Old car problems...!! (A series engine woes!)

Associate
Joined
30 Dec 2008
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1,940
Hi,

I've been trying to diagnose whats causing my A series engine to run abnormally today. Drove it yesterday and it ran lovely on a long trip, topped up my oil (does drink a bit with 50 years of use :p ). Came to start it up today and needed an usual level of choke and seemed a little rough. Turned it off and cleaned dizzy and rotor arm (thought I might be running on three) and all seemed well until driving home sat at the lights the revs dropped and i had to use a LOT of choke to keep it going and ended up free wheeling with the engine off until I found a petrol station to pull into. :p Seemed fine after cooling down and restarting the engine.

I'm not sure it's temp related (happened when cold this morning and hot this afternoon). But when it shows the symptoms the whole engine feels rough and unhappy to rev, needs choke to keep it going and produces less power than normal.

I've got a few ideas I'm going to check early tomorrow morning but anyone got any suggestions for me? :D

(I'm optimistic it's nothing to do with the head/compression :( )
 
Soldato
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2 Mar 2004
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SE England
If more choke keeps it going then that would imply that you've some kind of fuel supply issue. Clogged fuel filter, dirt in carb, fuel pump on its way out, something along those lines...
 
Associate
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31 Jul 2011
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206
Sounds like it could be something temperature related, maybe coil condenser, points, plugs or leads. Something breaking down when it gets hot.

If one of those components is breaking down it will give a poor spark at the plugs, pulling the choke out will make it richer helping fuel combustion with a weaker spark.

If it was mine I would try the condenser first.

Or if it's electronic ignition, then I would try the coil first.
 
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Associate
OP
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30 Dec 2008
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1,940
inlet manifold leak?

This was one of my initial thoughts in the morning but I figured it would be a consistent problem and not so intermittent.

...Clogged fuel filter, dirt in carb....

That pair were top of my written out list for tomorrow morning alongside a sticking carb. :)

Very damp and wet lately and they are not known for their insulation, wait till its pitch black, pop the bonnet and see if there's any blue sparks anywhere whilst running

True :p

needs removed and replaced with some form of buzzy vtec lump

LOL! :p I considered a K series engine conversion but I've been saving pennies for a 1380!!

Sounds like it could be something temperature related, maybe coil condenser, points, plugs or leads. Something breaking down when it gets hot.

If one of those components is breaking down it will give a poor spark at the plugs, pulling the choke out will make it richer helping fuel combustion with a weaker spark.

If it was mine I would try the condenser first.

I did clean part of the ignition system but I'll take a closer look.

Thanks for the replies everyone, some things I had and hadn't thought of looking at!!

...(getting far too used to waking up early to fix my bloody car and raiding my spare parts boxes! :mad: )
 
Transmission breaker
Don
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In a house
This was one of my initial thoughts in the morning but I figured it would be a consistent problem and not so intermittent.

I have a monkey bike with a similar issue, When cold, it runs perfectly, however, as soon as it warms up, and the inlet manifold gets warm and expands, air slips through a dodgy gasket. So, it rides fine till the heat gets through, and creates the problem.
Could be similar :p
 
Associate
OP
Joined
30 Dec 2008
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Something simple but have you checked the oil in the SU carb, assuming you are using an SU.

Yep as I service it regularly as I use my MG daily. ;) I did check it though. :)

I have a monkey bike with a similar issue, When cold, it runs perfectly, however, as soon as it warms up, and the inlet manifold gets warm and expands, air slips through a dodgy gasket. So, it rides fine till the heat gets through, and creates the problem.
Could be similar :p
If you're chasing a manifold leak, get some carb cleaner and spray around the manifolds, the revs will change if there is a leak as it sucks in the carb cleaner.
.... you say it runs badly when hot i would then say ht leads/caps / coils

Thanks everyone for the responses. I seem to have fixed it with a good clean of the ignition system and a new set of spark plugs. The 3rd cylinder was misfiring and causing it to be lumpy and I think I'm going to have to get the head done soon as it feels like I've got another cylinder with low compression hence it stalling and misfiring.

But I have found a few things I'm going to put right elsewhere in the engine bay from investigation of the problem :p
 
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