Fuel inlet info sought

[HandyAndy]

Hi all,

I,m looking at connecting up the installed fuel line to my carb ( standard carb setup) on my CVH,
my question is this.........

Do i NEED to run a return fuel line back to the tank from the fuel vapour seperator or can i ditch the seperator ( its in the engine bay) , or keep it in place & just run a short return line from the seperator & "T" it into the fuel line that feeds the fuel pump (which is attached to the top of then engine)?

your thoughts/suggestions are welcomed.

The reason i,m asking is that i intend to run bike carbs so won,t need a return back to the tank, so i,m being both lazy & forward thinking :D

cheers
andy

[twinturbo]

I would put the return in, i think the vapour preasure trap is there to prevent the carb being over preasured which may lead to the car running rich.

And anyway. when yo step up from the bike carbs to the throttle body injection on megasquirt your going to need the return ;)

TT

[gus]

Hi Andy,

I had the same discussion with AdrianH. We both threw the vapour serperator in the bin. Mine runs fine without it.

Like you said I have looked at running bike carbs in the future, and by using a bike interrupter fuel pump you don't need the return to the tank.

I wouldn't both with it in my opinion.

Cheers

Gus

[HandyAndy]

Hi Andy,

I had the same discussion with AdrianH. We both threw the vapour serperator in the bin. Mine runs fine without it.

Like you said I have looked at running bike carbs in the future, and by using a bike interrupter fuel pump you don't need the return to the tank.

I wouldn't both with it in my opinion.

Cheers

Gus

cheers "Gus",

that was my thoughts, but just wanted someones opinion on whether i,m thinking right :D

so , are you saying to just run the fuel line straight into the fuel pump & ditch the seperator all together?
thanks for your help

Twin Turbo.....

That also was on my mind but then thought that the carb wouldn,t get under pressure as any surplus fuel vapour would still be in the fuel seperator but fed straight back into the fuel line going into the fuel pump, instead of travelling all the way back to the tank, if that makes sense. tho i might be wrong:o

cheers
andy

[gus]

Andy,

I ran the pipe from the tank through a filter & then onto the pump. From the pump straight onto the carb.

I think this is what most people will say. I think I have seen this come up on LCB builders before, and they all say to bin it.

Cheers

Gus

[HandyAndy]

Andy,

I ran the pipe from the tank through a filter & then onto the pump. From the pump straight onto the carb.

I think this is what most people will say. I think I have seen this come up on LCB builders before, and they all say to bin it.

Cheers

Gus

cheers Gus,

just what i wanted to hear (read) :cool:

thanks for your help.

cheers
andy:)

[baz-r]

the pierburg 2e3 (sierra cvh carb) shuold be fitted with a return line you dont need the seperator just a t pice with a restristion on the return side (old carb jet screwed in)
if you have no return line you will get one of two problems the float will hold back the pressure and the fuel pump will not follow the cam damaging it
or the float will get pushed down changing your fuel hight in the float chamber

also worth thinking about vapor lock in hot weather

[HandyAndy]

the pierburg 2e3 (sierra cvh carb) shuold be fitted with a return line you dont need the seperator just a t pice with a restristion on the return side (old carb jet screwed in)
if you have no return line you will get one of two problems the float will hold back the pressure and the fuel pump will not follow the cam damaging it
or the float will get pushed down changing your fuel hight in the float chamber

also worth thinking about vapor lock in hot weather

so, a return from the carb fed back into the "fuel in" supply to the fuel pump with a "one way" valve in? would that do the trick Baz-r ?

thanks
andy :)

[AshG]

got binned mine runs fine without it. put a mini filter up by the carb the nature of them means they never fully fill up so theoretically it will give you a bit of expansion. the pump shouldn't really pump more fuel than the engine can use as they work with the rpm of the engine.

from what i understood the vapour separators were only used to eek that extra bit of fuel economy.

[HandyAndy]

cheers Ash, i like the comment on the fuel economy, i,d heard that before too.

cheers for all your suggestions guys.

cheers
andy:)

[alga]

I thought it's not about saving drops of fuel, it's about minimising hidrocarbon emissions to the atmosphere.

