Voltage at coil and when running, Help Please!

[berni29]

Hi There

My plus 2s has 10 volts at the coil when the ignition is on, with the engine not running, and 6 or less when it is running. The battery is new and spins the engine really well, and I have 12 volts at the solenoid. The spark looks weedy to me and will jump no more than half an inch either at the coil or on each lead. I have tried another (old) coil with no change in the results. Needless to say the car does not run well, hence my search for the reason.

Are the voltage readings normal? The electrical side of the car is a bit of a mystery to me!

Many thanks

Berni

[Jason1]

Hi Berni

The ballast resister would drop it down to 6v, so no problem there. You say you swapped the coil so it is unlikely you have two naff coils?

If the spark is weedy check the CB dwell angle with a dwell meter (Halford Gunson make a cheap one). Are you running CB?

If you are then altering the CB using feeler gauges sometimes gives you false readings if the dizzy cam lobs are worn or it the shaft is worn.

Si just bought a new coil, ask him if you can borrow his coil and leads

Jason

Ps

I still have not got around to fitting the wheels and headlamp I got from you, maybe in the spring?

[berni29]

Hi Jason

Thank you for the reply and the suggestions. How do I know if I have a ballast resistor? I cannot see anything obvious. I do have another (blue and white) wire right next to the +ve side of the coil but this is not connected to anything. I have points and as far as I know the distributor is in very good condition.

I used to have one of those gunson things that let you measure the distance that the spark was jumping against a scale, thereby getting a handle on the condition of the system, but I must have driven over or lost it. No surprise there.

At the moment the car takes ages to start and runs like an absolute pig until warm. The timing is right, and I have used the colourtune on the car, so things are thereabouts on the mixture. I have used a synchrometer to balance the carbs, so ditto there. There is a very strange clicking/tapping sound that comes and goes. It sounds like arcing to me, but there is no evidence, and the sound does not dissappear when removing each lead in turn.

Simon does not know that I have just bought a trackrite on ebay, so I could use that as leverage against trying the coil. In fact it makes more sense to take the whole distributor, leads et all off his car and try them on mine. As far as I can remember he does not have a timing light, and I have a really good one. An offer of timing his car plus the trackrite might be enough to swing the deal.

The funny thing is that I am in the market for another set of headlamps that take the h4 bulbs. My stint in Singapore has been put off for a while, so I am getting the car ready for my yearly trip to North Wales. Seeing as a contributing factor in me crashing my last +2 were the poor headlights I do not want to risk it again!

Good to hear from you.

Berni

[Frank Howard]

Hi Jason

Thank you for the reply and the suggestions. How do I know if I have a ballast resistor? I cannot see anything obvious. I do have another (blue and white) wire right next to the +ve side of the coil but this is not connected to anything.

Berni,

I believe your car used to have a ballast resistor. It is usually mounted near the coil, close enough so that the blue/white wire can reach it. The power is supposed to come from the ignition switch, through the tach, to one side of the ballast resistor via the white ignition wire. Then it is supposed to leave the other side of the ballast resistor through the blue/white wire to the + side of the coil. It appears that a PO has bypassed the ballast resistor, connecting the white ignition wire directly to the + side of the coil. This will shorten the life of the coil (if the coil requires an external ballast resistor) as well as the points. Hope this gives you a start towards fixing the problem.

[Frank Howard]

There is a very strange clicking/tapping sound that comes and goes. It sounds like arcing to me, but there is no evidence, and the sound does not dissappear when removing each lead in turn.

Berni,

This is a big clue. I believe your HT wires are ready to be replaced. Here's another way to check them. Work in the dark. That's right, run your car in the garage with the lights off (and the door and windows open) and when your eyes have adjusted to total darkness. Look at the coil, distributor, HT leads, and plugs. In pitch black dark, you shouldn't be able to actually see these components, but you should be able to see where that clicking/tapping noise is coming from. Probably the spark has found a path of least resistance and it's not through the wires! Let us know the results of this test.

[mikealdren]

Berni,
Frank's absolutely right about the ballast resisitor.
Coils that use a ballast resistor run at a lower voltage than normal coils.
When starting, the full 12 volts are applied directly to the coil give a higher output but in constant use, this will eventually (soon) burn out the coil.
Once the key is returned to the normal running position, the ballast resistor is used to reduce the voltage to the coil.
The ballast resistor is usually mounted directly on the coil terminal, there are two connectors, one on top of the resistor and one direct to the coil.

Mike

[mikealdren]

Berni,
Frank's absolutely right about the ballast resisitor.
Coils that use a ballast resistor run at a lower voltage than normal coils.
When starting, the 12 volts applied directly to the coil give a higher output but will eventually (soon) burn out the coil.
Once the key is returned to the normal running position, the ballast resistor is used to reduce the voltage to the coil.
The ballast resistor is usually mounted directly on the coil terminal, there are two connectors, one on top of the resistor and one direct to the coil.

Mike

[tdafforn]

had the same periodic clicking sound on my +2. Turned out it was arcing from the thermostat housing to the lockheed servo (bit odd considering that the engine grounds where in good condition!). New leads and problem had gone...
Tim

[berni29]

Hi There

Thank you again for the suggestions. I have previously run the car in darkness looking for ignition leaks (not so recently though), but I must admit that I have never looked further than the distributor and leads. After hearing about the thermostat housing to servo arcing I will have another go for sure!

I will have to have a look at that white and blue wire near the coil again, and get a ballast resistor. I thought that the wire might have something to do with the switch that is on the passenger side above where your knees are. I remember attaching it to the +ve side of the coil once and burning a wire on the points out (my memory is a bit dull on that one, but I remember the smoke well). I have a gold coloured Lucas coil that I tried as a replacement to my black one, and Simon reckoned that it did not need a resistor. The engine ran a bit better with it. It did not help that I had the engine 10 degrees out on the timing. Thats what happens when you have one of those timing lights with the dial on the back and get yourself confused.

The clicking is driving me a bit nuts. I have been over the engine with a stick to my ear listening for taps with no luck. The leads are the soft silicone type and seem in good condition. Pulling each one off in turn makes no difference.

I have another distributor set up with Lumenition and different leads etc, but I could not (for some reason) get it to work this weekend so I reinstalled the existing one. I think that I will set up the lumenition off the car and see if I can see where I am going wrong with it.

At the moment the engine will idle fine once warm, but spits and misfires quite agressively (on and off) when reved. I am sure that I am loosing sparking power. Once I have tried an alternative ignition set up I will know more.

Thanks again for all your help.

Berni