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coil over heats[700/89] posted by donnie matheson on
Wednesday, 17 January 2001, at 4:40 p.m.
i have a 740turbo intercooler.the problem is the engine knackerd.i got a engine out of a 240,the engine is a continius injection and a points distrubiter which is different from the turbo engine.i can get the engine to run ok but the coil heats up quite hot... and once i turn the starter on the engine runs ok untill i let go of the key and the engine stops running.if i keep the starter on with the key it will run ok untill i let go of the key....please,please HELP,
Re: coil over heats[700/89] posted by Mark on
Thursday, 18 January 2001, at 10:11 a.m.
Donnie:
The replacement engine you put in you 74O is equiped with a standard (points) ignition. These ignition systems have two circuits. One for starting the car and one for keeping the car running. The Starting problem you described is caused by the ignition circuit responsible for keeping the car running is not operanting properly or in other words it is "open" and not "closed" like it should be when the iginition switch is on. Here is how it works. When you turn the key to the "ON" position power should be supplied to the positive side of the coil (check this using a test light). The voltage here should be close to 9 volts. The 3 volt difference between normal battery voltage is due to the presence of a resistor in the running ignition circuit. This lower voltage helps the points last longer (they burn up faster at normal battery voltage). When you turn the key to the start postion two things happen, battery juice is supplied to the starter to spin the motor and the running ignition system is bypassed by the starting ignition system. The starting ignition system bypasses the resistor in the other system so a full 12 volts is supplied to the points. This helps the coil and ignition system develop a more powerful spark to start the engine easier. For some reason the running ignition system is not working properly on your car and consequently stops running when you let go of the key and it retuns to the "on" position. Check the following items: 1. Ignition switch, wire to positive side of coil, check for the presence of a ballast resistor and if it is good. (these can be hard to find, some times they a a special wire integrated in the wiring harness, build into the coil or a rectangular ceramic block near the coil. You might have to run a new wire to the coil from the correct terminal on the ignition switch (if you do this make sure a proper resistor is in place). If the turbo engine you replaced had electrionic ignition (probably did) then the wiring scheme is going to a lot different from what you now need.
I suspect the coil heating up is a related problem. When you are trying to start the car more voltage ( a full 12 volts) is being supplied to the coil and therefore causing it to heat up more. I cannot be certain about this, but it in theory it sounds entirely plausiable.
Hope this helps and Good luck