Genuine spark leads?

the genuine leads are needed on later fords with very high voltage ht and wide plug gaps plus lean running. older systems are much less fussy. it would be normal to get a shock while groping around any ignition system while it is running. it is not a good thing to do as it may lead to death if you are unlucky.

have you checked the valve clearances? vacuum leaks are easiest to check for using spray carb cleaner. if the misfire is regular then test by shorting out each cylinder in turn and note which gives the least change to engine note, then research that cylinder. I would do this by exposing one end of the ht leads and use an insulated metal probe with a lead to earth, I converted an old screwdriver by attaching a lead with a crocodile clip.

Ah, good to know. I survived :)

No, how likely is that to be a problem? I'm not a great fan of things where gaskets are involved, as once I've got them off I can't be 100% sure of getting them back on again and sealed, if I can buy the rocker gasket at all. (that is the right name? Mazda EPC calls it 'Gasket, Head Cover', and someone else calls it a 'valve cover gasket'). Though there's one on ebay for 7 quid so maybe worth a punt. I seem to be buying half of ebay at the moment!

I'll try that.

That's a neat trick. Think that will be my first point of checking.

BTW, according to Mr Haynes the engine note is supposed to change when I pull out the engine side of the PCV (positive crankcase ventilation) valve and stick my finger over the valve end. Well, I can feel a vacuum and the ball bearing rattles, but no engine note change. Vacuum leak, dodgy valve, or everything normal? A new valve is $1 but costs $20 post and takes 2 weeks to come from the US: nobody in this country seems to even know what a PCV valve is :(

Theo

Tight valve clearances can ruin the tickover without impacting performance very much. Valves tend to recess into the head and close the gap nowadays due to the changes in fuel composition.

the engine should be pulling some of its air through the pcv (which is a service item on most cars) therefore blocking it should change the engine speed/note.

What CO reading do you have at normal hot idle?

FWIW it was running fine until the fuel filler rusted through and started putting water and rust in the tank. Evidently the filter didn't catch all of that as I found bits of rust in the float chamber. Had the filler pipe changed, the fuel lines blasted through, a new filter and cleaned the carb. But would water in the fuel mess with the valve settings? They strained the fuel but there might be some water left: half a tank of possibly-damp fuel sat around for about 6 months and then I filled it up with fresh the other week. It's now about half full again, so there's potentially a mix of 50% damp stale fuel in there. Likely to be a problem? Shall I just drive it around until it's empty to flush it out the system?

I rang up Unipart and Eurocarparts and they'd never even heard of a PCV, and ebay UK has a grand total of 9 for all cars in existence... are they called something else over here?

Dunno... I have a cheapo CO meter (Gunson's) but it's wildly inaccurate so I'm not sure I trust it for anything other than comparative measurements. Last time I measured the CO (before the carb rebuild) it was reading from

0.9% up to 1.2% CO even though I set the mixture as rich as possible (big black soot patches on the grass). Optimal is supposed to be 2% CO.

Another stupid question: I wasn't paying attention when I took the rotor arm off. There are only two mounting screws, so it's possible I put the new one on out by 180 degrees. Would a 180 degree mismatch be a problem? On a 4 cylinder car, at any one time two cylinders are doing the same thing, right? Or does rotating it mean that cylinders 1 and 4 fire when 2 and 3 should and vice versa? If I had it rotated would that give poor idle or just make it fail to work at all?

Thanks for the advice... Theo

you need to use up all the fuel and start with fresh.

PCV also known as CVV, do you not have a mazda dealer to go to?

if the rotor was 180 out then it would not run at all.

In article , Theo Markettos scribeth thus

With the sort of voltages involved its to be expected;!.. I'd use either a further bit of good insulation like polythene sheet wrapped around it or use a pair of pliers connected to the vehicle earth!..

I'd rather expect it would have done, 20 years is a bloody long time for HT leads to maintain their composure;)..

Well have a look at it in the dark, any really serious leakage will usually show up under those conditions.

What happens if you pull the leads off each plug when the engine is running?. Usually an unchanged or little changed engine note will shown up which if any of the pots are duff..

Ta. It looks like taking the plugs out and putting them back in again has helped a bit (dodgy contact somewhere?).

Mazda have no stock of the PCV valve in the UK, so they have to backorder it from elsewhere (possibly Japan). Takes 2-3 weeks minimum, could take months if it ends up on a ship. However poking around RockAuto (the US parts place) gives a slightly more sensible shipping quote (15 quid post for 3 days) and I can get some exhaust bits too, so it's not such a bad deal.

Will run until the tank is empty and try again.

Cheers, Theo

if the manifold connector (or pipe) for the pcv valve is partially blocked then you might still get vacuum at the pcv, but not enough actual air flow through it.