31 replies to this topic

[HUBBA.HUBBA]

Been on the rolling road yesterday for a fueling issue. Transpires that when the fuel pump is switched on the fuel just fountains out of the jet about a foot high! ( dash pot and piston taken off). The carb was rebuilt prior to me purchasing it with the full proper rebuild kit inc vitton tipped float chamber valve. I've had a look at the float set up and there are not obvious signs of any particles keeping the valve open So my question is why the hell is the fuel passing. It is on 3 psi.

[Icey]

Does the valve actually seal? If you fill it 'manually' (funnel and a length of hose) does it still leak?

[HUBBA.HUBBA]

Does the valve actually seal? If you fill it 'manually' (funnel and a length of hose) does it still leak?

I'll give that a go. Was thinking of physically holding the valve in place an switching on the pump, but your idea seems more sensible. Cheers

[HUBBA.HUBBA]

Did that and it still passes. Tried adjusting the float level with 0.5mm gap using a straight edge using the weight of the float and no joy. It either wont pass at all or just flows through. No happy medium. The spring is strong in the vitton needle. Holding the needle in whilst funneling some fuel in and it seals. Transfered the the whole valve, float assembly into another carb (non turbo hif44) and it seals fine!
I wonder if you can get play in the float where it attaches to the brass tab?

Edited by HUBBA.HUBBA, 25 September 2016 - 02:48 PM.

[Icey]

That is odd. I'll have a look at the 44 I have on the shelf and have a think.

[Ethel]

Yes, the float pivot can wear. Are you sure the pressure regulator is only passing 3psi? Did you measure it in situ with the pump running? - I'm wondering if a restriction on the return to the tank is keeping it from closing.

[HUBBA.HUBBA]

Yes, the float pivot can wear. Are you sure the pressure regulator is only passing 3psi? Did you measure it in situ with the pump running? - I'm wondering if a restriction on the return to the tank is keeping it from closing.

The fuel pressure when the pump is switched on goes to 3psi. When it/if the engine starts momentarily. Shoots up to about 12 psi when on boost and drops back when off.

[HUBBA.HUBBA]

That is odd. I'll have a look at the 44 I have on the shelf and have a think.

ok cheers

[burchy35]

I had this exact problem with my turbo. I must of taken my carb off 20 times, I must of smelt like I had been swimming in petrol.
But anyway the problem was that the spigot that is next to the fuel intake on the carb had been knocked in to far and was blocking the balance pipe that runs from the float chamber up to the small hole at the back of the carb which meets the plenum. Fuel was being forced into the float chamber as it should but the air had know where to go so it just pressurized the chamber which forced the fuel out of the jet. I simply used some small grips and pull the spigot out about 5mm and its all good now.
It's worth checking if nothing else.

Roy B

[HUBBA.HUBBA]

I had this exact problem with my turbo. I must of taken my carb off 20 times, I must of smelt like I had been swimming in petrol.
But anyway the problem was that the spigot that is next to the fuel intake on the carb had been knocked in to far and was blocking the balance pipe that runs from the float chamber up to the small hole at the back of the carb which meets the plenum. Fuel was being forced into the float chamber as it should but the air had know where to go so it just pressurized the chamber which forced the fuel out of the jet. I simply used some small grips and pull the spigot out about 5mm and its all good now.
It's worth checking if nothing else.

Roy B

That's really interesting, cause I did a check with pump on and keeping my thumb on the jet and I could see bubbles through the pool of fuel coming up from a small hole just after the jet before the throttle (one of two).  Could that be the same thing?

[Ethel]

The small hole is the choke jet.

[HUBBA.HUBBA]

The small hole is the choke jet.

What's the other one next to it?

[HUBBA.HUBBA]

[attachment=185351:20160928_130705.jpg]
[attachment=185352:20160928_130734.jpg]
The bubbles came out of the hole the one with the screwdriver pointing at it

[HUBBA.HUBBA]

Birchy35- is this the sprocket you are talking about, the one with bung on it next to the fuel supply?

[attachment=185353:20160928_130812.jpg]

[Ethel]

Not seen this on a Metty or Mini that I recall, but s'pose it's an option?