Cutting out.

[rovermorris999]

Any ideas out there for this problem please?

'68 van. Driving along merrily, a few misifes, then stops. Won't start. No spark. Mate tows me home, new points and condensor. All ok again.
Until the next journey. Same thing again. Same mate tows me home. I curse the new condensor and refit the old one. All ok.
You've guessed it. Groundhog Day again. This is only happening when it gets hot so I suspect the coil. Swap for a known good one. All ok.
Yawn! Not again! Change dist cap, coil lead, rotor arm for known working ones. Starts and runs fine. This time I get it hot at home, and lo! It cuts out when fully hot again.
So what have I missed? All the connections have been broken and remade. All look fine. I suppose there could be a break in one of the leads fron the coil but they look fine and if so, why only when hot? Jiggling them makes no difference. It runs perfectly when it is running.
I'm running out of hair to tear out, what's left is grey, so any ideas please?

Thanks in advance,

Nick

[rayofleamington]

That's a tough one - you've changed the bits that give the most common failure.
Personally I'd get a multimeter (about £10 or £20+ for an expensive one) and trace the live right from the supply to the points when it fails.
You can also use a bulb with flying leads in place of a volt meter if you prefer.

There are all kinds of funny stories about cuttting out when hot (including one which did something like squirt a small jet of water from the top hose when the engine heated up which shorted one of the coil wires), so really you need to give it a good check over when it fails to see which area is the weak link.

[Kevin]

Might also be worth a look when its dark to see if anything is sparking/shorting.

[Pyoor_Kate]

I did have a failed piece of insulation give a similar fault, thing was as soon as you took it all apart and put it back together, it got moved from wherever it would get to and the car was fine. Also only happened when hot, for reasons which escaped me.

[rovermorris999]

Thanks for the replies. It's piddling down at the moment and the garage is full of conservatory so I'll have to wait for sunshine before I have another go. So much for Lincolnshire being one of the driest counties!
I'll post again when I have any more info.
Cheers
Nick

[Kevin]

and the garage is full of conservatory

You have got that the wrong way round Nick, a conservatory is for keeping the garage overspill in

[rayofleamington]

Hmm - maybe I should get a conservatory then! That way I could use the dining room for eating in

[Andy]

Apparently, sometimes this type of cutting out is caused by a blocked breather in the petrol tank.

As the engine runs, using up petrol a partial vacuum is created in the tank. This makes it more and more difficult for the petrol pump to pump fuel from the tank and the engine stalls.

The check is to run the engine until it cuts out, then remove the filler cap. A blockage will be accompanied by a 'sucking' noise from the filler cap as it is removed.

Please ignore this if you've already ruled out fuel starvation
Regards

Andy

[rayofleamington]

Won't start. No spark.

probably not fuel starvation then, but it is one to bear in mind on any car if it cuts out after a repeatably similar amout of driving. I once had a motorbike do that - it didn't get me home after buying it That one turned out to be a restricted fuel inlet at the carb.

[rovermorris999]

Ok folks, here's an update. Utilising a spares car, I changed the short wire in the distributor, the points and condensor (again) and the van started first go again, ran until hot and cut out. There's no spark at the plugs, but a healthy spark from the coil to distributor lead if held against the block and the engine spun. So it must be in the distributor. LT side should be ok, yes? As it only happens when it gets hot surely it must be the condensor? I changed it again for a new old stock Lucas one. Same again. Runs fine until hot, misfires slightly then just stops. Is there anything that can cook a condensor? I don't believe 3 on the trot can be no good, including a known good one. Is there a ballast resistance wire anywhere, would this cause the problem? With the points closed and the ignition on, I get a full 12v between the -ve coil terminal and earth (+ve earth car). Is this correct? I seem to recall if a ballast resistor is in there somewhere this voltage should be 6-7 volts. Could this be the problem?

Thanks for the suggestion of fuel starvation. That was my first thought. I pulled off the pipe at the carb and the pump sends out a healthy stream of fuel and the float bowl is clean.

This really is doing my head in! Minors are meant to be simple!

Cheers,

Nick

[rayofleamington]

LT side should be ok, yes? As it only happens when it gets hot surely it must be the condensor?

The condenser is on the LT circuit so if you get a spark fom the coil it should be fine.
The better way to check that the coil is giving an output is to use a sparkplug lead and a sparkplug. This way you should know if you are getting a spark big enough to jump across the sparkplug gap.

Rotor arm surely needs checking again! Also the dizzy cap and leads.
If the coild is provding the output for a spark it has to be getting stopped or grounded somewhere!

As a real long shot - are you sure the rotor arm is well lined up with the pickup in the dizzy cap at the point of firing? If it is just off the end it could cause unreliability - more so when hot.

[sjstyles]

Sounds like a nightmare.

Im probably way off the mark here but do you have a temperature gauge fitted, if so might that be shorting out when hot?

It does sound like something could be just expanding and contracting though breaking an electrical connection. Fat lead on back of coil maybe, or where it goes in to the top of the distributer cap?

It can't be eating condensers because you refitted the first one which was deemed to be broken.

Might want to try a new cap and rota arm maybe.

Probably wasn't much help, all the best anyway!

[vanboy]

i had a cutting out problem like this before and after changing half the car realised there was no earth strap on the engine/gearbox,fitted one and it did not ever cut out again.?

[rayofleamington]

no reply since 19th August so I guess it's fixed.... (I'd bet money on the rotor arm or dizzy cap)

[Kevin]

realised there was no earth strap on the engine/gearbox,fitted one and it did not ever cut out again.?

Yes thats one of the less obvious faults that caught me out once as well, although in this case I bet Ray is right.

[tapbuster]

check that the pivot point for the contacts is not shorting out i.e. the spring is not sliding down the shaft, because the insulater has been put on upside down. check for shorts to ground on the wiring next time it fails, should only short out if points are closed.

[aupickup]

i had a tr6 once and the gearbox earthstrap was not there.
fitted one and no problems

[tapbuster]

When the engine dies, does it cut out instantly or coughs n splutter? I cuts out dead, then its an electrical fault, look for short cicuits on ignition system wiring. If it coughs n splutters the it more likey a fuel problem.

[rovermorris999]

Holy resurrected threads!

I've just posted another topic and noticed I was ignorant enough not to finish off this one (I hate it when people do that! My excuse is I was up to my eyes in building work). I finally solved the misfire. It was..... (drum roll) the plugs leads! They were nearly new and yet replacing them with an old 'knackered' set saw the old bus run as sweet as a nut.

[ASL642]

Oh well better late than never! - hope all the building work is completed now. This post may help someone else with a similar problem in the future.