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stewartp
 Post subject: Carburettor problem
PostPosted: Thu Jul 31, 2025 9:27 pm 
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Hi, I'm having problems getting my S running properly, initially I had manifold leaks but now fixed

Taking the dashpots of and looking at the seats the passenger side, or radiator side, looking from the front of the engine bay, is wet with fuel, the drivers side is dry.

Any suggestions on what could be causing this, and a remedy.

Thanks Stewart

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drmini in aust
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 8:16 am 
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I would check that the float levels are the same first. Assuming that one isn't flooding through its overflow.

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stewartp
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 8:55 am 
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Location: Mt. Barker sa
Thanks for the reply that's been checked and ok.
Even replaced the float bowl too with a different one.

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Last edited by stewartp on Fri Aug 01, 2025 12:08 pm, edited 2 times in total.

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Steam
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 9:57 am 
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The problem would seem to be that fuel is not getting to the jet correctly. As said above the fuel level is set by the float chamber so of this is correct and the levels are the same in each float chamber then I would suggest the pipe from the chamber to the carb has an issue. The o ring that seals in the base of the chamber can block the flow of fuel or the pipe itself can become twisted an distorted causing a fuel blockage.
Try putting a straw or pipe over the jet at the offending carb and blow in to the jet, you should hear or see the air being blown into the float chamber. There may also be debris in the chamber or pipe stopping the flow of fuel.

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68+86auto
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 10:05 am 
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What part are you saying is wet?


Can you post a current photo of the carbs fitted to the engine?

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stewartp
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 12:20 pm 
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Location: Mt. Barker sa
The jets are brand new, when the issue has only just occurred,the carbs have been cleaned with new new parts fitted,
fuel filter in the line and no debris in the bowl.
I can see the level drop if I wriggle the linkages.
I'm at the point of replacing the carbs with a spare set, but prefer to fix the problem.
68+86auto The fuel is sitting on the top of the seat where the needle fits into the jet. They are standard HS2

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68+86auto
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 2:36 pm 
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stewartp wrote:
The fuel is sitting on the top of the seat where the needle fits into the jet. They are standard HS2


The fuel should be below that surface.

It is probably one of the following:
- Jet adjusted way too low (rich).
- float valve defective
- float level incorrect
- float defective (leaks or pivot hole worn)
- fuel pump pressure high

One simple check is to hold the lid upside down and blow into the fuel fitting and check that it shuts off.

The picture is to make sure they are connected correctly. I've seen topics go for pages until a picture was posted which revealed a disconnected hose.

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lomin
 Post subject: Re: Carburettor problem
PostPosted: Fri Aug 01, 2025 6:12 pm 
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Hi, its not unknown for the old jet tube o ring to remain in the float bowl when replacing jets….. that would be a restriction
cheers Lindsay

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stewartp
 Post subject: Re: Carburettor problem
PostPosted: Sat Aug 02, 2025 9:22 pm 
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Location: Mt. Barker sa
Thanks for suggestions, haven't time at the moment to follow up, I'll update when I get back to it.

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If you could erase all your mistakes of the past
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Remember the lesson not the disappointment.
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Bill B
 Post subject: Re: Carburettor problem
PostPosted: Sun Aug 03, 2025 6:23 pm 
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Steam wrote:
The problem would seem to be that fuel is not getting to the jet correctly. As said above the fuel level is set by the float chamber so of this is correct and the levels are the same in each float chamber then I would suggest the pipe from the chamber to the carb has an issue. The o ring that seals in the base of the chamber can block the flow of fuel or the pipe itself can become twisted an distorted causing a fuel blockage......


I might be getting the wrong idea here, but the problem doesn't sound like a fuel blockage. It's uncontrolled fuel level spilling out of the jet, suggesting the fuel bowl needle and seat are not shutting off when the front carb's fuel bowl is full.

When you changed the float bowl, did you also fit another needle and seat? If not, could there be a small piece of debris getting caught in it?

