Carburettor Fuel leak
Turbo Mini Forums

Hi guys, I'm after any advice on this one, I'm a vehicle tech with 33 years experience so not daft when it comes to engines but this friggin car is the bane of my life! I've had a bogging issue for years and I've tried literally everything to find the problem, it turned out to be the choke O rings but now I can't stop the float needle from leaking, I've replace it twice and it still leaks, I've got a fuel pressure guage coming to eliminate the pressure regulator but you can stop the fuel with mild finger pressure. Anyone else have this persistent problem?

Sounds like excessive fuel pressure.

Once you have your gauge, check that it’s around 3-4psi.

In the 13's at last!.. Just

So by your description it sounds like you have fuel coming up the main jet and flowing into the intake manifold I would check the float needle valve is clean and in good condition. if your fuel pressure regulator was not returning you would have fuel everywhere for as you are well aware the injection type fuel pumps used in these systems can hit 9 bar.

Own the day

As Josh says, the needle cannot leak persay...it is always a leak.

If fuel is flowing out it uncontrollably, then it is most likely the needle valve not sealing in the float chamber. This has nothing to do with the main fuel metering needle.

pretty decent rebuild video

https://www.youtube.com/watch?v=e15QlVLjJiU

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I've replaced the needle valve twice! The pressure gauge as just landed so I will see how that goes.

I've replaced the needle valve twice! The pressure gauge as just landed so I will see how that goes.

have you made any adjustment to the paddle on the float. it could be that the needle valve isn't being closed by the float. its happened in the past

Own the day

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I've tested the fuel pressure and its 6psi

On idle its 7.5 but won't come down

Either the reg is broken, or your return line is restricted.
Try putting a length of hose straight off the return outlet on the reg into a suitable container and see if the fuel pressure will lower then. If that’s successful, make sure the return is big enough, and non of the rubber hoses have kinked or collapsed.

Phil.

WWW.TURBO-MINI.COM

I've got some success!
Straight out of the regulator it can go down to 3psi so that's fine, the return was kinked in the boot so I straitened it out and put the container in the boot, it still adds 1.5 psi and the tank adds another 1.5 psi totaling 6psi when running, the only other thing is I fitted 8mm flow and return! I'm thinking of putting a 6mm piece of pipe to restrict the flow and give it another try. It's getting better as it's not pissing fuel out anymore.

larger return. Fix it so it can flow.

trying to restrict pump flow isn't a great option, although probably doable.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

If you've got an 8mm return then there's something wrong with it, you shouldn't get a 1.5 psi pressure drop with it and you also shouldn't get another 1.5 psi feeding into your tank. Has the pipe been crushed anywhere under the car? Are you using full bore fittings on it or fittings with a tiny hole? Any 90 degree fittings anywhere possibly?

Edited by neilj1678 on 28th Mar, 2023.

Sorry to keep going on but my fuel lines are both 8mm od and I'm guessing 6mm id!
I've measured the tank return on the tank itself and its 5.3mm id so I don't see how a 8mm id would benefit as the tank is a bottleneck!

The return to the tank needs to be able to scavenge more fuel than the pump can supply thats why it needs to be of a greater bore your return line is way too small! you need 3/8" return.

Edited by Mr Joshua on 29th Mar, 2023.

Own the day

deleted

Edited by Mr Joshua on 29th Mar, 2023.

Own the day

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I fitted the pipe sizes from the metro turbo fuel tank in the end. That meant fitting the tank with two 3/8" pipes for feed and return after that I didn't need to run the resistor on the fuel pump as there was no longer the restriction caused by the tank outlet. I wanted to fit the swirl pot but just ended up fitting the strainer. It may not be what you wanted to here but my issue plagued me for over a year. When all else failed, I binned all of my fuel system broke another metro turbo and fitted everything like for like. That's when I became aware of the restriction. Your issue is its causing a fuel leak mine was fuel starvation at the pump, yours is the return line mine was the feed line.

Own the day

I've now got it down to 4.5psi as the pipe in the boot had been squashed flat. After 10 years I've finally go the friggin thing running smooth, one of the fixes was the seals in the choke spool.

1293 Turbo mini