My 66 P1800 wont start

[swedishandgerman]

Originally Posted by arcturus

Will the points still spark if the condenser is shot?

I understood that new condenser has already been fitted (post #10) so have eliminated that as a possibility. However, if it hasn't been changed, then you should do so.

The points screw MUST be fitted as below - please excuse the quality of this picture!



Also, that hook looking thing between the 2 x metal washers on the outside of the distributor is supposed to be the connector for the condenser

[arcturus]

That was a general question.Will points spark if the condenser is shot? Just for future reference.

[Derek UK]

I think the answer is yes. Condenser test when flicking the points should show just a tiny bluish spark, in bright sunshine, hardly noticeable. When the condenser is failing you get a much bigger, "splashy" is the description often used, yellowish spark.

"The condenser across the points helps to control arcing at the points, which would soon destroy them, and also makes the spark a higher voltage by creating a resonant (ringing) circuit with the coil winding. All we really need to know is that without the condenser, the spark would be pretty weak."
From: http://www.speedyjim.net/htm/spark.htm
Therefore weak spark = poor/difficult/no start.

So, a failing condenser would allow a lot of arcing at the points causing damage. The spark jumps across the gap in one direction causing the pip and pit problem which used to commonly be fixed with a special thin "ignition" file. This situation can start when the condenser starts to fail.

[CLIVERALLY]

Did not get chance to have another go. Today is my wedding anniversary so dare not disappear to the garage .will try all the tips tomorrow......just hope the thing starts

Will keep you posted

[arcturus]

I still can't get my head round the fact that opening the points switches something on. Usually it's the other way round?

[Derek UK]

Read the quick review in the link in my last post. If the points are shorting out, they can't cause the break in the circuit which allows the coil to discharge the pulse to make the spark at the plug. As the illustration shows the points are in a ground part of the circuit, with the condenser damping/reducing the spark caused when the points open.

[arcturus]

I know that it works but just can't get my head around it. Just thinking about it gives me a headache

[123GT-AMAZON]

Originally Posted by arcturus

I still can't get my head round the fact that opening the points switches something on. Usually it's the other way round?

here is another way to help get your head round things

How Automotive Ignition Systems Work

System Parts

Automotive ignition systems are made up of several key components. The trigger device is the ignition module or points, and these supply energy to the coil. The ignition coil multiplies the energy supplied by the module and supplies that energy to the distributor cap and rotor. The spark plugs receive this energy from the cap and rotor through the ignition cables or plug wires and provide a spark to ignite the fuel.

Each of these is important to the operation of the ignition system, but to really understand how the system works, some basic theory is needed.

Theory

Over the years, the way in which the coil is triggered has changed, but the theory is the same. The theory of Magnetic Inductance says that when a current is passed through a conductor, a magnetic field builds around that conductor. When the current is stopped, the field collapses and a voltage is induced into the conductor by the collapsing magnetic field. If another conductor is placed in close proximity to the conductor, and the current is turned off, the voltage will be induced into that conductor as well. We also know that if we form the conductor into a coil, we can strengthen the magnetic field. The stronger the field, the stronger the induced voltage. This is how an ignition coil works. By turning current off and on to one coil, we induce voltage into a second coil.

How it Works

Start with a coil of wire. Passing a current through a coil of wire causes a very strong magnetic field to develop around that coil of wire. This is called the primary side of the coil and is a coil of a few turns of thick wire. Inside this coil, place a second coil made up of many turns of fine wire. This is called the ignition coil secondary.

One end of the primary coil winding is attached to ground, while 12 volts is supplied to the other end of the coil winding. A strong magnetic field is developed. Then, the ignition module, or points set, turns off the current, and the magnetic field collapses around the secondary winding inducing voltage into that winding.

That voltage is then carried to the coil tower on the distributor cap. Inside the cap, a spinning rotor picks up the voltage and routes it to the appropriate plug wire. The voltage travels down the plug wire to the spark plug, where it jumps across the gap and ignites the fuel. This is the function of a distributor type ignition system.

Later model cars use a distributorless system, and each cylinder has its own coil. The function is the same, except that each coil is triggered by a transistor in the on board computer that turns off current to that coil's primary winding.

More info .....

Most four-stroke engines have used a mechanically timed electrical ignition system. The heart of the system is the distributor. The distributor contains a rotating cam driven by the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, the spark plugs and wires linking the distributor to the spark plugs and ignition coil. (see diagram Below)

The system is powered by a lead-acid battery, which is charged by the car's electrical system using a dynamo or alternator. The engine operates contact breaker points, which interrupt the current to an induction coil (known as the ignition coil).

