pollute the air where ever you go. More importantly, if you get in a minor re-ender, gasoline will spray out of the hole in the gas cap (the gas cap is part of the safety system). Once that spray ignites, it will flash back into the tank (the tank is full of an air/fuel mixture, in addition to liquid fuel), for an unforgettable show.

 

Thx Scope103 - vented gas cap reinstalled. So, after scrobbeting about under the rear cross member and top of the gas tank it is clear the the PO (AKA “The Bodger”) connected the emission evap line to the fuel return, and the fuel return to the emissions at the mid-way soft hose connectors. I think that pretty much explains everything. Thoughts?

 

Hey, good job! Your fuel return was pushing enough fuel into the vapor line, that when you stopped and the vapor pressure increased, it pushed it into the canister. Well, that's my guess.
On the 2d gens, the TVV is dealer item, and about $60-$90 ish. You might be able to bypass it (running the vacuum line straight to the throttle body) if you can tolerate a little rough running when cold.

I don't know much about a '79, so take my specifics as only approximate.

 

Good catch!

The evap line is plumbed at the top of the tank and the fuel return to the bottom, so swapping these under the vehicle gives exactly the symptoms you had.

The quick test is to shoot some air into the evap lines to the tank and listen for bubbles thru the filler neck.

 

Co_94_PU - On my 97 RN37 the vent and main fuel lines run to a double-outlet plate on the front/top of the tank, the evap goes to a higher/centered single-outlet plate so easy to switch the double outlet at the hard line to soft tube intersection, as the routing is well-hidden above a cross-member and the tank itself.

Reversal happened at the red circle as both lines come out from above the x-member onto the floor pan

 

(Note to self: "Don't buy a truck from anyone named The Bodger.")