SilverBullet73

iTrader: (2)

Ok, my fuel pump took a dump on me a few months ago. The car was sitting for a while trying to get all the stuff. When I got the car it had an impala tank stuffed into already from the previous owner. I didn't like the idea of the impala tank since the Grand National tanks are a direct swap (what was the guy thinking??) So I bought a new tank, sender and a nice walbro 340 pump and a Grand National hot wire kit from racetronix to keep the voltage optimum for the pump. I installed the tank and connected the feed and return and connected the vapor line but previous owner just plugged the line by the engine compartment. So as I'm letting the car warmup to check for leaks, everything is looking good, but then the vapor line starts leaking gas!! What the hell?!? So I figure I need a charcoal canister and the evap purge to make it run right. In the meantime I figure I'll unplug it and put a breather on the line so the pressure won't build up. It's still spewing gas when the car warms up. When I open the gas cap, there's alot of pressure build up. What can be causing this?!? I'm at a loss since the previous setup ran with no problems. If it helps the gas tank currently has about 1/4 tank or less of gas. Sorry for the length, just trying to explain thoroughly. I'm at a loss?!? Please help!

Old Geezer

iTrader: (3)

Still spewing after you unplugged the line and added a filter??
If so, look at the filter you used. Is it a one way flow??
Hoses not crossed at the tank?

SilverBullet73

iTrader: (2)

Lines aren't crossed, would spew out fuel right from key on position, only does it after pressure builds, or to clarify, after the car warms up. As for the filter, I only used an open element type breather filter to let the vapors out, is this incorrect?

SilverBullet73

iTrader: (2)

Wow, nobody knows? I've searched around and don't see anything on this. Doesn't make any sense. Guess I'm going to have to play around with it till I get it right. I'm open to some theories, anyone?

TomH

iTrader: (1)

Try swapping the vapor and return lines.

If you have them crossed, any pressure build up will pump fuel instead of vapor into the canister.

Good luck.

SilverBullet73

iTrader: (2)

Ok, problem solved! I feel like a moron though because the lines were crossed, lol. When I took the old tank off, I just connected everything with the new tank according to the hose sizing. Well, turns out that the return line on the new sending unit is 1/4" and the vapor line is 5/16", doh! Also found out that at cold start and key on, not much fuel runs back from the return line. Once closed loop begins, fuel starts to trickle back the return line. I always thought fuel recirculated continuously right from key on. Anyways thanks to all who helped. The car runs great now and is back on the road finally!

Old Geezer

iTrader: (3)

Likely at key on, cold, the system is not completely full, and the short time the prime is activated, there's not enuf flow to create back flow volume.
@ idle, there should be a goodly amt of fuel returning.. Like 90+% of the pump volume will go back to the tank.
If it's only a trickle, I'd be looking at fuel pressure while U R driving!!