Sparking problems

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sydley

New Member
Posts
12
Location
Northampton
V8 Auto wont start, got to the point where the coil to dizzy leads arcs to the rotor arm when turned over. I have changed the rotor arm for genuine lucas part 3 times still to no avail. Any ideas are welcome as it is becoming personnel between me and the Heap (only at the moment).
 
The h.t. lead should not short out across the rotor. This means that all, or most of the juice from the coil is going to ground before getting to the plugs, result-won't start or runs rough.
Can you confirm that:
The h.t. lead from the coil has been pulled out of the dizzy cap.
The dizzy cap has been removed.
Holding the coil h.t. lead with insulated pliers or similar approx.6-8mm. away from top face of rotor arm whilst assistant spins engine over.
Given the above is correct, there should be no arcing across if the rotor arm is o.k.
This is a standard check for the integrity of the rotor and you will find is part of the checks in the Range Rover workshop manual.
 
Done all the checks, the only thing that I havent replaced is the distributor. I was wondering if the distributor has got an internal fault somewhere.
 
The dizzy is only a mechanically driven switch with an electric/electronic trigger any fault with it would not cause a spark to jump through what is-or should be-an INSULATED rotor arm to ground. I have never had any problems with Lucas rotors, that's not to say that there could be a bad batch, in which case you are due a refund, but I have had loads of grief-until I got caught out once only, with spurious rotors.
Tell the seller of the lucas rotors that they are faulty and try a different supply source but get it from a main stealer or an independant and demand an original, not spurious.
 
I have done a continuity test across all the rotor arms and they all show up as good. I have been back to the supplier and have got somebody else onto it, will take a while to get hold of but guarantees they will be the genuine item. Thanks for all the help so far will keep you posted on the result.
 
It's a waste of time trying to do a continuity test with a multimeter or even a Megger, it won't show anything up whereas the ultra high voltage from the coil will. Apart from that, you are duplicating what is going on with the cap fitted. As you know, the juice comes down the carbon brush in the cap, onto the brass wiper on the rotor and does a small jump to the plug lead segment. Therefore, if the juice, or some of it, is taking the easier route through the rotor you will get at best a very weak spark, if any, at the plugs.
 
sydley said:
I have done a continuity test across all the rotor arms and they all show up as good. I have been back to the supplier and have got somebody else onto it, will take a while to get hold of but guarantees they will be the genuine item. Thanks for all the help so far will keep you posted on the result.
Click to expand...

Take a look at Dingocroft, they do genuine Lucas rotor arms, last one I bought was £21.00.

You might want to try putting on a new ignition amplifier. You can get one from most motor factors - it will be a pattern part (inter-mota) but will work fine. Failing that, check the air gap between the reluctor and pick-up on the dizzy base plate, easy to do. CAREFULLY remove flash shield then use a piece of ordinary 80gsm copier paper folded in half as a feeler gauge. While you're at it make sure the vacuum and mechanical advance/retard is working.

Good luck.
 
Now got new rotor arm and dizzy cap, fitted but no go. Went back through the checks again and find that the spark between the coil and the block is a yello/orange colour. am i missing the obvious here or does anybody have any other iideas.
 
There are 2 things to check.
With your multimeter check how good the earth is between the block and the negative terminal of the battery.
The ignition module has got to have a good earth to switch properly and the Primary ignition has got to be able to get to earth. If the block earth is no good then you will get your coil overheating or braking down. (orange spark)
A quick test would be to use a jump lead. Clip one end to a good earth point on the block and the other to the battery negative terminal and re run your coil test. See if you now get a good blue crack.
The other thing to check is the amount of movement in your rotor arm. If the rotor was tight, when you pull it off you can pull the dizzy shaft up with it. This pulls the springs off the bog weights and the rotor arm is then allowed to rotate more than it should.
 
Done both of them quick checks, still no difference. Is there any checks on the coil to see if it breaking down (Resistance/voltage)?
 
Typical resistance checks at the coil should be around:-
*IGNITION OFF & TERMINALS/HT LEAD DISCONNECTED AT COIL*

Between + & - (Low tension side) 0.45 to 0.85 ohms approx.
Between + & HT 11000 to 16000 ohms approx
 
Thanks for that info. The coil is OK, could the spindle in the centre of the distributor contribute to the problem,if so what is the lateral movement of the centre spindle supposed to be & could the fluctuator ring and the pickup sensor just go?
 
Are you getting fuel to the injector fuel rail?
Unlikely that the dizzy shaft has worn, in any case it would have been gradual wear and you say the motor was running before. Check the ignition timing at TDC, rotor should be pointing to no.1 plug lead on dizzy cap*. The pick up sensor being electronic could pack up.
Only solution I can think of if above fails, is to see if you can borrow a dizzy from someone and replace yours to see if it works-that should isolate/prove the point.
*You may have to turn the crank 2 revs. to get the position.
 
Have we established that there is no longer a spark jumping across from the coil lead to the rotor arm?

Have you got a manual & have you followed the diagnostic checks in it? If you haven't got a manual then download one from www.green-oval.com
 
Last edited:
What coil are you running? I remember reading somewhere that Rangies don't like "performance" coils. Genuine Lucas coils will be hard to find but check Rave/workshop manual to get details for the coil and try a new one, also change the capacitor attached to the coil ( Rimmer Bros). Of great imprtance is to ensure there is a good earth. It might be worth the trouble of disassembling, cleaning and re-making the primary earth connections under the bonnet, there is one to the chassis from the battery, one under the coolant header tank and one from the bonnet to the block.

Check continuity on the white and white with black stripe wires to and from the ignition amplifier(assuming two pin amplifier on the side of the dizzy), also check the connection of the wires on your alternator (just in case). Whilst some of these things are not asociated with the ignition circuit, Rangeys are fickle beasts and you need to make sure all is in good order.

Hope that helps ya.
 
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