Technical Cutting out

[Kiltedboarder]

Hi all
So went for a longer drive today, all going well. Then on the return journey came to a roundabout, slowed down, got a bit of a misfire and then a drop in power and a very hesitant engine. It picked up and on I drove. Then just when I got to the house as I slowed to enter my garage, revs dropped off, very hesitant engine, lots of fluffing and puffing from the engine. No matter of using the throttle would make the engine pick up. Left the car for 30 mins or so, it started 1st time and all felt and sounded good

I did check the plugs tonight, seem ok, but sooty. Which is odd as they are only a couple of weeks old, gap is good

So I’m a little confused to what caused the poor engine performsmce

Car is 1974 non modified

Thanks

 

[bugsymike]

Hi all
So went for a longer drive today, all going well. Then on the return journey came to a roundabout, slowed down, got a bit of a misfire and then a drop in power and a very hesitant engine. It picked up and on I drove. Then just when I got to the house as I slowed to enter my garage, revs dropped off, very hesitant engine, lots of fluffing and puffing from the engine. No matter of using the throttle would make the engine pick up. Left the car for 30 mins or so, it started 1st time and all felt and sounded good

I did check the plugs tonight, seem ok, but sooty. Which is odd as they are only a couple of weeks old, gap is good

So I’m a little confused to what caused the poor engine performsmce

Car is 1974 non modified

Thanks

Does it smell rich at the exhaust pipe, like a car with the choke out?
After a run the plugs should have no soot, just a nice maybe light brown colour with clean electrodes.

 

[Kiltedboarder]

Yeah it does have a bit of a fuel smell when it’s running. As I say plugs very sooty

 

[bugsymike]

Yeah it does have a bit of a fuel smell when it’s running. As I say plugs very sooty

Carb flooding, dirt in the needle jet, float height adjustment, I have even had perforated float.

 

[Kiltedboarder]

Thanks, I’ll need to get the carb out and take a look when I get a bit more time. One for an evening or weekend when the weathers bad. Currently using the good weather to sort the garden and half way through a new deck. So it’s a building site out there. Kids and wife not happy they can’t use the garden so that takes priority

 

[Goldnrust]

As the issue only showed when you’d taken the car for a longer run that usual, and got the engine really hot, it’s likely to be a heat related issue.

I would recommend checking your valve clearances, if they have closed up a little that can cause the same symptoms you experienced. It happened to me a few weeks back.

The ignition system components are also known to not like the heat, might be worth checking the condition of the coil and condenser.

Another possibly would be if the breather In the fuel tank cap was blocked, as you drive for a long time and use more fuel if it cannot draw in fresh air to replace the fuel it will draw a vacuum in the tank which stops the fuel pump from sucking.

 

[bugsymike]

As the issue only showed when you’d taken the car for a longer run that usual, and got the engine really hot, it’s likely to be a heat related issue.

I would recommend checking your valve clearances, if they have closed up a little that can cause the same symptoms you experienced. It happened to me a few weeks back.

The ignition system components are also known to not like the heat, might be worth checking the condition of the coil and condenser.

Another possibly would be if the breather In the fuel tank cap was blocked, as you drive for a long time and use more fuel if it cannot draw in fresh air to replace the fuel it will draw a vacuum in the tank which stops the fuel pump from sucking.

I would agree with you apart from the running rich smell and sooty plugs.

 

[Goldnrust]

To play devils advocate, smelling rich can also be a misfire, and sooty plugs is not uncommon on old engines which might use a little oil or where the carb is a little out of tune.

What would not make sense with a carb tuning problem, is the fact that after 30 mins rest the car started and performed normally.

If we were looking for a carb problem then debris in the float chamber, causing intermittent blocking of jets / the float needle, is a possibility.

But given how many recent threads on here with cutting out issues have turned out to have nothing to do with the carb, that would not necessarily be my first thought.

In the long term, obviously sooty plugs isn’t great, and it never hurts to strip the carb down and make sure it’s clean and working properly, before adjusting the idle speed and mixture settings.

 

[bugsymike]

To play devils advocate, smelling rich can also be a misfire, and sooty plugs is not uncommon on old engines which might use a little oil or where the carb is a little out of tune.

What would not make sense with a carb tuning problem, is the fact that after 30 mins rest the car started and performed normally.

If we were looking for a carb problem then debris in the float chamber, causing intermittent blocking of jets / the float needle, is a possibility.

But given how many recent threads on here with cutting out issues have turned out to have nothing to do with the carb, that would not necessarily be my first thought.

In the long term, obviously sooty plugs isn’t great, and it never hurts to strip the carb down and make sure it’s clean and working properly, before adjusting the idle speed and mixture settings.

Trouble is the older we get the more problems we see, which gives a wider option list of solutions.
Also not standing beside the vehicle is limiting too.