Mysterious Engine Failure - Ideas, please

[Bruce Nicholls]

I had a similar experience on a brand new Renault 5 many years ago. After much investigation it was the coil. The insulation broke down after the engine had been running for a short while. 8 miles sounds about right.

[AustinWood]

Is the vent on the petrol tank clear? If it isn't a vacuum can be created in the tank preventing fuel being drawn out. Try running with the filler cap off.

[Terry McGrath]

My Alvis 12/60 would cut out for no apparent reason and then start normally after 15 mins. Everything was checked an appeared normal. Being in the middle of nowhere I eventually had to call the RAC. He eventually found that the coil had rested for years on a protruding bolt-head which had worn a tiny hole through the bottom. This allowed cooling fluid to escape which caused overheating and failure, but would work again when cooler. Not in a month of Sundays would I have found it!

[Malcolm Parker]

Another possible cause could be the distributor, some of the internal electrical connections are not always obvious and failure is not always down to the points, condensor or rotor arm.   It may be worth fitting a spare distributor that you know works okay.
Is the engine properly earthed?  On some Austins with rubber mounted engines it has been found that the choke cable is providing the only earth.

[Peter Sweeney]

I had a similar problem after the 2012 JOGLE 5-8 miles fuel not through. Petrol pump too hot to touch. doused in water started again. Seemed it was a mix of advanced ignition and ethanol in petrol causing the heat and fuel vaporising.

[Graham Barker]

Thanks for all the suggestions.  It 's mind boggling to hear how many things I should  look at. A local forumist, Graham Ockleston, has offered to come by and help me work through the suggestions. 
Regards 
Graham.

[dickie65]

Just to add another possible cause I have had an ignition switch fail which caused an miss fire and engine stopages. As I was a long way from home I hot wired the coil straight from the battery which kept me going, but it meant opening the bonnet to stop the engine.

[andrew34ruby]

 It 's mind boggling to hear how many things I should  look at.

If we listed all the possibilities it would take more than a lifetime to work your way through them all. And as you replaced parts you might fit some faulty parts, adding to the problem.

Never mind all the possibilities, you need to start to diagnose. 

First, do you get a good strong spark from the coil? If not use a simple test light to check the circuit through the ignition switch, coil and the points to earth.

If/when there is a good spark from the coil, check for a spark at a plug.

Test the rotor arm for a short through it.

If/when sparks to the plugs seem good, try to start the engine with and without choke and throttle.

If it doesn't start, then squirt a spoonful or two of petrol straight into the air intake. If that makes it start momentarily then start to check for petrol from the pump.

If it still hasn't fired at all, then remove the spark plugs and are they sooted up?


Try not to dismantle things unless you need to. Try to be logical and think it through. Try not to swap parts.

I did this for a living for over twenty years, can you tell?

[Graham Barker]

Andrew,
Thanks for your calming comments.
Cheers
Graham

[bob46320]

I had a similar problem, OBVIOUSLY fuel, but turned out to be IGNITION !! Remove your points, grind off any spikes and hollows or replace. Make sure the insulating washers and nut are in the right order. Also check the wear in the top bush of distributer. If badly worn, the points gap can change significantly when engine runs / warms up.