Help needed, no spark at plugs

Help........................

driving home last night went round a roundabout engine died and now there is no spark at the plugs at all.

so its a 3.9 NAS disco 1 auto

so far replaced the coil and its giving a decent spark from the king lead to ground when cranked but nothing at the plugs, it has new leads , new rotor arm and gen dizzy cap.

I dont understand what could have happened if there is a spark going from the coil through the king lead then its entering the dizzy cap but not coming out, where the feck is it going ???? could it be a lost earth somewhere that means the engine has lost its earth, i will try and use my jump leads to earth the block to the neg of the battery. but does anybody have any other ideas.

it has been a bit damp here recently but nothing dramatic, it was running fine for a while after a few teething problems recently but why has it just decided to lose its spark to the plugs, i am completely lost on this, so as i said help.......................

i want my 300 back on the road , diesels are so much easier

Is the disruptor actually spinning when the engine turns over? The black box on the side of the dizzy working? Duff ht leads?
Im sure someone that knows more about it will be along

These are the tests that follow the ht check lead you've done.
Then you end up buying a new amp or distributor or both
Simonbbc has 35dlm8 dizzy with amp for £99. Must smear amp with heat sink grease where it mates

I assume that NAS 3.9s have an immobiliser, if so remove the black wire from the coil top and replace it with a direct feed from the battery+ and try starting the engine.
Again if the same as UK spec 3.9s the amp is next to the coil U will have to unbolt the mounting bracket to inspect it.

lANDYbrownlee said:

Is the disruptor actually spinning when the engine turns over? The black box on the side of the dizzy working? Duff ht leads?
Im sure someone that knows more about it will be along

Click to expand...

Ok rotor spins when its turned over , leads are good known leads and ive also swapped them over with the previous set that i know work and they all bell out on the multimeter.

cooltide said:

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These are the tests that follow the ht check lead you've done.
Then you end up buying a new amp or distributor or both
Simonbbc has 35dlm8 dizzy with amp for £99. Must smear amp with heat sink grease where it mates

Click to expand...

done the checks from rave but as soon as i get to test 2 which is test the coil, i get a good spark so move to 6 or whatever it is and im still left with spark from coil but not at plugs.

discool said:

I assume that NAS 3.9s have an immobiliser, if so remove the white wire from the coil top and replace it with a direct feed from the battery+ and try starting the engine.
Again if the same as UK spec 3.9s the amp is next to the coil U will have to unbolt the mounting bracket to inspect it.

Click to expand...

standard immobiliser was removed a long time ago by a PO, there is an aftermarket thing in there now but if it is engaged it wont allow the coil to energize, and im getting a good spark from the coil when i turn the key to pos 3.

on a side note the ignition key is now well and truly jammed in the ignition now but that is an older recurring problem that i never quite got round to before this more immediate problem raised its head.

the thing is there is power to the coil and it sparks away nicely to earth using the lead that feeds the dizzy cap held close to an earthed part of the motor, so i know there is a spark at that point but then it dissapears between the dizzy cap and the plugs.

so i started to strip the dizzy down earlier to see if i could see anywhere that it was tracking to earth, ive taken off the top spindle and flash shield unscrewed the magnetic pick up in there and now removed the lower plate , the one just above the bob weights and found a heat marked corner on the bottom of the plate so im thinking that is what is happening, for some reason the spark is dropping to the spindle and being discharged out of the closes point to earth which i suppose is to the body of the dizzy by the bob weights.
Had to call it a night tonight as im off to the pub to drown my sorrows, but ill get some pictures up tomorrow and you can take a look and see what you think.

I have a spare dizzy from a 3.5 i think so im going to look into sticking that in and seeing if it keeps isolation and allows the spark to go where its supposed to go, otherwise im lost lost lost, im thinking electronic might be the way to go but really could do with it back up and running by monday for work and having 2 dead discos parked up in the garage isnt going to do me any favours with the wife when i tell her i want my day car back and she has to get a lift to work.

keep any suggestions you have coming because i really dont think im at the bottom of this yet and for you chaps that have commented already thank you I was getting to the point of needing fresh ideas and calm minds looking into this because it has me completely stumped, and i am/was just getting frustrated which doesnt do anything for rational logical problem tracing.

Ok its just that I had a similar thing the engine just cut out.

Info for any other 3.9 owner reading this thread
Although I had a spark at the tip of the king lead there wasn't a spark at the plugs, all down to reduced voltage from the iffy spider immobiliser feed to the coil. The piece of wire from battery to coil got the engine running again. A protected wire link is now in place to the coil with 12v taken from the ignition switch supply at the fuse board.

discool said:

Ok its just that I had a similar thing the engine just cut out.

Info for any other 3.9 owner reading this thread
Although I had a spark at the tip of the king lead there wasn't a spark at the plugs, all down to reduced voltage from the iffy spider immobiliser feed to the coil. The piece of wire from battery to coil got the engine running again. A protected wire link is now in place to the coil with 12v taken from the ignition switch supply at the fuse board.

Click to expand...

I'll give it a go for sure once I've got the dizzy back together if it doesn't fire. Cheers discool.

right update,

Ive changed the pick up in the dizzy, the ignition module and im now getting a weak spark at the plugs, very weak though.

ive had the dizzy out so the timing needs setting , i did mark the position of the dizzy before i took it out and had the engine at tdc when i rebuilt it so its time for another genuine cap and arm and see if that will help strengthen the spark up and then out with the strobe and hopefully it might start up again. not sure how or why any of this happened but i did find a huge heat mark under the the plate above the bobs so maybe it went there fried the coil and took out the pick up?

off down to the garage shortly armed with new cap and rotor to see if i can strengthen that spark up.

Wish me luck and smoke me a kipper I'll be back for breakfast

It's fecking only bloody running again, slow and steady wins the race. Proper pleased with myself now and I learned a lot about the ignition system which I'm pretty sure will come in handy owning this particular motor.

Sometimes mine will start, other times not. Replaced the unit near the coil, and has decreased the intervals of failure, but its still there. Sometimes i need to wind it over a few times for a few seconds at a time. Pain in the a*se really. Really despise it when it fails in public. Just cant bring myself to drive anything else. lol