Strange running problem

[James k]

Hi,
I was driving earlier when my car suddenly started to idle a bit rough, not holding a constant speed. It didn't seem to affect the drive but then again I didn't drive it that far after it started doing it. I left it for about half an hour to cool down and then started it again, it was still idling rough but revving okay. I had a look at the distributor cap for cracks and couldn't find any. I inspected the HT leads and found that one was quite rusty on the plug connector, I attempted to clean this but it's still pretty rusty. I checked all the plugs and found that they were all sooty. I've been meaning to adjust the mixture for a while since the exhaust smells a bit rich so I thought that maybe the hot weather today and pushed it over the edge and it was too rich to idle smoothly. I did the lift-pin test on the carb which confirmed rich and adjusted the mixture accordingly. After about three flats of weakening, the engine idled smoothly. I thought I might have cured it...

I've now been out for another drive in it and although it now idles smoothly (although the exhaust is popping when you go round the back), it's juddering. It feels like a stuck choke or a faulty condenser but I checked the choke and it's electronic ignition so it can't be either.

I should also mention that when I turned the ignition on after it's half hour rest, the fuel pump clicked franticly for a few seconds. Is this likely to be unrelated vapourisation or could it have something to do with it?

Possible causes I can think of are:
-That rusty lead is causing problems
-The fuel pump is somehow faulty
-The electronic ignition module has broken down

I don't think the head gasket has blown since the compressions 'felt' equal on the handle. Also, the engine has only done just over 1500 miles since a rebuild and it had both th eblock and the head skimmed so I just think that's unlikely.

Anyway, I'm currently knee deep in a Vauxhall Zafira engine (as you may know from my other thread) so I'm hoping that someone might have a suggestion based on the symptoms.

Thanks,
James

[bmcecosse]

All the usual checks -carb piston etc.Unlikely to be the electronic ignition - and is it a good 'old' coil - or a nasty new one ? If pump ticking then indeed possibly a 'fit of the vapours' . See if it's ok in the cool of the evening. How does exhaust 'smell rich '' ??

[James k]

I checked the carb and the piston and it's falling correctly, the coil is an old one. The pump ticked a lot that one time but has been ticking normally since. The exhaust just smelled of petrol and the pipe is very sooty along with the plugs. It's behaving a lot like a car with a faulty condenser.

[Trickydicky]

Have you checked for air leaks? a few people have had this recently, try spraying WD40 around the inlet manifold.

[bmcecosse]

Well -no -it's behaving like a car with a flooding carb I would say!

[James k]

How could I test for a flooding carb? Could that happen suddenly too?

[bmcecosse]

Switch off the pump? Temporarily of course.... it's what the switch is for...... Well - one use anyway!

[James k]

Switch off the fuel pump with the engine running?

[bmcecosse]

That's the idea! Does it smooth out for a good few seconds - before it obviously runs out of fuel.......

[James k]

I think I may have sussed it (and I stress 'may'!)

I just went out and ran the engine in the dark. There are constant little blue sparks between the HT and LT connections on the coil. Presumably this would cause the current symptoms?

I tried wrapping the king lead connector in gaffer tape and even jamming folded up cardboard between the two but that didn't stop the sparks.

Does this sound like it could be the cause? I assume it's due to a degraded HT lead cap or cracked coil cap.

[bmcecosse]

" current symptoms " - I like it! Yes - could well be that - certainly not helping. Clean and degrease. But it may now have 'tracked' the top of the coil.

[James k]

That pun didn't occur to me when I wrote it haha. I'll inspect the coil for cracks tomorrow. What would you suggest if it is cracked? Old coil from club spares? Or maybe I could get a shiny new Lucas coil, preferably ballast type it's certainly sparking quite a lot so I imagine it's not doing much good even if this isn't causing the problem. I am slightly sceptical though that it would have suddenly gone bad.

[bmcecosse]

Definitely the Lucas ballast coil - much bigger sparks - for a wee while... Temporary 'get home' fix is to clean as best you can - then smear oil into any tracking marks. Also remove the HT plug and clean in around there too. I appreciate you are at home - but you could try it to see if it reduces/stops the sparks jumping across. Also check - is the coil connected right way round - with the -ve (or Ign) terminal to the dizzy - assuming it's a -ve earth car ?

[Trickydicky]

Check the condition of the HT leads for any signs of cracks etc, do you know how old the current set are? I would be looking to replace the whole set, you need the ignition to be performing at its best.

[James k]

I had a look at the coil earlier and I couldn't find any cracks. The terminals were badly corroded though so I cleaned them up with sandpaper. The coil connections were also on the wrong way round. I drove it for about ten minutes and it was running fine. Now its just a case of finding out if that was as the problem or if it's just running better by coincidence. I've ordered a new set of leads too so I'll see if they make a difference.

[bmcecosse]

'Sandpaper' was hardly ideal if you used it on the plastic......hope not. But as long as it's not tracking, and now clean and dry - wait till it gets dark for another look! And pick up a 'good old coil' to carry as a spare - but try it on the engine first before considering it a spare. In fact my policy always was to fit the 'new' part - and carry the 'old' part (known to be working well) as my spare.

[James k]

I only used the sandpaper to clean the corroded metal terminals. I've just been out in the dark and it's still arcing. It does seem to be arcing to the cap rather than to the king lead connector although I couldn't find any tracks I drove the car again and it's still running okay. I'll try the new leads tomorrow and then maybe look for another coil to try. My prediction though is that I haven't found the cause of yesterday's problem and that it may be heat related. I'll just have to wait and see!

[bmcecosse]

Tracking to the cap -hmmmm. Would imagine that to be more of a problem in wet weather. Can only suggest more cleaning.... Could try a spray of electrical varnish I suppose - but shouldn't be necessary. You sure it's not a ballast coil churning out super high volts ?? Or - as I more often suggest these days -why not treat yourself to a whole new dizzy (maybe electronic) from Accuspark or Powerspark - and perhaps a coil from them too. Just make sure it's not a ballast coil.......

[James k]

It's an old lucas non ballast coil on there at the moment. I've already got a powerspark electronic distributor but I'm tempted to get a new bosch blue coil since they seem to have good reviews.

[liammonty]

It's an old lucas non ballast coil on there at the moment. I've already got a powerspark electronic distributor but I'm tempted to get a new bosch blue coil since they seem to have good reviews.

I'd second that - I've had a few Bocsh coils that I've put on my VW and Minors over the past 12 years or so, and I've never been let down by one. I have, however, been let down by numerous other ones, both brand new, and indeed 'good old Lucas' ones!