The Triumph Dolomite Club - Discussion Forum

had issues last lime my dolly was running, if it was sat still, say in traffic, the carbs would leak petrol out of the float bowls, either onto the inner wing or onto the hot exhaust

is this a common fault?

can it be fixed or should I just put a return system in to send that fuel back to the tank.

If they are SU's and they probably are, easy fix. You have a sticking needle valve in the float bowl, I think. Take the lid off the bowl, and remove float, drive out the pin.

The needle valve will drop out, clean it with some solvent, put it back. If that doesn't fix it, new valves are cheap.

I would also recommend that you blow through the top of the carb that you have removed to ensure that you get any bits out that might have been causing the needle valve not to seat properly. I have found that the most common problem is when you have detached and then replaced the rubber hoses that connect the petrol pipes as it is easy to slice off a small piece of rubber from the inside of the rubber pipe as you put it back together. This then flows with the petrol and get caught up in the needle valve.

I would also recommend that you have a replacement gasket available for the carb top to body before you start as the original may give up when you remove the top.

I've had the same with the addition of an incorrect float lid gasket, (too thick)
and old rubber pipes joints under the car, which kept shedding bits,
and getting stuck in the fload lid valve.

cleverusername wrote:If they are SU's and they probably are, easy fix. You have a sticking needle valve in the float bowl, I think. Take the lid off the bowl, and remove float, drive out the pin.

The needle valve will drop out, clean it with some solvent, put it back. If that doesn't fix it, new valves are cheap.

I did that the first time they leaked, I then replaced them with Ball valves which were worse. I had cleaned them and had a fuel filter installed, it still leaked

Forgot to add, when you take out the float pin, then the float, then the needle, unscrew the brass (nut) seat, mine had a
bit of rubber pipe in there which would not shift unless unscrewed.

The other problem you may have is that some replacement fuel pumps have been found to deliver too high a pressure which then overwhelms the needle valves. Pressure from the pump SHOULD be in the region of 2psi, some aftermarket pumps have been tested at up to 6psi! Cure is to swap the pump for something more OE spec, or fit a PCV between the pump and carbs.
But check for crap in the needle valves first! And holes in the floats!

Steve

Carledo wrote:The other problem you may have is that some replacement fuel pumps have been found to deliver too high a pressure which then overwhelms the needle valves. Pressure from the pump SHOULD be in the region of 2psi, some aftermarket pumps have been tested at up to 6psi! Cure is to swap the pump for something more OE spec, or fit a PCV between the pump and carbs.
But check for crap in the needle valves first! And holes in the floats!

Steve

ok, ill check if its a aftermarket pump.

another thing I just remembered is that as well as the carbs leaking out of the vent holes while driving, once stopped, it will squirt fuel out on the fuel lines leading onto the carbs, usually out of the one closest to the radiator. it was a bit concerning that the car could burn itself down after I have just got out of it.

If my memory's any good, it was a decent amount of fuel that shot out

That does sound like the pressure is high....

But as said check the float valves first.

Jonners