Engine

[Mark.stephenson485]

Engine starts but no throttle response
Just idles
Challenged carb no difference
Has new pcv valve new fuel pump
Doesn't seem to be enough suction to pull fuel In.
Could the valve clearances need checking.

[myoldjalopy]

Is the throttle cable connected/sticky? Try operating the throttle at the carb manually. I can't see its anything to do with valve clearances. Do you mean 'changed carb'? Not sure how one can 'challenge' a carb!

[Mark.stephenson485]

Throttle pedal moves lever on carb but no response.

[svenedin]

Throttle pedal moves lever on carb but no response.

Does the throttle disc move in the carburettor when the throttle lever moves? It is possible for the throttle disc to just spin on its spindle if its securing screw is missing. Remove air filter, lift piston with your finger and look to see if the throttle disc rotates with the throttle lever. Also check that the carburettor piston moves freely and when lifted and let go it should fall with a metallic clunk. It's possible the piston is stuck.

Stephen

[mowogg]

When you press the throttle does it not do anything?

[svenedin]

Apologies. I have missed something in my earlier reply. I should have clocked on because you say in your post "there doesn't seem to be enough suction to pull fuel in". This is because you have an air leak.

The OP asked previously about installing a PCV valve and has now installed one. I have a PCV valve set up which is relatively unknown in the Minor community as they were only used late in production and many have been deleted in favour of a breather carburettor arrangement.

Mark I think you have symptoms of a big air leak on the engine inlet side. The most likely place for this leak is the section of pipe between the inlet manifold and the PCV valve or the spigot that screws into the manifold.

I suggest you take out a spark plug and look at the electrode. If it is a pale anaemic white it means the mixture is way too weak which would confirm my suspicions.

If I am correct, take the PCV valve off and check the spigot is secure in the manifold. I used thread lock on it. Then refit your PCV making sure the pipe is secured with 2x Jubilee clips one tightening round the spigot off the manifold and the other round the stem of the PCV. The vacuum between manifold and PCV is strong and a leak of air into here gives symptoms of a severely weak mixture. You need to use 1/2" inside diameter reinforced hose that is suitable for oils like this (which is actually fuel hose): https://www.somerfordmini.co.uk/breathe ... -per-metre

Also check the hose connections from PCV valve to the tappet cover canister. These must also be secured with Jubilee clips.

Lastly, if you have fitted a second hand PCV valve, check the diaphragm. If it has a hole in it you will also have a severe vacuum leak.

When you have fixed the leak you will need to set the fuel mixture.

For those not familiar with this setup see this page and the diagram labelled "manual gearbox": https://www.somerfordmini.co.uk/catalog ... 774_100817


This is my setup:

IMG_9140.jpeg (1.91 MiB) Viewed 9732 times

Stephen

[oliver90owner]

This is because you have a vacuum leak.

NOOO! An air leak, maybe, but NOT a vacuum leak - a vacuum, by definition is at a lower pressure than the surroundings, so a fluid will always move towards the vacuum space

Perpetuating myths is far too easy.

[Mark.stephenson485]

When you press the throttle does it not do anything?

Does nothing at all.
Take foot off pedal and engine dies.

[svenedin]

When you press the throttle does it not do anything?

Does nothing at all.
Take foot off pedal and engine dies.

Do take out a spark plug and report back the colour of the electrode. As I said in my post I think you will find a white electrode caused by a very weak mixture.

[Mark.stephenson485]

Plugs are black.
No smoke from exhaust.

[svenedin]

Plugs are black.
No smoke from exhaust.

There goes my theory........

Black plugs suggest the mixture is too rich

[philthehill]

Remove the PCV valve, block the rubber pipe to the inlet manifold with a suitable bolt and start the engine and see what happens.

[jaekl]

What is the history of your Minor? Was it working fine last week or has it been sitting? The exhaust could be severely restricted. Loosen the exhaust clamp and see how it runs.

[liammonty]

Plugs are black.
No smoke from exhaust.

You'd do well to answer the question regarding whether the throttle butterfly moves with the actuating lever on the side of the carb

[Mark.stephenson485]

Brand new carburettor
Butterfly moves freely

[Mark.stephenson485]

Brand new carburettor
Butterfly moves freely

[oliver90owner]

Brand new carburettor
Butterfly moves freely

That is not answering the poster’s question. I expect there is no positive connection between pedal movement and carburettor butterfly valve. That is about all I can discern from this thread, thus far.

Engine operation at idle is about as useful as …. i would expect plugs to be black after start-up — cold, likely needed a rich mixture for start, etc. There is, I expect, a simple reason for this ‘apparent’ problem.

[mowogg]

Given that it's a brand new carb has the mixture been adjusted correctly?