post weber change, return fuel line

hi i have a 1991 1.8 carb engine code EX in my pride and joy!

however just wondering if i need the return fuel line from the vapour separator after installing a weber carb.

symptoms i have currently are as follows:
so after running my car until the engine is normal operating temp, and then i switch it off to go to the shops etc.
then when i come to start the car it struggles to get going, needing a tease of the pedal to eventually fire up :/
however if i turn the car off run in and out the shop it almost seems to start before i turn the key it is that quick!

i think it has something to do with the return line of the fuel system adding air into the system, when the engine is switched off.
this is backed up with the amount of bubbles running through the return line on start up.

my question is this, do i need it?
i read somewhere that the weber carb has provisions to mean i don't need the return line, but wanted to double check before removing it or clamping it off or does anyone know what else might be causing this?

thanks

you should be able to leave the fuel separator in place, sounds like you may have a pin hole in a fuel line or the separator has failed? I'd repalce all the rubber pipes see how it is.

worst case yes you can remove the separator entirely and clamp the return plenty have done this without problems

ok thank you

I put a second hand weber in my wife's cabby and did away with the seperator and capped the return. However the car seemed to be using a lot of fuel and wasn't running that great. It might have been the carb right enough. Anyway I put the seperator back along with the return and the car was running better and not using so much fuel.
Having just refurbished the carbs I know that the petrol being admitted to the bowl is regulated by a needle valve which is connected to the floats.

so would you say it wouldn't do any damage to the carb, over pressurising etc? i had a play with the tuning today, spoke to some garages and they said it sounds like its running rich. thought as i didn't really tune the carb when i first installed it i would try now, test drive tomorrow with some tools for adjustment!!

shouldnt do no, sounds liek you just need to tune it tho if runnign rich

The weber is notorious for vapour lock when used in an application with the carb above the exhaust manifold.

The heat from the manifold is boiling the fuel and venting via the hole in the top of the carb body hence it needs a pump of fuel from the accelerator pump circuit to get it going.

The vapour seperator and return line have no use when running a weber so you can remove it all.

In regards to tuning it first ensure it's jetted correctly. The carb is used on a wide range of engines all requiring different jets. It's not uncommon for it to have the wrong jets meaning no amount of primary circuit tuning will get it running properly.

I still have the vapour seperator pot on mine and return line to tank after change to a weber and it runs fine. The green accumulator on drivers side was removed though.

I would say its still a good idea to keep it, filters out any air bubbles in the fuel stream plus gives an extra reserve of fuel say if you are driving round a long corner and pump runs dry

The vented bowl on the weber is equally large enough to vent any air sucked in plus on a vehicle of this age with likely crud in the tank it's far from advisable to be letting a tank run low enough to be sucking air on corners.

Leaving it in place isn't an issue it's just not needed on a weber plus it just adds up to another point of failure and the reason everyone changes from the pierburg to a weber is because of the overly complicated design which once ages adds many points of failure.

awesome, thanks for all the replies! i have tuned the carb and it is running better now, however still required a bit of teasing with the throttle to get it going after going to the shop, may look at clamping the return line just to see what the difference is between having and not having it, just to clarify if that is the problem, never know my expectations for the time taken to start may just be too high!!