Carburetor adjustment doing nothing

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12jslater
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Carburetor adjustment doing nothing

Postby 12jslater » Fri Jul 05, 2019 2:09 am

I'm 17 and recently purchased a 1956 car still sporting it's original paint, I have spent the last few weeks getting the old girl back up to running order after sitting since the mid eighties.

However she's running rich! Adjusting the carburetor seems to do nothing and in traffic she either stalls and won't restart until left to sit for a few minutes or absolutely stinks to high heaven of petrol and runs like a three legged dog.

Does anyone know what this may be?

Thanks!! 🙂

don58van
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Re: Carburetor adjustment doing nothing

Postby don58van » Fri Jul 05, 2019 3:21 am

Possibly the needle valve in the carb is stuck open, thus overfilling the float chamber. This would cause constant very rich running.
Good luck sorting it out.
Don

oliver90owner
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Re: Carburetor adjustment doing nothing

Postby oliver90owner » Fri Jul 05, 2019 6:33 am

As Don, but not stuck fully open. Could be something in the valve, valve slowly leaking due to age/wear or fuel leaking in around the threads of the connector. Alternatively it could be that the float chamber level, is set wrong or a gasket (for example) is preventing the float movement. While vehicle is stationary. Unlikely , but could even be the fuel pump delivering too much pressure.

Suffered from all these faults, over the years, on vintage machinery. Usually an easy fix - once diagnosed.

pgp001
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Re: Carburetor adjustment doing nothing

Postby pgp001 » Fri Jul 05, 2019 8:31 am

I once had a problem with the main jet having a split down one side and letting too much fuel in. But as others have said check the float and needle etc first.

Phil

simmitc
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Re: Carburetor adjustment doing nothing

Postby simmitc » Fri Jul 05, 2019 10:07 am

Welcome, sounds like a good find, and well done for getting back on the road so quickly. If not already done, I'd strongly advice having an MOT done just to make sure that everything is as it should be.

As regards the carb, could you post a photo of it please - we know that it "should" be, but after so many years, it could have been chnaged by a previos owner. Does the jet move down when you pull the choke out, and return up when the choke is opushed in? Is the jet sitting firmly against the adjuster nut?. Is the needle rising and falling freely?

Smell of petrol - is the pipe leaking, particualrly the flexible one? Rough running - is it firing on all four cylinders? Is the fuel pump working OK - measure the quantity of fuel delivered over a period of one minute. Has the pump been serviced, clean filterm good diaphragm and valves?

Does the car start and run OK when it's cold? In all probability, you're looking at one fault, but it could be two separate problems.

12jslater
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Re: Carburetor adjustment doing nothing

Postby 12jslater » Fri Jul 05, 2019 10:47 am

I did replace the fuel lines, the fuel pump has been completely rebuilt and carburetor gaskets been replaced, I had checked the valve less than a week ago when the carb was off the car and it seemed to worked absolutely perfectly.

And I did drive the old girl for an hour long journey on Saturday, to Bridgnorth and while moving she's driving fine, she made it there with no complaint yet as soon as I stopped the car in the town itself it died and I had to wait a good few minutes before it would start back up. it's only when the engine is warm and in slow moving traffic/idling

Thank you

philthehill
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Re: Carburetor adjustment doing nothing

Postby philthehill » Fri Jul 05, 2019 3:11 pm

It sound as if you are experiencing overheating of the mixture in the fuel pipe, carb & manifold leading to excessive vaporisation of the fuel (vapour lock) before it reaches the cylinder. A common fault with this weather and not only with Minors - the Ford Cortina I had was terrible in warm weather and would not start but left 20 min it would fire up easily.

https://en.wikipedia.org/wiki/Vapor_lock

You can get a kit to keep the heat away from the float chamber and fuel delivery pipe, originally made by Grumpy's.
img133.jpg
img133.jpg (400.25 KiB) Viewed 298 times
Now available from ESM

https://www.morrisminorspares.com/fuel- ... ly-p830677


mowogg
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Re: Carburetor adjustment doing nothing

Postby mowogg » Sat Jul 06, 2019 11:09 am

If the adjustment is not doing anything it could be wear to the needle or jet. These do wear and changing them can result in dramatic improvements. I think I would start here if you don't know the history of the jet and needle


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