Gas coming back up filler neck

udubrx7

My car (89 dx with d16a6) wouldn't start this morning so I swapped out the ignition coil (found a little crack in the plastic housing) and decided to remove the evap cannister because I thought it might be a fuel problem. After that the car still acted the same, but after I floored it and turned it over for about 8 seconds straight it finally sputtered to life, ran like shit for a few seconds, then started to run normally. I just checked the fuel pressure and did the test on the fuel pressure regulator, everything seems to fine.

Now onto my very strange problem.... I thought maybe the car had been low on gas, so I went and filled up a 5 gallon gas can. When I took off the gas cap to try and put some gas in there, gas came gurgling up the filler neck and started pouring out onto the car! I also noticed that the longer the car runs for, the more quickly the gas gets expelled from the filler neck. So I guess somehow the gas tank is getting pressurized by air and is not able to let it escape? When I removed the evap canister I left the line going into the firewall open so it could vent, I ran my last civic this way for years with no problems. I plugged the intake manifold nipple that is now not used, as well as the nipple on the evap solenoid. I don't have my jack and stands here at the house, or I would go ahead and drop the gas tank down and take a look around at the hoses.

Does anybody know what could cause gas to forcefully come out of the filler neck like this? I'm also confused as to why the open hard line that goes through the firewall from the evap can isn't letting this pressure out of the system.

udubrx7

Update: I reinstalled the charcoal can, but it didn't seem to do anything. I unhooked the line from the charcoal can that goes back through the firewall, and blew air through it. That caused more gas to start rushing out of the filler neck (with the gas cap off). So I decided to put some vacuum on that hose using my mityvac. That caused the gas to drain back down into the tank very quickly, leaving the filler neck dry. I hooked the can back up, and let the car idle for about 20 min with the gas cap on, then pulled the cap off.... no gas came gushing out!!! WOO HOO!!

Not really sure what the problem was, but I drove the car around for about 20 more minutes and there was still no gas trying to escape the filler neck when I take the cap off. Also now my fuel gauge has seemingly started to work (usually it either just says half a tank or totally empty - either way it is wrong) and is registering 3/4 of a tank. Weird.

leWolf

Wow, that sounds like a real mess and dropping the tank would really suck. Good thing it magically got fixed.

Haydz

One piece of advice i can give is stop doing more than one modification at a time. The more you change, the more you have to diagnose.

udubrx7

Of course.... that's why I didn't do more than one thing at a time. That's one of the first things I learned from my Dad about working on cars ~15 years ago.