Morris Minor Owners Club

Hi new to classic cars so be gentle.
I am having issues with my mother's 1954 moggie with the 1098cc engine fitted, I can get it started and drive it around and it has plenty of power, however at idle it slows down and cuts out.
Fuel pump is working, float bowl full when it cuts out. Will stay running if idle set really high but obviously not ok, my 1967 runs at a much lower idle speed.
Please help before I put a match to it

Has the car been left sitting for a long time?
It could be any number of things, but a good service may sort it out.
I would start by checking whether there is enough oil in the carb damper. Lack of dashpot oil will cause a car to stall at idle.
If that is OK, I would clean out the dashpot, make sure the piston is moving freely, needle fitted correctly and check the fuel mixture.
Then, if no improvement, go through the ignition system - are the plugs and points clean/set properly?

As well as the suggested checks, Is the choke stuck on, so needs higher rpm/more air due to richness?

Little update, I have had the carb out and put back together, needle and jet lined up and piston moves freely and returns with a nice clunk. I left it for a while and it started straight up and only started to have issues as it got hotter. Im thinking potential vapour lock and am wondering if I have damaged the spacer between the carb and the manifold allowing the exhaust to overheat the carb (I have just done the head gasket)

Could there be an air leak in manifold?

It could, indeed, be an air leak at the manifold, seeing as the HG has just been done. Alternately, were the valve clearances set correctly after the HG job?
Has this problem only manifested after doing the HG? I assume dashpot was correctly filled with oil after its overhaul?

Tappets set at 15thou when I did the head and cleaned all the faces and fitted new gaskets on the manifold. The car was bought as a non starter so cannot say whether this problem was there before. It starts reliably when cold and will run for a good while then just splutters and dies. Dashpot oil is all good and carb piston moves freely, fuel pump contacts cleaned, new plugs and coil. Only seems to happen when hot

I can't see how you could have damaged the spacer between the carb and the manifold without it being obvious. From what you now say, I am wondering if it is a failing condensor or coil (despite it being a new one - some modern coils are very poor quality. If you have the old one, I would swap it back in).

I only changed the coil today to try and fix the issue, its electronic ignition so no condenser I'm a bit lost. Going to make a heat shield at work on Monday to try and rule out vapour lock but if not back to the drawing board

My initial thought, after the usual oil in the carb dash pot, was float level setting. Leaking manifold gaskets are a possibility - the inlet and outlet ports may not be flat, but a check on the plugs ought to give an indication if there is a leak? Before now, I have used an extra gasket under a non-aligned manifold to get over that problem.

With the float level does it want to be lower or higher do you think? I have a new manifold gasket so will check all that in the morning.
Really appreciate all your help, I am a diesel mechanic and all this petrol stuff is new to me

Take a spark plug out and look at the electrode colour. If it is a leak on the induction side the mixture will be weak and the plug will look pale. I had such a leak a while back and the engine would only stay running with the idle set high and the choke out.

Stephen

Did it come fitted with electronic ignition or have you fitted it? It could be breaking down when hot.
Maybe worth fitting a set of points and condenser to try.
Useful to carry as spare back up even if not solving the issue.

It came with it on, I did think about converting it back

Good news I found the problem, I went back and looked at the one bit of the carb I didn't mess with and found the needle fitted incorrectly, it was recessed a good 5mm causing a fair bit of over fuelling choking the car out. Thank you all for your replies

Surely if it was running so rich it was belching black smoke? A look at the spark plugs would have quickly identified this too.

Glad it's fixed.


Stephen

This was my first time working on a petrol car let alone a 70 year old one, I don't think I did too badly
All experience in the end and really enjoyed it. There was no smoke at all which surprised me too, but she is running sweet now

Question now arises as to why the carb had been assembled incorrectly. Back to float level?