Classic cars forum & vehicle restoration.

[Miken]

Any thoughts on the following please;
I have recently aquired a 1927 Morris Cowley with Magneto ignition.
I have been happily driving it around these last few weeks and dont want to stop.
Today I went out for a christmas eve drive. Its a bit damp but ive been out in worse. After about a mile it started misfiring,loosing power and smoking badly. After a bit of fiddling I managed to limp home by putting the choke partly on.
It conked out completely as I arrived home.
I have tried the followoing.
Stripped and reassembled the SU carb and found a lot of sludge in the float bowl and strainer ( I thought that would be it). The fuel is flowing from the gravity fed scuttle tank nicely. It only has to travel about 12" down to the carb. Checked the ignition timing with a dial gauge down the hole provided in the cylinder head for this purpose. Spot on.
Pulled the HT leads off and I have a nice blue spark when the engine is turned over. attached a spark plug to the leads and still get a nice spark.
If I really tickle the carb and flood the float bowl, it will run for a few seconds before dying.
During that time clouds of blue smoke come out the exhaust.
Oil level,is half way between High and low on the stick
Why is it suddenly smoking so badly? It was fine yesterday.
Thanks
Mike

[Rich5ltr]

Hesitate to say but could it be mechanical? Something like a sticking valve or a broken piston ring? The smoke suggests oil to me, have you done a compression test?

[kevin2306]

Best to go back to basics, check compression, check sparks, check fuel system etc.
With winter here it is a good time to give the old girl a good looking at, if there is any time left then spend it on the car
I would also be getting the mag checked over, if it's breaking down under load it will throw up all sorts of symptoms.
Good luck with the fault finding

Kev

[peter scott]

Hi Mike,

It sounds like your ignition is OK.
Try removing the SU dashpot and piston and check that the fuel level is just below the top of the jet.

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[Miken]

Thanks for the helpful replies.
I have done a compression test and achieved the following readings in Bar's with dry cylinders.
No.1 to4 cyl read 5.2, 4, 5, & 5.5.
Clearly no2 is down a bit, but not hugely? Its definitely compressing.
I then squirted some oil into each cylinder . Bearing in mind this is a SV engine and the spark plug holes are above the inlet valve (or exhaust im not sure) I tried to get the oil over the pison to seal the rings and achieved 6, 5, 5.5 and 5.7 respectively. But this might have just sealed up the valves too.
I had a peek in the valve chest and all the valves are going up and down and no springs are broken.
Ive got to go and play Cristmas now , Bah! Humbug!
I will try Peters suggestion next. But probably not today or tomorrow.
Peter,
If I lift off the dashpot and piston as you suggest, How do I see if the fuel level is just below the jet?
Do I lower the jet with the choke and look for fuel overflowing the top?
Thanks MN

[Miken]

Ive spent all day trying to get my car to start.
Swapped mag (again)
Carb off and dissasembled and rebuilt (again)
Checked compression (again)
New ht leads.
In desperation (and I dont know what made me do it) I unscrewed the brass cap at the top of the dash pot and poked my little finger down and pressed onto the top of the weighted piston therein.
I was then immediately able to start the engine. As long as I hold the piston down with my finger it runs (but wont increase revs without cutting out). If I remove my finger and screw on the cap it stops.
In the meantime it is issuing huge clouds of grey smoke from the exhaust. Ive never seen anything like it. The smoke takes several minutes to clear from my garage.

[alanb]

By pressing the piston down you are effectively weakening the mixture, when the engine is running the piston rises when you accelerate withdrawing the needle from the valve allowing more fuel to flow. When operating the choke you pull the jet down thus allowing more fuel to flow. Are you sure the needle is seated correctly in the jet? is the piston free and lubricated? Is the jet returning fully and not being held in the choke position?. If as you say by holding the piston down it runs it sounds to me as though it's set far to rich.
_________________
old tourer


Morris 8 two seater

[Miken]

Thank you for the helpful replies.
I have decided to stop fannying around and have a proper look inside the engine. Im glad I did because i dont think the clutch would have held out much longer.
See the following account of the engine rebuild that will follow here:-
http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?p=147436#147436

[jp928]

When you push the damper into the SU top housing , do you feel resistance from the oil in there? Are there signs of wear on the needle from rubbing on the jet? If so, redo the centering.
Usual test for SU float bowl level (late ones with fuel going in the top) was remove the bowl cap, turn upside down - this should shut the needle/seat - you should be able to get a 7/16" rod between the edge of the cap casting and the lever that the float pushes on to shut the needle.
Needle and seat dont last forever, especially those with brass tips - the later rubber tips last better.

jp 26 Rover 9