MTCAMARO

iTrader: (1)

I'll keep this as short as possible,i've installed a new motor that isn't drilled for a mechanical fuel pump, so i went ahead and installed a carter p4070 at the back of the car behind the back seat and plumbed it into the 3/8 line.The pump runs but fuel isn't coming out the line at the carb,can hear faint gurgaling sounds though.Anyways,i realize that the mechanical pump i always ran before was pulling fuel from the smaller RETURN line.I'd never noticed this before,i've never had any fuel issues what so ever.
From what i can tell,the tank has never been out of the car,so i assume that the previous owner must have left the in-tank pump (car was a 2.8 multiport )where it was, and pulled fuel from the return line.I've never heard of anybody doing this on hear.I'm assuming the Carter pump i installed won't pull past the dead pump in the tank.
Later today,i'll get back under there and see if i can maybe replumb the intake to the carter into the smaller line and see what happens.From what i have seen,the return line is just a bit smaller and runs parallel to the feed line to the bottom of the tank.Hopefully the pump will prime and work normally...I'd appreciate any feedback on this problem as i'd like to fire this new engine this weekend.Thanks for reading .

built91Z28

I dont think you can pull from the return line. It doesnt go to the bottom of the tank, it only goes in the tank a few inches at best. I'm also fairly sure the smaller line is the feed line. Trace the line from the fuel filter to the motor. This is your feed line.

It will pull through an in tank pump. My brothers truck has been doing this for over a year now.

MTCAMARO

iTrader: (1)

The 3/8 fuel line IS the one that goes to the fuel filter on my car.I was pretty sure the bigger line was the feed line.I'm gonna crawl back under there and do some more looking around.thanks for the reply.

MTCAMARO

iTrader: (1)

Update:I got back under the car to verify that indeed the 3/8 line is the feed line that runs to the fuel filter.My Carter pump simply won't pull past the dead pump that must still be in there.I hooked the intake of the Carter pump to the return line and it pumped fuel almost instantly.I had a gallon gas can on the other end and it half filled it in just a few seconds.I'm pretty confident the return line must go to the bottom of the tank because i've run the car pretty low on gas and never run out of fuel in the 15 years i've owned it.My car has been getting it's fuel from the return line all this time with just a block mounted mechanical pump and i've never had fuel starvation problems.I'm glad i always ran a inline filter just before the carb though.
It might not be the right way to do it,but if a third-genner is going from fuel injection to carb,you can pull plenty of fuel for a mild smallblock from the return line and not have to drop your tank to remove the intank pump.I've been doing it since 1995,I just didn't know it untill now.
I didn't think this car had any more secrets for me but i guess i was wrong.

five7kid

iTrader: (14)

Take a look at the carb pick-up sticky https://www.thirdgen.org/forums/carb...nk-pickup.html . The tube the pump mounts to is the return line.

It's not a good idea to not have at least a strainer before the pump. You may have gotten away with it, but that says more about your luck than it does about the technical wisdom of the approach.

MTCAMARO

iTrader: (1)

I agree with you 100%.I had no idea i was getting fuel from the wrong line until i went to install this electric pump.Rest assured, i added an inline filter before the pump i just installed.If i drop the tank in the future,i would like to set things up like the link shows.Thanks for your insight.

PV9685

Nice post - good info. I am in process of the carb swap.. except that someone on eBay sold me a seized holley Red electric fuel pump... now I have to try to get some money back for that paperweight.

Though it looks like electric may not be the way to go -I am finding claims that regular carb-psi fuel pumps from the aftermarket don't generally like to pump all the time (ie: more for strip than street.... ?).

I am thinking of going with a mechanical pump and might just get a cheapy $18 mechanical pump by Airtex or similar rated at 40GPH.

Only two things - I need to fist find out if my 89 305 TPI block is actually drilled for the pushrod and; figure out if I need the "stock" or bronze pushrod... ? I can look down at the cam right now because the manifold is off, but I can't tell cast vs. billet... and then I guess some cams have hardened lobes.. etc. blah! I don't know but it kinda sucks when you're in the midst of things. This swap has been very easy so far but, I don't think it's the kind of swap to rush through.

I hate the thought of improvising too much - except the return line "trick". I imagined that like others, ours probably went close to the bottom. I would rather drive for even just a little while off the return, than drop the tank right now. I thought the tank was bad in a GM FWD car but... DARN! lol

I think the return line with a screen type filter before the fuel pump would be an adequate method for testing and "potentially-unrelieable" long term operation. Regardless, I'll be trying it soon.

But, just like the other postings say... for the long run it's only proper to do a good carb sump. But I'm wondering if come fuelpumps have problems with air in the lines from the way the lines go?