Very intermittent fault

[Stevearniepalmer]

Hi All
I posted some time ago about an intermittent fault which I still have
Basically it’s this .
I have a1967 4 door nothing special but goes along nicely.Ive spent some money over the last few years getting it to be a bit more reliable.New fuel pump, new coil ,new alternator, serviced Every year.

This last year did just over 2000 miles .Just been MOTed and full service and it sounds and runs lovely.
Anyway the fault I have is this, when I’m in traffic stop starting as you some times have to do I engage first gear to set off and go through the gears the engine is not happy and there is very little acceleration top speed 30 mph.
Pull over rev engine all good to go.Went back to garage this morning and they had a look adjusted timing as it was set a little bit slow, checked brakes all good .On way back from garage the same thing happened .I slowed down at a set of traffic lights into 2nd set off and very little power got to 30 mph but had to pull over.Let the engine run put foot on accelerator set off again all was fine.It doesn’t happy at every junction but has happened every journey at least once.

The garage I use is a really good one the owner has a classic car and he and his colleague are really good blokes etc.They are stumped .
Sorry this message is long but if anyone can help I would be grateful.
Steve

[Monty-4]

Well well, it sounds like it must be a fuelling or ignition issue given the intermittance. I had a very similar problem and it was the fuel pump points needing a clean which led to fuel starvation under certain conditions. If you have the old pump or a spare it might be worth trying. Inevitably it will be something that simple (as there is nothing complex on these cars) such as:

- Carb dashpot oil.
- A sticky choke mechanism.
- Points dirty or incorrectly gapped, distributor cap contacts worn/corroded, a dying condenser, rotor arm worn/corroded.
- Fuel pipe from pump to carb breaking down.
- Gunk in carb body.

Given you don't describe the engine 'missing' or 'misfiring' I wouldn't suspect the HT leads or spark plugs but they are an inexpensive thing to change (or at least check the gap on the plugs) if you run out of other theories.

[simmitc]

When trying different ideas, change one thing at a time so that when you do fix it, you know what the problem was.

Could you just confirm that there is no misfire. Also, if it is safe to do so, when the problem occurs, press the clutch to disengage the drive and see if the engine revs freely, or whether you have to pull over and wait until it works.

I am wondering whether you have a bit of debris in the float chamber that is blocking the jet. I had this once when the O-ring on the end of the jet began to break down and a small piece, still attached to the rest of the ring, occasionally got sucked over the end of the pipe. In your case, I'm not sure why it would happen when you slow at a junction, but you never know.

Also check the operation of the vacuum advance unit in the distributor.

[Stevearniepalmer]

Hi thanks for replies .
There definitely isn’t a misfire at all. It doesn’t happen at speed , in fact it feels and sounds as if the engine would go all day.It only seems to be a problem when at low speed then setting off again .And only occasionally

[Stevearniepalmer]

If it is a fuel type problem would it help at all to pull the choke out slightly or would that make it worse.
As you can probably tell I am absolutely no good at all with the mechanics of any sort.
After all this nonsense finishes with the lockdown I do have a few people who might be able to help me at my branch of the owners club.
Thanks again
Steve

[simmitc]

Choke won't do any permanent harm, either it will ease the problem or make it worse. I'll turn the question round and aks whether using the choke does make it better or worse? It could provide a clue.

Immediately before the problem occurs, have you been using the brakes to stop the car?

Is there a safe piece of road where you could repeatedly try stopping and starting to replicate lots of junctions in a short space of time? Just looking for ways in which you can test ideas without having to wait until a potentially awkward situation.

[Stevearniepalmer]

Yes it does always happen just after brakes applied.The brakes have been checked and all a ok.I have a servo fitted .Most of the time its when ive been slowing down and then need to put my foot on the gas again quite quickly say in traffic or on a roundabout.Its never happened when at speed.

[pgp001]

It does sound like the front calipers are being a bit lazy to release the discs when you have been braking.
Has the master cylinder been modified and had the seal removed for use with a servo.

Try jacking the front wheels off the ground and getting someone to apply the brakes while you try and turn the wheels, you should see fairly quickly if they are sticking on when the pedal is released.

Phil

[kevin s]

Could be the piston i the carb sticking, with the air cleaner off see if it rises and falls freely.

[Stevearniepalmer]

Hi All
Thanks as always for your helpful suggestions.
I went out today for a good drive and
As suggested found an empty road
In which to replicate the stop start of urban traffic
That I was having problems with.
Of course Audrey was having non of it and behaved
Perfectly throughout
So either the problem has sorted itself out
Or I shall just have to wait and see what happens.
I’m thinking that it’s a fuel problem as
For example the vacuum advance is very very old looking
And I’ve had problems before with
Parts that have needed to be replaced .
She did less than 2000 miles in 10 years
So it was rather a shock when I bought her.
I will let you know if it happens again
Steve

[Myrtles Man]

Written in blank verse?