Gas under intake (carb)

hello friends…does anyone one know why under intake next to the carbs…i see a fuel drip by little two valve (respiratory or i dont know ecxactly)…when i turn the key i listen the pump but dont stop and see the bubbles in the glass bowl…

if someone can help me …in advance thanks

If your pump doesn’t stop, it’s likely your float needle(s) aren’t shutting off the needle valve(s) which allows the floats to overfill and the leak from the main jet into the carb throat, filling up the intake plenum before it leaks out the bottom. Give your float bowls a tap with a spanner or similar while the pump is running and see if it stops; sometimes that’s all that is required. Otherwise you will need to remove the float chamber lids and clean the needle valve and check the float height. Not terribly difficult. Also make sure the floats actually float, sometimes they leak, fill up with fuel and sink to the bottom.

Maybe you are talking about 2 little pipes atach to float chamber?? Nope for this pipe not drip…im talkin about 2 litlle purger valve (idont know call it)…below intake …let share the image …

Here are the fuel drip on both little purger…(jaguar mk2…1967…3.4))…

Thanks for you faster answer👍

No, I’m talking about little pipes at the bottom of the plenum, ( curved, polished alloy bit that joins the air cleaner to the carbs), they look ( or should) look like little grease zirks, but curved. One either side, but the things you are showing either aren’t what I’m talking about, or aren’t original. I imagine they probably originally had small drain hoses attached. Sorry, can’t find a picture, but looks to be the same thing you are showing, so my original comments still apply.

Ok…you are right👍…exactly (look like little greasers)…whats is the reason the fuel drip here??
And the solutions??


If you remove the air plenum chamber, ( 2 bolts and 2 dowels, I think, or 4 bolts ) and look through the carb throats, you will probably see fuel seeping up through the brass main jet (s) and if the car has a slight lean to the right,that fuel will drip into the plenum and then out those little drains. Normally, the fuel level shouldn’t be high enough to come out the jet(s), if so, either the float level(s) is set wrong, or the needle valves are not closing and shutting off the fuel, hence the pump continuing to run and cause fuel to overflow. If you remove the carb dashpots and pistons, turn on the ignition, you will easily see if the fuel level rises that far and starts to overflow. You will also easily see whether it is one carb or both at fault.

One question…if the gas overflows through the carbs…it shouldn’t also come out through the small pipes that are on the carbs’ covers and fall towards the ground…then why is gas only coming out through these small drains or zirks…or can be both…

The drains on the plenum are lower than the float chamber ones, albeit maybe only slightly, I think. To flow out of them, float chamber ones, that is, the fuel level needs to rise above the level of the gasket at the top and I think a slow leak would drip out the main jet, but a catastophic failure of the needle valve would result in it coming out the float chamber overflow pipe., because the fuel would be coming in faster than it could drain out the main jet. Could be corrected on that, however.

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I would first remove the SU bells and pistons, (10min) and you will then be looking down at the Jet wells

With the ignition on, they should not be flowing petrol out

If all is well with floats, needles and seats, the fuel level will stabilise about 1/16" below the jet top

Let me try …and see the results…
Thanks for your help…