As a wild thought, could the float bowls for each carb be at different levels - as in different bowls for different applications?
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68+86auto
 Post subject: Re: Carburettor problem
PostPosted: Sun Aug 03, 2025 7:20 pm 
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Bill B wrote:
I might be getting the wrong idea here, but the problem doesn't sound like a fuel blockage. It's uncontrolled fuel level spilling out of the jet, suggesting the fuel bowl needle and seat are not shutting off when the front carb's fuel bowl is full.


That's what I understand too, I keep wondering what I'm missing since everyone else is talking about a restriction (the opposite). It's good that it's not just me.

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Oscar
 Post subject: Re: Carburettor problem
PostPosted: Mon Aug 04, 2025 11:04 am 
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Yeah I'm with you guys too. Flooding from the jets is certainly not for lack of fuel...

Several years ago I was prepping our car for a roadworthy to transfer to club permit and gave the little bugger a real good birthday.
One of the many tasks I did was an overhaul of the twin SU's, including replacing the needle/seat and jet assemblies.

Strangely, on startup both bowls flooded from the bowl breathers!!! I played with the float levels until it stopped, however the best I could get still had fuel flooding from the tops of the jets...
I bought a couple more new needle/seats thinking I had a couple of dodgeys - exactly the same - had to be a pressure issue then...

I thought back to the 80's when the original SU electric pump died on me as I drove into the car park for nightshift at work.
I pushed it into a space and went out with some tools later on and removed it. I took it into my workshop and opened it up to find it was beyond salvation...
A mate drove me home the next morning, on the way stopping into my goto place for parts, where I bought the cube pump they had listed for the mini.
I installed it that night in absolutely pouring bloody rain and the little beast was back!

The car had run happily on this pump for the next several decades until now... Bloody weird!
I got the model number from the pump and looked up the specs - 3-4.5 PSI, 30 GPH - shouldn't be an issue but to hell with it - I bought the next pump down - 2-3.5 PSI, 28 GPH.

EUREKA!!! Flooding stopped and with a reset of the float levels all was sorted!

It seems the needle/seats, like everything else for these little beasties, just aren't made like they used to be...

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stewartp
 Post subject: Re: Carburettor problem
PostPosted: Mon Aug 04, 2025 12:02 pm 
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Joined: Wed Apr 09, 2014 8:20 pm
Posts: 127
Location: Mt. Barker sa
Oscar wrote:
Yeah I'm with you guys t
from the jets is certainly not for lack of fuel...

Hi, thanks I am using an ecco pump made in NZ which has been working fine.

Several years ago I was prepping our car for a roadworthy to transfer to club permit and gave the little bugger a real good birthday.
One of the many tasks I did was an overhaul of the twin SU's, including replacing the needle/seat and jet assemblies.

Strangely, on startup both bowls flooded from the bowl breathers!!! I played with the float levels until it stopped, however the best I could get still had fuel flooding from the tops of the jets...
I bought a couple more new needle/seats thinking I had a couple of dodgeys - exactly the same - had to be a pressure issue then...

I thought back to the 80's when the original SU electric pump died on me as I drove into the car park for nightshift at work.
I pushed it into a space and went out with some tools later on and removed it. I took it into my workshop and opened it up to find it was beyond salvation...
A mate drove me home the next morning, on the way stopping into my goto place for parts, where I bought the cube pump they had listed for the mini.
I installed it that night in absolutely pouring bloody rain and the little beast was back!

The car had run happily on this pump for the next several decades until now... Bloody weird!
I got the model number from the pump and looked up the specs - 3-4.5 PSI, 30 GPH - shouldn't be an issue but to hell with it - I bought the next pump down - 2-3.5 PSI, 28 GPH.

EUREKA!!! Flooding stopped and with a reset of the float levels all was sorted!

It seems the needle/seats, like everything else for these little beasties, just aren't made like they used to be...

_________________
Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.
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