leaking carbs

[tr7mgb]

Vitesse mk2

my front stromberg 150 carbs is leaking from the bottom. i have changed the seals 3 times now and the damn things still leaks

any ideas?

[Royboy66]

Float needle valve worn/sticking ?

[Davemate]

Have you fitted a new fuel pump, there are quite a few that are "over fueling".

[Royboy66]

1344 wrote:

Have you fitted a new fuel pump, there are quite a few that are "over fueling".

Yup Agree!  "Been there!"

[Encom]

Same. Ended up using a very low pressure pump Fuelflow 15L, spec's below;

http://www.fuelflow.co.nz/FF_cms_03/eshop?page=shop.product_details&category_id=41&flypage=flypage.tpl&product_id=76

[Davemate]

Or fit a filter king (other brands are available) fuel presure regulator for about £30-50 and never worry again about dodgy over fuelling fuel pumps

[tr7mgb]

I never thought about the fuel pump over supplying

i thought that it must be the seals not sealing fully, would an over zealous fuel supply cause this then? i had assumed that the seals cannot cope with the pressure?

it continues to leak however once the engine is off

what pressure should the pump be supplying?

[junkuser]

I've found that Strombergs handle over-pressure quite well, but if they do leak due to this, the outside of the bowl will be wet as the overflow is from the top.

If the bowl is dry on the outside, but the the jet holder is moist, then an "O" ring problem is the cause.
This will occur with engine not running, as John describes.

[Davemate]

Ask mr Radders,he tried two or three sets of stromy carbs all leaked. He replaced "o" rings and gaskets to no avai.
He fitted an electric pump instant fix !
They will still leak after the engine is turned of ,but only until the pressure drops. If the leak continues for ages then you have other issues or more than one fault !

First thing I would do is pull the fuel supply pipe off the carb and start the engine if fuel shoots across the gararge then it's has too much pressure !

[Encom]

6931 wrote:

I never thought about the fuel pump over supplying

i thought that it must be the seals not sealing fully, would an over zealous fuel supply cause this then? i had assumed that the seals cannot cope with the pressure?

it continues to leak however once the engine is off

what pressure should the pump be supplying?

The Fuelflow 15L supplies a steady 2 to 2.5Psi.

[Pete Lewis]

if its leaking from anywhere around the float chamber it has nothing to do with pump pressure the float bowl is open vented and atmospheric pressure only
  if the float needle  is overriden by pump pressure then it will escape from the vent port in the outer face

any leaks from elsewhere are down to distorted jet holder,  ( seen some real mullered ones) undersize O rings or you have fitted an incorrect float chamber gasket
there are many variations thro the life of these carbs and whilst they look ok you will find a cd , cds, cdse all are marginally different and if you follow the  sealing line of the chamber there will be a small section that is left  'open'
  and there is a perpetual leak ,  It may be a new gasket but wrong generaion... catches  a lot of guy's out .

Pete

[junkuser]

"or you have fitted an incorrect float chamber gasket"
    The float bowl gasket is above the vent and correct fuel level Pete so, if fuel level correctly set and needle valve controlling the flow, petrol should not be able to leak from the gasket unless you are doing some pretty wild driving.

As you say, damage on any surfaces the 3 "O" rings seal on can cause leaks at the bottom, including the bore in the float bowl.

An off-centre jet or distorted float bowl could also make it harder for the "O" rings to seal, but I feel John would have noticed such things as he seems to be thorough in what he does.