Misfire When Hot / Best UK Supplier for Pertronix

[Mark S]

On a run on Sunday, the Stag started to misfire slightly after around 10 miles and gradually got worse, misfiring every time I tried to accelerate. Got home,switched off then a couple of minutes later the car refused to start, cranking and didn't even attempt to fire. Tried again an hour later, started straight away, took it for a short run and it seemed fine. So I thought coil overheating.

New coil fitted today, went for a long run, same misfiring getting worse then failed to re-start when hot, ok later.

I'm not suspecting fuel pump (Electronic SU). I've never had hot starting problems before, the car cruises ok so my thinking is it's likely ignition.

I replaced my points with a Cray Bell & baseplate unit bought from a show around 7 years ago and it has worked perfectly so I'm suspecting this is the problem when getting hot. I assume it's similar quality to Accuspark/Sparkrite. Can these fail like this or do they either work or not and my problems lie somewhere else.

All experiences of how these units have failed or advice on where else my problems might be would be grateully received.

Can anyone advise the best place to buy the Pertronix LU-181A kit? I can't find a Uk supplier and import duties/postage from the USA seems expensive.

Thanks.

Mark.

[Matt Cook]

I got my Pertronix here: http://www.americanmotorfactors.com/contents/en-uk/p206_Triumph_Stag_70_to_77_Lucas_Distributor_35D8. html

Cheaper than Pertronix UK direct.

Also check rotor arm, I’ve used the one from LD Parts http://www.ldparts.co.uk/shop/shop.php?c=viewproduct&pid=1273&cat=3&maincat=1&st art=0&sid=sid502e2f12f5695468ae5fd1c0bd7f201a
But it looks like they are out of stock.....

[richardthestag]

misfire and non start when hot is something that I had when the mk2 ballast resistor wire broke on my stag. I diagnosed it as being the root cause by running a 12v feed to Coil +ive during the no start period.

It fired straight up. I ordered a solid state mk1 ballast resistor and ran a 12v ignition controlled feel to it.

More recently the ignition an ancient Piranha p8 system started to misbehave. Powerspark came and went quite quickly

Pertronix I bought direct from UK.

Could have saved a couple of quid by importing from the land of the free but my car was totally immobile at the time.

[Mark S]

Thanks Matt and Richard.

I was running points before and suffered misfire but it was different, more of a cough and lurch pulling out of junctions but no starting issues. Fixed by fileing the badly pitted points (yes, i know they have a surface coating) and setting up but only lasted a few hundred miles before needing to be done again. Even new points and condenser only lasted 1000 miles.

I eventually decided to go electronic because a quality pair of points and condenser was as expensive as the Cray Bell and, 80000 miles of wear in the dizzy/baseplate, unstable timing and a tacho needle all over the place at tickover, regular fettling and setting up etc just wasn't worth the hassle.

I'll have a look at the ballast wire first. and check the running and cranking voltages to the coil. Is the ballast bit in any particular location or is it just a piece of resistance wire? The insulation on one of the coil wires is a bit brittle but it is over 40 years old.

Thanks,

Mark.

[Matt Cook]

On early cars the ballast resistor is a separate resistor, on later cars it is a resistance wire built into the loom.