Switch on LT wire to coil

[BMWChris]

Hi,

my engine has a marginal bottom end. To help protect it I allways spin the engine over for sometime when cold to build-up oil pressure before I use the choke. Obviously this doesn't work when the engine is warm as it starts straight away so I put a switch in the LT wire to the coil so that I chould spin the engine on the starter and then switch the switch once pressure had built-up. This didn't work 100%. Although the engine won't run with the switch off and will stop running when you switch the switch, if you spin the engine with the switch off it will fire and run for a few seconds which is probably more damagine than starting and running and quickly building up oil pressure. Can the coil store a few seconds' worth of sparks? What should I do differently?

Also, I was worried that it might damage the coil. Is this true?

Car is Midget 1500 converted to electronic ignition.

Thanks

[tr7v8]

Sounds like the coil is powered off the ballast lead from the starter.

[garagewidow]

agree,convert to non ballast coil and your idea should work ok.

[Steve_D]

As said it sounds like your coil is powered from the ignition and the starter.
This is to help cold starts. During a cold start the starter pulls heavy current and pulls down the voltage on the whole car so your coil is getting a low voltage and not sparking as well as it might.
To overcome this your coil will most likely be a 9 volt coil and, during normal running, powered via a ballast resistor or resistor wire from the ignition switch. During start the coil is powered direct from the starter solenoid i.e. approx 12volt going to a 9volt coil giving a nice big spark.

For your switch to work it must be fitted between the coil and the two wires coming to it or alternatively fitted in the wire between coil and dizzy.

Steve

[tr7v8]

garagewidow said:

agree,convert to non ballast coil and your idea should work ok.

Nope, the coil is nothing to do with it. It is the wiring to the coil. The starter feeds the coil when turning through a ballast resistor & that is where the feed comes from to make it start.

[garagewidow]

yes but by converting you can do away with the ballast wire altogether so only need one wire to feed the coil.

[Yuxi]

tr7v8 said:

garagewidow said:

agree,convert to non ballast coil and your idea should work ok.

Nope, the coil is nothing to do with it. It is the wiring to the coil. The starter feeds the coil when turning through a ballast resistor & that is where the feed comes from to make it start.

Nope, the starter feeds the coil when turning through a plain wire, the coil is fed through the ballast resistor once the key is realised from the start position.

Steve D has said it all, put the switch between the coil and distributor.

[anonymous-user]

In my youth I've run loads of cars with a switch in the coil -ve, shorts it to earth, never burnt out a coil, hide the switch made a wonderfull anti theft, add onther hidden switch in the fuel pump supply, save a fortune on a car alarm.