[baz-r]

so, a return from the carb fed back into the "fuel in" supply to the fuel pump with a "one way" valve in? would that do the trick Baz-r ?

thanks
andy :)

the problem with this is when you run dry it may not lift fuel from the tank pumping air round and round in the loop you have made
otherwise all cars would be like it
a rerturn line is the only answer realy and would be handy if you ever wanted to switch to efi setup as you would have a return already fitted

in a standerd carb the inlet port for fuel has a smaller pipe tee'd off so any extra fuel pumped returns back to tank.
your only looking to feed fuel into the float chamber where it will be used at atmosperic pressure (unless your using turbo blow trough eg. metro)
so we dont need that much pressure at all realy

the ford item is designed so just fuel free of bubbles is fed to the carb and the tee off was ommited from the carb as the return was fitted to the seperator on the inner wing

[HandyAndy]

:o hmmmmm decisions decisions .

eventually i,ll be fitting a zetec on bike carbs & megajolt so wouldn,t need efi or a return to the tank.
i,m trying to get the car finished asap,
i,ll try the method as mentioned & if i find its not the way forward i can always reinstall the vapour seperator.

thanks for all your help guys. :cool:

cheers
andy

[twinturbo]

One thing to remember.

Ford, and other manufacturers are tight on the purse strings. If there was no reason for them to fit it they would have left it off. IF you fit the return you can also upgrade the trap to a "Filter King" regulator filter in the future for easy preasure trimming and filter replacement.

TT

[baz-r]

:o hmmmmm decisions decisions .

eventually i,ll be fitting a zetec on bike carbs & megajolt so wouldn,t need efi or a return to the tank.
i,m trying to get the car finished asap,
i,ll try the method as mentioned & if i find its not the way forward i can always reinstall the vapour seperator.

thanks for all your help guys. :cool:

cheers
andy

er? but the seperator would need a return line?

you cuold just pipe up direct but put in the return line later if you where pushed for time .

an idea im sure if the ford unit is to bulky for you vauxhall fitted a plastic version fitted to 8v astra's running 2e3 carbs
its mounted next to the carb on the inlet manifold

[Bonzo]

For what it's worth Andy

Personally I would just plumb up the fuel system without the vapour sepperator, I am sure the fuel pump will be more than able to regulate the fuel suply on its own.

As Ash pointed out, the inline filters will tend to sort out any vapour issues :)

From a study of my redundant, 1.8 CVH carb ( No fuel return outlet ) & a study of the ford fuel layout. The vapour sepperator is for stricter EEC emission compliance. ( Ducks for cover :D )

Penty of CVH engined cars not using a return out there mate ;)

[baz-r]

other idea
blank out the mech pump and fit a eletric pump with a regulator if needed
you would need to go down this route if you go for bike carbs any way

you got me thinking so i read back trough some of my uni books and older car pumps i.e. pre 75 era used a spring to keep the arm one the cam and a linkage that had lost movement (elongated hole) so the diaphram could remain in positon under pressure until the cam came back around.

later on a return line was used and fuel pumps changed

3-5 psi should be about right

somthing like one of thease
http://www.rallydesign.co.uk/index.php?cPath=281_282

and one of thease
http://www.rallydesign.co.uk/index.php?cPath=281_283

[HandyAndy]

other idea
blank out the mech pump and fit a eletric pump with a regulator if needed
you would need to go down this route if you go for bike carbs any way

you got me thinking so i read back trough some of my uni books and older car pumps i.e. pre 75 era used a spring to keep the arm one the cam and a linkage that had lost movement (elongated hole) so the diaphram could remain in positon under pressure until the cam came back around.

later on a return line was used and fuel pumps changed

3-5 psi should be about right

somthing like one of thease
http://www.rallydesign.co.uk/index.php?cPath=281_282

and one of thease
http://www.rallydesign.co.uk/index.php?cPath=281_283

Cheers Baz-r,

now this idea i like :cool:
as would all be ready for when i put the bike carbs/megajolt on, hmmm now i best get looking at those links in detail.:eek: :)

thanks for this info.

cheers
andy