The ignition coil consists of two transformer windings sharing a common magnetic core—the primary and secondary windings. An alternating current in the primary induces alternating magnetic field in the coil's core. Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings. For an ignition coil, one end of windings of both the primary and secondary are connected together. This common point is connected to the battery (usually through a current-limiting ballast resistor). The other end of the primary is connected to the points within the contact breaker. The other end of the secondary is connected, via the distributor cap and rotor, to the spark plugs.
Ignition Circuit Diagram - Mechanically Timed Ignition

The ignition firing sequence begins with the points (or contact breaker) closed. A steady charge flows from the battery, through the current-limiting resistor, through the coil primary, across the closed breaker points and finally back to the battery. This steady current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark.

As the engine turns, so does the cam inside the distributor. The points ride on the cam so that as the engine turns and reaches the top of the engine's compression cycle, a high point in the cam causes the breaker points to open. This breaks the primary winding's circuit and abruptly stops the current through the breaker points. Without the steady current through the points, the magnetic field generated in the coil immediately and rapidly collapses. This change in the magnetic field induces a high voltage in the coil's secondary windings.

At the same time, current exits the coil's primary winding and begins to charge up the capacitor ("condenser") that lies across the now-open breaker points. This capacitor and the coil’s primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor’s electric field and the ignition coil’s magnetic field. The oscillating current in the coil’s primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit’s energy is consumed.

The ignition coil's secondary windings are connected to the distributor cap. A turning rotor, located on top of the breaker cam within the distributor cap, sequentially connects the coil's secondary windings to one of the several wires leading to each cylinder's spark plug. The extremely high voltage from the coil's secondary (typically 20,000 to 50,000 volts) causes a spark to form across the gap of the spark plug. This, in turn, ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was stored in the ignition coil’s magnetic field.

The flat twin cylinder 1948 Citroën 2CV used one double ended coil without a distributor, and just contact breakers, in a wasted spark system.
Citroën 2CV wasted spark ignition system

Some twin cylinder motorcycles and motor scooters had two contact points feeding twin coils each connected directly to the spark plug without a distributor; e.g. the BSA Thunderbolt and Triumph Tigress.

High performance engines with eight or more cylinders that operate at high r.p.m. (such as those used in motor racing) demand both a higher rate of spark and a higher spark energy than the simple ignition circuit can provide. This problem is overcome by using either of these adaptations:

Two complete sets of coils, breakers and condensers can be provided - one set for each half of the engine, which is typically arranged in V-8 or V-12 configuration. Although the two ignition system halves are electrically independent, they typically share a single distributor which in this case contains two breakers driven by the rotating cam, and a rotor with two isolated conducting planes for the two high voltage inputs.
A single breaker driven by a cam and a return spring is limited in spark rate by the onset of contact bounce or float at high rpm. This limit can be overcome by substituting for the breaker a pair of breakers that are connected electrically in series but spaced on opposite sides of the cam so they are driven out of phase. Each breaker then switches at half the rate of a single breaker and the "dwell" time for current buildup in the coil is maximized since it is shared between the breakers. The Lamborghini V-12 engine has both these adaptations and therefore uses two ignition coils and a single distributor that contains 4 contact breakers.

A distributor-based system is not greatly different from a magneto system except that more separate elements are involved. There are also advantages to this arrangement. For example, the position of the contact breaker points relative to the engine angle can be changed a small amount dynamically, allowing the ignition timing to be automatically advanced with increasing revolutions per minute (RPM) or increased manifold vacuum, giving better efficiency and performance.

However it is necessary to check periodically the maximum opening gap of the breaker(s), using a feeler gauge, since this mechanical adjustment affects the "dwell" time during which the coil charges, and breakers should be re-dressed or replaced when they have become pitted by electric arcing. This system was used almost universally until the late 1970s, when electronic ignition systems started to appear.

kind regards
robert

[arcturus]

So when the field collapses after the points open the energy dissipates itself through the condenser to earth,ie spark plug? I would love to see a graphic of this with the two circuits, one to the coil and return to battery, and two, new circuit to earth as points open. I can understand how things work mechanically but struggle with abstracts.

[Derek UK]

No, when the points open the collapse of the field causes the pulse to discharge down the coil king lead to the distributor where it's routed to the relevant plug by the rotor.