Changed fuel pump now runs terrible 79 350

[truckin 79]

The truck was hard to start after it sat and needed starting fluid most of the time to start. I thought to swap fuel pump out from 2 port to correct 3 port. I changed fuel pump to correct one with the 3 port type that has vapor line. The vapor line had a rubber hose on it uncovered. Could hooking this line up introduce crap into fuel pump or carb?

[Prong]

That third line is a fuel return to the tank, NOT the vapor canister. It should route back to a 6 port valve if you have dual tanks, or to the sending unit on the tank itself.

[truckin 79]

Well I feel like I opened a can of worms. The carb is flooding now so I took primary cover off and cleaned fuel bowl out which had some stuff in it. Funny thing is I just added a carb filter, I had just a universal filter before fuel pump. So I start truck and floods, so I plug 3rd line up and no difference. The carb is just flooding out, oh I did lower float in carb. I feel like I am in quicksand right now. I do have a 2nd tank but is not used in years, it is just a rusty mess. Should I switch back to a 2 port fuel pump

[truckin 79]

Well here is a update problem fixed. I was about to take hammer to carb because it kept flooding. I took carb apart twice thinking debris was keeping needle and seat from closing off fuel but both times I found nothing. I decided to swap fuel pump with return line 3port to the 2 port type and that made the difference. I don't know if 3 port was building extra pressure and fuel pushed past seat and caused flooding. Anyone know how to tell the difference between a vented gas cap and non vented. Next up an oil change since so much fuel washed past cylinders and ended up in oil.

[mongocanfly]

prong is correct...that 3rd line on your new pump is a return/bypass back to the tank...if you had a 2 port pump then you need to replace it with same..most likely caused your flooding issue..

[mongocanfly]

http://forums.aaca.org/topic/231394-...dentification/

[mongocanfly]

http://stant.com/index.php/english/p...tion-fuel-cap/

[truckin 79]

The truck does have two tanks and a valve selector but the drivers tank is just a tank in name only. I thought I was doing the right thing by switching out bad 2 port fuel pump for the correct 3 port fuel pump. My truck does have the return line(thanks Prong) but for some reason when I hooked that 3rd line to fuel pump it caused the flooding. I tried just blocking off return line and that still caused flooding. Actually switching out pump back to 2 port was the cure and I am still not sure why. I read on the net someone talking about pressure building up from non-vented caps. I didn't think it would turn into this just changing a mechanical fuel pump. I will say using a hack saw blade is the way to go changing chevy fuel pumps.

[Dead Parrot]

Don't dismiss the possibility that the 3 port pump put out too much pressure. QC seems lacking on a lot of parts. Other threads have reported pump pressures on the high side of 10psi.

I don't see how a properly working 3 port pump would cause flooding assuming the return line wasn't plugged somehow. Rust, dirt, nesting multi-legged critters. Wasps around here just love building mud nests in small tubes.

But if it is now running fine, don't touch it.