question Ignition system - sanity check

[MiketheBike]

I tried to start up the 101 the other day after it being standing for a week or so. Turns over fine but would not fire.

 

Fuel is getting to the carbs judging by the smell.

 

Checked the low tension (-ve) connection at the coil, and it was not great so snipped it off and put a new spade connector on the wire.

The points had closed up, so I opened them up with the distributor adjuster and tried again. It kinda started, but when I took the distributor cap back off it was smoking, and the plastic that holds the points and runs on the cam had melted where it is riveted to the points assembly (that would explain why they had closed up in the first place!).

Swapped out the coil, points and condenser, and the same thing happened.

 

I want to make sure I connected everything back up correctly...so:

 

on the coil, terminal marked "-" connected to distributor, terminal marked "+" connected to switch (two wires).

On the points, the condensor and wire from coil is under the plastic insulator (so insluated from nut and plate holding the points, thus giving an electrical connection to the spring that holds the points).

 

I guess it could be bad condensor(s), the coil is new (not NOS).

 

When I have the distributor cap off, and turn the engine over, the points spark badly....does this suggest condensor, or could there be something else?

 

It all ran fine before the really cold weather, and when I left it standing during the snow

 

Thanks,

 

Mick

[Richard Farrant]

Mike,

 

Have you fitted a coil designed to use a ballast resistor? I have come across this before, where you have a 9v coil running with 12v though it and it melts the plastic heel on the points.

[Richard Farrant]

Had to dig out the EMER to refresh my memory, if it is a 12v system you should have a ballast resistor mounted under the coil, is it wired in and is it working correctly? I suspect the coil is not the correct type.

[MiketheBike]

Richard,

 

what a complete idiot! Me not you!

When you wrote that I thought...its a 12 volt coil, and the guy in the car shop said it was the same as the one I brought in...what could possibly go wrong.

After I read your post I went out to the garage and got the box and in the box is a piece of paper with ruddy great big red writing on it

 

 

I'll get me coat!

I'll put the old coil back in tomorrow

[Richard Farrant]

No worries, Mike, at least it is a simple fix :-)

[MiketheBike]

Richard,

 

I thought that also, but there is no ballast resistor. I assumed (badly) that the ballast was used with a 6V coil...as thats what it says in the workshop manual? I thought if it used a proper 12V coil it would not need the ballast?

 

Mick

[Richard Farrant]

Richard,

 

I thought that also, but there is no ballast resistor. I assumed (badly) that the ballast was used with a 6V coil...as thats what it says in the workshop manual? I thought if it used a proper 12V coil it would not need the ballast?

 

Mick

 

 

Mike, the problem is when buying coils nowadays, you ask for a 12v one, but what you have to watch is whether it should be used with a ballast. I found this problem on a Dennis fire engine once, the owner had several breakdowns on the road, having to call out the AA. I had a look and found the points plastic part had deformed with heat. The owner told me it had been alright until someone serviced it and fitted new points, he showed me the old ones, which were hard fibre type, obviously unaffected by heat, so checked out the coil and it had been changed sometime in the past and was not a standard 12v type.

[fv1609]

The point about a coil designed to function with electronic ignition is that it will have a much lower resistance than a coil designed to operate with points albeit at a similar voltage.

 

For example:

12v electronic ignition coil resistance = 0.5 - 1.0 ohms

12v conventional points coil resistance = 3.0 - 5.0 ohms

 

The limitation of the points is that as the current switched increases beyond a couple of amps the heat generated & sparking increases destructively.

 

With electronic ignition the power is switched cleanly & suitable power transistors are not constrained by mechanical limitations. They are therefore designed to switch a current a 2 or 3 times that which would be tolerated by a conventional points system. This is why your points were getting destroyed because they were carrying dramatically more current than they could handle.

 

More current in the appropriate coil means a greater magnetic field is stored in the coil. When this magnetic field collapses as the points open a greater HT output can be realised than in a conventional system.

 

Not familiar with 101s, but in other Rover 24v systems the coil itself is designed for 10v in conjunction with a 4.4 ohm ballast resistor.

[MiketheBike]

It looks like the coil and ballast has been replaced at some point with a non-ballast coil ("col 201 12 Volt Standard").

I will re-install that old coil and see if she fires up, but may well go for an electronic ignition system rather than mucking about with points.

Has anyone used a Petronics unit, and views good or bad?

[sirhc]

Mick,

 

Have a look here: http://www.simonbbc.com/

 

Chris

[MiketheBike]

Thanks Chris...these are cheap...great value!!

[fv1609]

I fitted a simmonbbc £15 module in my Shorland 2 years ago & been very reliable.

[fv1609]

A few words of caution.

 

This thread has got me realising that I am missing out by not using a special ignition coil with lower resistance to get more oomph out of the HT. All I have been doing is benefiting from the elimination of mechanical switching & getting a sharper cut off to the coil LT.

 

So I started looking around simonbbc's shop for a suitable electronic ignition coils. BUT all of these state:

 

However this coil is NOT suitable for our

POWERSPARK ™ electronic ignition kits

 

When you look at his packages for an electronic ignition kit & matching coil, the matching coil is in fact for standard ignition (ie points). The implication of this is that the Powerstart module cannot handle any more current than the points.

 

One of the limitations of these modules being directly fitted to the base plate is the dissipation of heat. When you follow the various views on the Britpart module, which was the cheapest when I was looking 2 years ago, the results were about 50-50.

 

The Powerspark module doesn't look that different but they do supply some heatsink compound to ensure the module dissipates heat to the baseplate effectively. I think this is the factor that gives Powerspark the undoubted success it has. The problem is that the base plate is of limited size & in an enclosed space is not well suited for dissipating much heat.

 

Attempts to expect it to draw 2-3 times more current with an electronic coil would no doubt be disasterous. The only way to use an electronic ignition coil, as far as I can see, is to either substitute a distributor designed specifically as an electronic ignition unit or utilise the Powerspark module to switch an external module capable of switching the higher current and dissipating the heat.

 

Neither of those two options appeals to me. Apart from the hassle involved, I like the look of originality when you peer in the engine bay, which is all part of the character of the vehicle.

[MiketheBike]

I have ordered one up, and had a quick chat with them...£39 all up which seems an absolute steal.

They do have sets that run with low resistance coils, but its a complete distributor (works out at about £120 delivered for the V8 version), and he says I can just use the old cap to keep it looking original...not an issue on 12V systems, but won't look nice on a 24V system I would guess.

[MiketheBike]

Finally got the beast running with the standard (non-ballast) coil and new points.

I also noticed sparking at the points, which has stopped after a third condensor swap...not sure if the "electronic ignition" coil had screwed up one of those...maybe not....where is Clive's Megger when you need it

Also, the LT lead (distributor to coil) had a broken connector...so it kinda worked ok when cranking, but as soon as there was any vibration it appeared to cut out, so re-terminated that...I think it was due to all the pulling about as there were no problems with it before I touched it.

 

Thanks for your help and pointers....look forward tp getting the module from simonbbc on Friday and retiring the points to a backup role

 

Mick

[Tony B]

Joys of the 101! :-D

[MiketheBike]

Well, the simonbbc electronic ignition install was a piece of cake. 15 minutes to install and adjust the timing and it appears to run a lot better and start better when hot.

At the price I may just but another one as a spare and keep the points and condesner as a backup backup!!!